The brain's memory center may come "prewired," rather than being built from scratch after birth, a new study in mice finds.

The research, published in April in the journal Nature Communications, offers a new perspective on a long-standing question in neuroscience: Does the brain begin as a blank slate and build memories by adding connections through experience, or does it come with built-in wiring? The new research focused on the hippocampus, a seahorse-shaped structure deep in the brain that's essential for forming memories.

Rather than supporting either theory directly, the research points to the latter idea but adds a significant twist.

The researchers focused on a region of the hippocampus called cornu ammonis 3 (CA3), which plays a central role in storing and recalling memories. A trait known as plasticity enables neurons within CA3 to continuously strengthen and weaken their connections and thus strengthen or weaken different memories.

The team examined mouse brain tissue collected shortly after birth, during adolescence or during adulthood. They found that early in life, hippocampal networks are densely wired, with many neurons hyperconnected in a seemingly random pattern. As the brain matures, these haphazard networks become sparser yet more structured as connections are pruned. This pruning begins soon after birth, with significant declines in connectivity by adolescence.

The finding discounts the idea that the hippocampus starts out as a blank slate, or "tabula rasa."

"We find, in a nutshell, that the system is not a tabula rasa, as we thought originally, where you can just write information and then at some point, this information fills the system," said study co-author Peter Jonas, a neuroscientist at the Institute of Science and Technology Austria. "Rather, it starts out as a tabula plena [full slate] and then becomes more sparser and specifically connected."​​

This pattern may help to explain why we remember so little from infancy.

Memories are thought to be stored within networks of neurons that fire together, representing specific experiences. In a young brain, however, these connections between neurons, called synapses, behave differently, the study suggests. In young brain tissue, a single input could cause a neuron to fire, the team found, while in mature networks, neurons typically require multiple inputs to fire.

Jonas said the team was surprised by not only the early pruning of connections but also how strong those early connections were. "You might think that early in development, you have poor synapses and weak synapses, but we found the opposite," he told Live Science.

This excitability comes at a cost, however: When neurons are activated too easily, different experiences can trigger overlapping patterns of activity. If that overlap is too great, the brain may struggle to distinguish one memory from another. Instead of forming distinct networks, it may generate broader, less-specific memories. In other words, the system is very active but not very precise.

This imprecision may affect behavior, too. For example, rodent studies show that young animals learn to fear an area of a cage where they received a mild shock, freezing when they return to it. But unlike adults, who freeze at that exact location, young animals also have this response in similar environments — so the memory is there, but it's not precise.

As the brain matures, neurons become more selective and require multiple inputs to fire. The result is more distinct, separate networks that translate to specific and stable memories. So in regard to the inability to recall early childhood, it may be that our earliest memories are too poorly defined to be retained in the long term.

The findings are consistent with a growing body of research on how memory develops, said Hauður Freyja Ólafsdóttir, an assistant professor at the Donders Institute for Brain, Cognition and Behaviour at Radboud University in the Netherlands.

"It's exciting on multiple fronts," Ólafsdóttir, who was not involved in the study, told Live Science. "There is plenty of developmental psychology work that suggests that memory becomes more specific with age. And so it's kind of interesting that now, at the circuit level, we're also seeing that the connectivity patterns are becoming sparser."

So what drives brain wiring before birth? That dense, early connectivity may result from a genetically programmed developmental process. Then, after birth, experience refines the wiring, Jonas suggested.

The findings do not rule out the possibility that experiences before birth leave lasting traces in the brain. But Ólafsdóttir thinks those early forms of learning rely on different neural systems than mature hippocampal circuits.

"I'm not disputing that they're there and that they have influence," she said, referencing prenatal experiences. "They leave a trace, let's say, in our brain and probably in our psychology even." But those traces may not resemble the detailed memories formed later in life.

When asked whether the connections that form before birth represent true memories or are just a byproduct of prenatal development, Jonas said, "The latter is more likely."

The "full slate" may give the brain a crucial head start by enabling neurons to quickly link different types of information, such as sights, sounds and smells. If the brain began as a blank slate, neurons might be too sparsely connected to find each other, making early communication difficult, the study authors think.

By starting with an overconnected network, the hippocampus may ensure that the necessary wiring is already in place, Jonas theorized.

This article was first published May 6, 2026.

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Scientists uncovered a link between mild heart trouble and microscopic signs of brain damage that may raise the risk of memory problems down the line.

The new study, published Monday (July 6) in The Journal of Neuroscience, did not prove that the heart issues directly caused memory problems. But it "adds to the overall picture that preserving healthy brain-heart communication is key for healthy aging," said Dr. Jan Scheitz, a consultant stroke neurologist and head of the Brain-Heart Lab at the Charité University Hospital in Germany, who was not involved in the study.

"A healthy lifestyle that protects the cardiovascular system will not only benefit the heart but also the brain," he told Live Science in an email.

The work could one day help doctors identify patients at risk of memory problems early on through routine heart-function tests, said study co-author Dr. Xia Zhang, a doctoral researcher at the Max Planck Institute for Human Cognitive and Brain Sciences in Germany.

"The broader implication is that the brain may show subtle tissue-level changes related to cardiac dysfunction before we see obvious brain shrinkage or clinical dementia," Zhang told Live Science in an email.

Early warning signs

Researchers already knew that heart and brain function are closely interconnected. Heart diseases such as heart failure, atrial fibrillation and heart attack impair communication between the heart and the brain. This can contribute to thinking problems and dementia by restricting blood flow to the brain and causing chronic inflammation.

So far, though, scientists have only studied changes in the brain in people already diagnosed with heart conditions. They haven't necessarily assessed the changes that take place earlier on.

In the new study, researchers followed 73 patients who had sought care for heart-related symptoms at the Heart Center Leipzig in Germany, some of whom had confirmed coronary artery disease and/or heart failure. They also assessed 95 people without any heart-related symptoms. The researchers measured heart function at the start of the study. Then, about 3.5 years later, they performed cognitive testing and an MRI scan of the brain to take a snapshot of its structure.

Among all 168 study participants, those whose hearts pumped blood less efficiently at the start of the study showed greater signs of tissue damage in their gray matter years later. This was true regardless of whether or not they had diagnosed heart failure.

The cognitive tests were given only to the heart-disease patients, and they assessed attention, executive function, learning and memory. Only memory showed a link to weaker heart pumping. The participants with weaker heart pumping showed more microscopic damage in memory-related brain regions, and those brain changes correlated with worse memory scores.

The degree of brain damage also correlated with the levels of stress hormones released by the heart, but this link was only seen in patients who already had heart failure.

"What surprised us most" was that subtle reductions in the heart's ability to pump were tied to later brain changes, even in patients who did not meet clinical criteria for heart failure, Zhang said.

One limitation of the study is that the researchers didn't take MRI scans at the start. That means "we do not know whether some changes were already present at the beginning of the study period," Scheitz noted. This is something that Zhang and her colleagues plan to test in future studies.

"The next step for the field is replication in larger cohorts with multiple time points, so that cardiac function, brain microstructure, and cognition can be followed more precisely over time," she said.

The brain damage flagged in the 73 patients happened in parts of the brain that are important for memory and are vulnerable in Alzheimer's disease. "These regions helped identify a possible brain pathway through which poorer cardiac function may contribute to later memory problems," Zhang said.

However, until this idea is tested directly in future studies, it is too soon to say if the heart function-related brain changes seen on the MRI scans point to a higher risk of Alzheimer's, Zhang cautioned. The team did not measure proteins related to Alzheimer's, so they cannot conclude that the patients with measurable brain changes are developing Alzheimer's disease.

The study also did not directly test the effect of exercise on heart and brain health, but the findings may help explain why regular exercise is often linked to better brain health and cognitive aging, Zhang said.

"Regular exercise supports cardiovascular function, vascular health, and cerebral blood-flow regulation," she said, "all of which may help protect brain tissue over time."

This article is for informational purposes only and is not meant to offer medical advice.

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High estrogen in the brain's memory center may worsen one's resilience against traumatic events, swaying the tendency to develop memory problems or post-traumatic stress in the aftermath, a recent study in mice suggests.

The research, published in April in the journal Neuron, explored the effects of estrogen in the mouse brain. It zoomed in on the hippocampus, a key part of the brain involved in learning and memory. Both male and female mammals produce significant amounts of estrogen in the hippocampus, despite it often being framed as a "female" hormone.

"We're so biased to think of female high estrogen, male low estrogen," said study co-author Elizabeth Heller, an associate professor of pharmacology at the University of Pennsylvania Perelman School of Medicine. But "in this local brain region, where you have local production of estrogen, actually sometimes the males are higher than the females depending on the female's cycling," Heller told Live Science. Estrogen levels in the female hippocampus rise and fall in line with the body-wide hormone cycle, while its levels in the male hippocampus remain fairly steady.

The study suggests that these local estrogen concentrations may influence one's vulnerability to memory problems following major acute stress. Although the research was conducted in mice, the authors think it likely has relevance to humans.

"I think this is highly translatable," study senior author Dr. Tallie Z. Baram, a professor, developmental neuroscientist and child neurologist at the University of California, Irvine, told Live Science.

Estrogen isn't always a memory booster

Traumatic experiences can cause memory disturbances, including difficulty remembering specific personal experiences and having fearful reactions to formerly safe, familiar situations. When these issues persist and are accompanied by intrusive memories of the traumatic event, they are classified as post-traumatic stress disorder (PTSD).

About 10% to 12% of women experience PTSD in their lifetime, compared with 5% to 6% of men. Some of that difference may stem from variance in men's and women's lived experiences; for instance, women have higher rates of sexual assault at young ages than men do. Biological differences between women and men are another potential factor, but their contribution to the phenomenon is poorly understood.

The new study highlights hippocampal estrogen as one difference that might matter. "The research has uncovered important new avenues for research on PTSD," Victoria Luine, a professor emerita of psychology at Hunter College in New York City who wasn't involved in the work, told Live Science in an email.

In the study, researchers simulated acute traumatic events by exposing lab mice to multiple stressors at the same time, including bright lights, loud music and the odors of other stressed-out mice. They ran the mice through various memory tests before and after the stressful experience and compared these rodents with a group that did not experience such stressors.

Compared with unstressed mice, the stressed-out male mice performed worse on the various memory tests, and those deficits persisted for weeks. "Even a month later, they had a memory deficit — so it's a really perseverative effect," Heller said.

A similar pattern was seen in female mice that were stressed out during proestrus, the phase of their hormone cycle when estrogen peaks and the body prepares for ovulation. Both sets of mice learned to associate certain cues with the stressful experience and avoid them, with females being more sensitive to those cues than males were.

But interestingly, female mice that were stressed during estrus, when estrogen plummets and ovulation occurs, showed resilience. Their behavior and memory remained comparable to those of unstressed mice. "The female mice that had low levels of estrogen laughed it off — they were completely protected," Baram said.

Studies suggest hippocampal estrogen levels are similar in male and proestrus female mice, while estrus females have lower levels. The researchers confirmed this using a technique called mass spectrometry, finding that estrus mice had half the amount of hippocampal estrogen that the males and proestrus females did.

In this context, that lack of estrogen in the hippocampus appeared to guard against the negative effects of stress. This finding was surprising, Baram noted, because estrogen is generally thought to promote memory function in both sexes and declines in estrogen, as seen during menopause, are tied to memory problems. That said, menopause takes place over a much longer timeline than the female mouse hormone cycle, which takes only four or five days.

A connection to DNA

Why do estrogen levels matter for memory? "Estrogen receptors directly control gene expression," Heller said. By binding to its receptors, estrogen turns the activity of certain genes up or down.

Heller's lab studies mechanisms that control gene activity in the context of psychiatric disorders. One of those mechanisms is chromatin remodeling, meaning changes in how DNA is packaged in a cell that can shift which genes can be activated at a given time. A portion of the chromatin can be "open," exposing genes to machinery that turns them on, or "closed," which typically shuts genes down.

It turns out that the high hippocampal estrogen in male mice and proestrus female mice opens up their chromatin in a way that might leave them vulnerable to memory issues ushered by severe stress. Female mice in estrus, by contrast, have a totally distinct chromatin profile that appears to be protective.

"We can see that the function of many of those [open] genes relates to synapse biology," Heller said. Synapses are the points at which different neurons meet and exchange electrical signals, and they're central to the physical structure of memories in the brain.

It may be that, in most circumstances, it's useful to have high levels of hippocampal estrogen because they "open" the chromatin, enabling the hippocampus to forge new memories quickly in response to new experiences, Baram noted. But when these experiences consist of severe acute stress, "that same plasticity, that same ability of the brain to learn, turns problematic," she said. If the results carry over to humans, women may be particularly vulnerable to these memory impacts in certain phases of their menstrual cycles or points in their lifespans when estrogen is high.

In males and females, different flavors of estrogen receptor were responsible for the stress-induced memory issues. The reasons for this difference will be a matter of future study, Baram said. Additionally, future research could attempt to pinpoint exactly where the different estrogen receptors are located throughout the hippocampus, Heller said.

The study provides a "strong demonstration that estrogens drive sex-dependent, stress-induced changes in chromatin networks which can dramatically alter neural functions like memory," Luine said. What's more, "these results present cogent evidence that sex is a powerful biological variable."

Historically, female lab animals were excluded from studies because it was thought that their hormone cycles were too complex and would muck up the findings. The field of neuroscience exemplified this trend. In recent years, the U.S. National Institutes of Health (NIH) has required that scientists take sex differences into account when designing NIH-funded human and animal studies, but progress has been slow on both fronts — and current federal leadership has signaled a lack of support for the initiative.

It's important to include both sexes in research to truly understand how the brain functions and responds to external factors, like stress, Luine said. "An important aim of this and other studies is to protect humans against PTSD," she added, and this study strongly suggests preventive treatments for PTSD might need to be tailored by sex.

Beyond PTSD, Baram thinks the research could have implications for women's risk of aging-related memory problems and dementia.

The decline of estrogen in menopause is thought to raise this risk, but prior to menopause comes perimenopause — a period with massive spikes in estrogen. The study's findings hint that if stress shows up during perimenopause, the combination of stress and high estrogen levels may contribute to memory problems. Thus, perimenopause may represent another time when women are particularly vulnerable to memory disturbances, Baram suggested.

"We need to start thinking a little bit differently," she said. "What is it about women at that stage in life that makes them more vulnerable to memory loss with aging?"

This article is for informational purposes only and is not meant to offer medical advice.

This article was first published May 4, 2026.

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Sleep could encode epileptic seizures in the brain by repurposing the processes used to solidify memories, potentially making seizures harder to treat or prevent, new research suggests. But the new study also suggests a possible way to counter the effect: using electrical stimulation to keep the brain from "memorizing" the seizure, the researchers say.

"It opens a whole new realm of therapeutic options tailored to each patient," said study co-author Vaclav Kremen, a neuroscientist at the Mayo Clinic. He added that electrical stimulation could be personalized to each individual’s unique seizure profile.

Sleep and seizures

People often struggle to store memories after epileptic seizures, and research in rats suggests this occurs because the brain’s memory storing system solidifies neuronal connections that trigger seizures in lieu of locking in memories. However, the link between epilepsy, memory and slumber hasn't been adequately assessed in humans because most of these studies involve measuring brain activity for only a few days and the research usually takes place in clinics, which don't lend themselves to a good night's sleep.

"Hospital stays can change sleep and seizure patterns because of medication adjustments, stress, noise, and disrupted routines," Dr. Erin Conrad, a neuroscientist at the University of Pennsylvania who was not involved with the work, told Live Science in an email.

In the new study, published March 4 in The Journal of Neuroscience, electrodes were implanted for months or years into participants who slept at home, allowing the researchers to collect data over a long period without disturbing sleep. "That gives a more realistic picture of how sleep changes after seizures in everyday conditions," Conrad said.

The team analyzed two groups of participants with drug-resistant epilepsy who participated between 2010 and 2011 at the University of Melbourne in Australia or between 2019 and 2023 at the Mayo Clinic in Minnesota. One group was implanted with deep brain stimulation devices that can detect and reduce seizure activity, while the other got an investigational seizure advisory system that records brain signals but does not try to interrupt seizures. The study was small, totaling 11 participants, so the findings may not be generalizable to all epilepsy patients, Kremen told Live Science. Nonetheless, the work provides clues as to how changing brain patterns during sleep could underlie the link between epilepsy and memory.

The team found that people slept approximately 24 minutes longer on nights following epileptic seizures, yet not all stages of sleep were prolonged.

Rapid-eye-movement (REM) sleep, which is important for emotion processing and dreaming, shortened by approximately 12 minutes on nights after an epileptic seizure compared with nights in between seizures. Dr. Laurent Sheybani, a neuroscientist at the University of Geneva who was not involved with the work, told Live Science in an email that "12 minutes can appear low indeed, but keep in mind that overall duration of REM sleep is not very long either" — typically about 1 hour and 40 minutes — so the drop is meaningful.

What replaces the missing minutes of REM sleep also matters, Conrad said. The team found an increase in the length and intensity of the deepest stage of sleep, called the slow-wave stage, which is key to storing memories. One hypothesis is that the brain uses memory-forming pathways to "remember" how to form seizures in the future, but the observations from this study alone can't show that's the case.

Forecasting seizures using sleep patterns

In future work, the team needs to determine whether lengthening the memory-forming stage of sleep actually reinforces epileptic seizures by "memorizing" the seizure pathways.

"Using brain devices that adjust stimulation based on both seizures and sleep patterns is an exciting possibility," Conrad said. Such devices use electrodes to record brain activity and deliver an electrical impulse to halt a seizure as soon as it’s detected. They use a closed-loop feedback system to improve detection over time as the system recognizes a specific person’s seizure patterns.

"This kind of approach could help test the study's main idea by seeing whether changing sleep-related brain activity after a seizure reduces the chance of future seizures," Conrad added. "If the theory holds up, these kinds of adaptive, closed-loop systems could become a new way to personalize treatment."

Kremen said the findings hint that electrical brain stimulation that interrupts this seizure memory formation could be an additional future treatment alongside medications for patients with drug-resistant epilepsy. "We are really invested in trying to find therapies for very sick people with epilepsy that don't have any hope with normal drug therapies," he said.

This article is for informational purposes only and is not meant to offer medical advice.

Engineers from MIT say that stacking circuit components on top of each other could be the answer to creating more energy-efficient artificial intelligence (AI) chips. The logic and memory components, which respectively perform computations and store data, can transfer data more easily when in direct contact as opposed to when apart.

The team created a so-called "memory transistor" comprising both a logic element that can perform computations (the transistor) and a memory element. This nanoscale device has relatively few electrical defects, meaning it can operate more quickly while using less electricity, the scientists said in two studies presented Dec. 9 and Dec. 10 at the International Electron Devices Meeting in San Francisco.

The breakthrough is particularly relevant for energy-intensive applications like AI, deep learning and computer vision. According to the International Energy Agency (IEA), global electricity consumption by data centers is projected to rise by about 130% to reach around 945 Terawatt-hours by 2030, largely due to a growing dependence on AI.

Just a single interaction with ChatGPT can generate enough heat that you need the equivalent of a bottle of water for cooling. But most of the energy associated with AI is used for shuttling data between components rather than performing computations. Even just a small saving on-chip could have a huge impact, the scientists believe.

"We have to minimize the amount of energy we use for AI and other data-centric computation in the future because it is simply not sustainable,” lead author of the study Yanjie Shao, a postdoctoral researcher at MIT, said in a statement. "We will need new technology like this integration platform to continue that progress."

Stacking saves energy — but it's not easy

Modern chips contain logic circuits made of transistors; these are on/off switches that control the flow of current. These transistors combine to represent binary 1s and 0s, which is how chips process information. They also have memory circuits, containing transistors alongside other materials that can store the data.

Logic and memory circuits are traditionally kept separate, and data must travel between them through wires and interconnects, wasting energy in the process. While stacking the active components may seem an obvious solution, the challenge lies in doing so without causing damage. Deposition, the controlled formation of ultrathin layers that form these components, needs to be done at low temperatures, for example, because some transistors cannot withstand heat.

To overcome this issue, the scientists built their logic transistor with an active channel layer (the region where electricity flows) made from indium oxide. Crucially, the material can be deposited in a two-nanometer layer at around 302 degrees Fahrenheit (150 degrees Celsius). This is a temperature low enough not to affect other transistors.

Beyond the indium oxide transistor, the scientists vertically stacked a memory component — a 10-nanometer layer of ferroelectric hafnium-zirconium-oxide — that allows the device to store data as well as process it. The resulting memory transistor can switch on or off in just 10 nanoseconds and operates at less than 1.8 volts. The switching speeds of typical ferroelectric memory transistors tend to be orders of magnitude lower, and require voltages between 3 and 4V.

The memory transistor is made even more efficient by being built on the chip’s "back-end," where the wires and metal bonds that connect the front-end’s active components are found. Shao said that doing this makes the integration density of the chip much higher.

For the two studies, the memory transistor was only installed on a chip-like structure rather than in a functional circuit. The team hopes to improve the transistor’s performance such that it can be integrated first into a single circuit, and then into larger electronic systems.

"Now, we can build a platform of versatile electronics on the back end of a chip that enable us to achieve high energy efficiency and many different functionalities in very small devices," Shao said. "We have a good device architecture and material to work with, but we need to keep innovating to uncover the ultimate performance limits."

You may assume that children have nightmares about monsters under the bed, while adults dream about stressful events like deadlines. But is there any scientific evidence showing that dreams change as we age?

Although there are plausible mechanisms for how aging could cause dreams to change over time, very little research has explored the topic.

"Dreaming depends on neural systems involved in imagination, memory and emotion, all of which develop and reorganize with age," Dr. Giulio Bernardi, head of the Sleep, Plasticity, and Conscious Experience (SPACE) research group at the IMT School for Advanced Studies Lucca in Italy, told Live Science. However, "surprisingly few studies have systematically examined how dreams change across the lifespan."

The studies that have investigated this idea have shown that people tend to report their dreams differently at various stages of their lives. While younger dreamers tend to see and feel more vividly, older people recall more complicated and less-emotional situations.

One of the simplest, and perhaps most common, explanations for the way our dreams adapt and evolve is called the "continuity hypothesis," first put forward in 1971.

According to that theory, our dreams tend to mirror what we're experiencing in our waking lives — if we're lounging on vacation, we may see sun and sand when we fall asleep, but if we're anxious about work, we may be transported to the office. But ultimately, the parallels between sleep and reality reveal very little about why our dreams might change as we grow up.

"Changes in dreaming across life reflect the complex interaction between brain development, sleep architecture, and cognitive-emotional maturation," Bernardi said. Everything from memory to sleep quality can influence how we experience both dreams and their aftermath: "These factors determine not only how vividly dreams are produced during sleep but also how likely they are to be remembered upon awakening."

How dreams change with age

The foundational research on how children dream was done by sleep researcher David Foulkes from the 1970s to the 1990s. According to his research, young people's dreams tend to be relatively straightforward — they feature animals, static objects and simple interactions. (However, research on children's dreams involves complications because the results depend on each child's ability to understand what dreams are and how to relay them to others.)

In adolescence, dreams tend to become more frequent and more vivid than they were in childhood, reflecting the many changes we're experiencing in our waking lives. While younger adolescents report dreaming about falling, being chased, and confronting monsters or animals, older teens reexperience the stresses of school and new relationships.

In adult life, dreams usually become a bit more mundane. One study found that adults and older adults dream about arriving somewhere late and "trying again and again to do something" more often than other age groups. Odd dreams and nightmares still occur, but the aggression of adolescence starts to fade and the complexity of dreams starts to reflect our waking life even more.

Studies show that in old age, people don't tend to report having as many dreams. Many also experience "white dreams," in which they recall having a dream but aren't quite sure what happened during it. While some of this can be explained by the lower quality of sleep that older adults tend to experience, much of this change — as is the case with dreams at all ages — has to do with the ability to accurately and descriptively remember what we saw in our sleep.

"Dreaming is defined as subjective experiences that occur during sleep," Michael Schredl, head of the sleep laboratory at the Central Institute of Mental Health in Germany, told Live Science. "What we get is only the dream or dream report, the recollection of those experiences that occurred during sleep."

At the end of life, and during the dying process, people often report seeing departed loved ones and recall visions of packing and preparing to go on a trip in their dreams. Studies of hospice patients have found that these dreams are often comforting and put people at ease, mirroring the reflection that often occurs at the end of life.

Sleep quiz: How much do you know about sleep and dreams?

Can we change bad memories? In this adapted excerpt from "How to Change a Memory" (Princeton University Press, 2025), author and neuroscientist Steve Ramirez recounts the events that led him and his colleagues to discover memories could be artificially controlled in rodents, by tapping directly into the brain.

Feelings like anxiety are hard to understand because they're often invisible to everyone else. But they're part of everyday life. We all regularly experience bouts of stress and anxiety. What if the job interviewer doesn't like me? Should I cram tonight for my exam tomorrow? What should I say on my first date?

Our biology often forces us to be prepared for multiple outcomes in the midst of uncertainty. It's healthy to care about these multiple outcomes because it encourages us to put in the work, to adequately prep for a given stressful event. And yet, sometimes the scales of stress become tilted to such an extreme that pathologies of the brain begin to emerge.

The tremendous variation in how any individual arrives at a state of anxiety, for example, highlights that our brain contains many winding roads that can ultimately converge on the same feeling. We all have our triggers in life, but what those triggers are depends on experience — on memory. When these differences impair our mood, thinking, behavior and overall daily functioning, then they get lumped into a category. What's more, if observed impairments share similar features, then this category itself falls within a broader classification — that of a mental disorder.

As I was entering my last year of graduate school, I was just beginning to understand how omnipresent an anxious feeling can truly be. Just as my own stressors in life began accumulating — finishing my thesis, writing grants and job applications, continuing the seemingly never-ending search for purpose as a scientist and person — my mom too had a sudden resurgence of anxious moments that ultimately culminated in frequent panic attacks. Once I learned about her lifelong experience with the erratic thing that anxiety was for her, I started to appreciate the on-again, off-again and on-again nature of these feelings. I couldn’t stop thinking about her panic attacks and how frustrating it was to not be able to press "off" on some of the most debilitating moments one can endure.

My last project in graduate school would attempt to artificially activate positive memories to suppress the symptoms associated with anxiety and depression. It would be my most personal scientific endeavor, a very direct way for me to join the fight at my mom's side and to thank her for being my superhero. If my research could somehow inspire new therapeutic strategies that might be useful for alleviating these kinds of debilitating conditions, then my work will have gained an even deeper, more personally meaningful purpose.

My lab partner Xu Liu and I wanted to take a brain-centric approach to our newest project. Could memory itself be artificially controlled in rodents, by tapping directly into the brain to restore neuronal and behavioral balance in a therapeutic name?

Luckily, our project had a scientific precedent in humans — in an influential paper by psychologist Barbara Fredrickson and colleagues called "The undoing effect of positive emotions." This study highlighted the capacity of positive emotions to undo the physiological effects that negative emotions have on the brain and body.

The undoing hypothesis proposes that positive emotions can be used for more than just feeling good. They can be used to help us get out of bed in the morning; pursue happiness; change how we think about and interact with ourselves and others; and counteract, or at least regulate, negative emotions. When human subjects were stressed and then watched movie clips that elicited contentment and amusement, their bodies rebounded in beneficial ways: their stress-induced increases in cardiovascular activity, for instance, returned to baseline faster than when they watched neutral or sad movie clips. Excitingly, this reveals a very real physical connection between feelings of positivity and their direct effects on our biology.

Xu and I wanted to further this work by testing for a potential therapeutic capacity of positive memories by jump-starting their biology from within the brain. We placed our animals in a box that had two small valves on separate ends: one that delivered sugar water when the animals licked it and another that delivered regular water. This is known as the sucrose preference test. Rodents normally prefer sugar water over regular water, the same way humans will typically find sugary liquids preferable to a bland liquid. On the other hand, rodents with depression-and anxiety-related behaviors tend to show a 50:50 preference. They show no preference at all.

As expected, the animals displaying anxiety-and depression-related behavior licked at each of the valves randomly over the course of 15 minutes. As with Project X — our first successful attempt at MIT to artificially control memories in the rodent brain — all we had to do was hit a button that would turn our lasers on and optogenetically awaken a memory from within.

Click.

The deep-blue laser flickered throughout the mouse’s hippocampus, waking up — activating — cells that held onto a positive memory. I remember thinking that our optogenetic stimulation was a fancy, high-tech Proustian madeleine, one capable of triggering the rich remembrance of things past. If you'll entertain my romanticization of the moment: the mouse perked up immediately, as if a shudder ran from its brain to its body, and it began scanning the environment to decide which valve to visit first.

An extraordinary thing was happening. I imagine that the mouse felt the memory invade all its senses, strangely detached and with no suggestion of an origin, since the essence of these sensations was in the mouse as much as it was the mouse. And once the positive memory fully revealed itself within seconds, the now-motivated mouse inspected each valve with some sniffing, followed by a taste test.

When it found the valve with the sugar water, the mouse started licking vigorously, so much so that it consumed as much sugar water as our control animals. In under an hour, Xu and I saw that reactivating positive memories restored our mice's behavior to a healthy baseline. Just as exciting, reactivating positive memories also turned on many areas of the brain involved in rewarding experiences and motivation.

The key to reversing abnormal behavior was embedded within their positive memories all along. For as long as the laser was shining its sapphire radiance in their brains, the mice were motivated to keep consuming their sugar water reward. All this from stimulating cells in the hippocampus. Or to say this with less novelistic flare: the mice got a sugary treat.

In the following weeks, one of my gifted undergraduates Briana Chen collected a large empirical dataset for the project, and it came with an exciting plot twist: when she artificially reactivated positive memories twice a day, or "chronically," for about a week, not only did this permanently ameliorate symptoms we believed were associated with depression and anxiety, but it also promoted the growth of new cells in the brain. Positive memories had both short- and long-term benefits, all the way from cells to behavior.

Inspired by the neuro-centric Research Domain Criteria (RDoC) approach to treating the brain, our hope was that the biological potency of positive memories — like medications — could inform cognitive-behavioral approaches to treating disorders of the brain. This project was meaningful to me on a personal level: I thought of my mom's panic attacks and the idea that she might never have to experience the kind of crippling anxiety that robs someone of peace.

Positive memories are some of the most powerful biological tools available in our brains. At home, my mom and I shared a treasure trove of them — one that we both remember is from the time when I was a teenager, and we were visiting her parents in El Salvador.

One morning, my cousins, parents and grandparents all walked down a hill behind the house my mom grew up in to go swimming in the village pond. My cousins kept egging me on to jump from a cliff into the pond, and my mom kept telling me I didn't have to.

Like her, I was the opposite of an adrenaline-seeker because, oh I don't know, maybe my innate biology was onto something, as "please do not free-fall to Earth" kept repeating in my mind. She could see that I was scared, and after a few minutes she suggested, much to my surprise, that we jump together. We held hands and tiptoed to the edge — uno, dos, tres — we were in the air! Moments later, we emerged from the water laughing in delightful disbelief at our newfound courage.

Neuroscience tells us that this memory has all the ingredients of life's dessert that make us feel good. From an RDoC perspective, my cognitive and valence systems are all interacting to produce the riches from this experience: the cognitive system enables the memory of jumping off of a cliff, which at first generated feelings of fear via the negative valence systems, which are now almost immediately counteracted by feelings of reward via the positive valence systems.

What was once a moment of fear is now a memory of triumph with my mom. It's the only time I can remember when we both took a literal leap of faith, so we cherish the memory as an example of what our brains can achieve together. A million little life moments like these, packaged neatly into a million memories that we hold onto constitute the good stuff in life.

Adapted from "How To Change a Memory: One Neuroscientist's Quest To Alter The Past". Copyright © 2025 by Steve Ramirez. Reprinted by permission of Princeton University Press.

We dream every night, but we often can't remember those dreams. Some mornings, we recall vivid details, and other days, we piece together hazy outlines. But what about color? Do most people dream in color or in black and white?

Some people may be surprised to learn that this has proved a divisive question. Modern research has indicated that television and films have a lot to do with how we experience dreaming and what we can remember when we wake up.

"Since we're used to colored media, we think dreams must be kind of like watching a movie or watching something on YouTube," Eric Schwitzgebel, a professor of philosophy at the University of California, Riverside, told Live Science. "Those things are colored, so we tend to assume that dreams are too."

But that hasn't always been the case. Up until the 1960s, researchers thought people largely dreamed in black and white, and surveys have backed this hypothesis. A small study of 277 people published in 1942 found that 70.7% of the college sophomores surveyed rarely or never saw colors in their dreams. Nearly 60 years later, Schwitzgebel asked a group of 124 college students the same questions — and the results had shifted drastically. In the more recent survey, less than 20% of the students surveyed reported rarely or never seeing colors in their dreams.

Other recent studies have produced similar results. Researchers have discovered a pattern: People born before the advent of color television and movies were much more likely to report having monochromatic dreams than people born after. This suggests that the way we interpret our dreams is affected by the types of media we consume.

Entertainment isn't the only factor. Much of what we take away from our nightly dreams has to do with how accurately we remember them and which details stick with us the most.

"Dreams are defined as subjective experiences during sleep, and the only way we can get to them is if the person is remembering them after waking up," Michael Schredl, head of the sleep laboratory at the Central Institute of Mental Health in Germany, told Live Science. "The main problem is, 'how good are you at recalling?'"

Just as in waking life, the colors of objects can be quite forgettable if they match what we expect to see. For example, a yellow banana in a dream probably wouldn't leave a lasting impression.

"You don't think about it, and it's difficult to remember," Schredl said. But if a neon-pink banana appears in a dream, it might make more of an impact.

What's more, if a particular color is significant to a person, they may be more likely to remember it.

"If the color has a specific meaning for the person in her or his waking life, then it might be that the color might point to something," Schredl said. "It's not about the color itself but how the color is affecting the person."

But Schwitzgebel argues that the question of whether we dream in black and white or color could be a bit misguided in the first place. When we imagine a scene in which the colors aren't important, our mental image may not be in black and white or in color; it may just be a fuzzy, "indeterminate" image. Or perhaps what we remember in the morning is slightly different from the mental image we had while dreaming, informed more by assumptions than memory. Dreams might be less of a visual, movie-like experience than we tend to assume, he said. Rather, it's possible our media consumption affects how we remember our dreams.

"A lot of people can't really quite get their minds around what it would mean for a dream experience to be neither colored nor black and white," he said.

Sleep quiz: How much do you know about sleep and dreams?

"Chemo brain" — chemotherapy-induced difficulties with focusing, thinking and remembering — may be caused by the cancer treatment's disruption to the brain's lymphatic system, an early-stage study suggests.

The study zoomed in on the meningeal lymphatics, the drainage network found in the protective tissue layer surrounding the brain. Dysfunction in this network has been linked to Alzheimer's disease, Parkinson's disease and traumatic brain injuries.

Now, the new research, published Oct. 13 in the journal Communications Biology, has linked damage to the meningeal lymphatics with the brain fog that patients commonly experience after receiving chemotherapy.

Using human and mouse cells, as well as living lab mice, researchers found evidence that a common type of chemotherapy drug that blocks cancer cells from dividing, called taxanes, damages the brain's lymphatic vessels and limits their drainage. Normally, the vessels would work together with the brain's glymphatic system to flush away metabolic waste.

"Lymphatic health really declined across all three models measured in different ways," study co-author Jennifer Munson, director of Virginia Tech's Cancer Research Center in Roanoke, Virginia, said in a statement. The vessels shrank and had fewer branches, which "are signs of reduced growth that indicate the lymphatics are changing, or not regenerating in beneficial ways," she said.

"Chemo brain" is a broad category of cognitive changes that follow chemotherapy and can last for years after treatment. "There's really a lot we don't know," Munson told Live Science, but these cognitive impairments have previously been linked to oxidative stress and inflammation, as well as impaired myelin production. (Myelin is fatty insulation that covers nerve fibers.)

"Others had looked on the neural side, so we wanted to focus on the meningeal side," Munson said.

To do this, Munson and her team used three models — human cells, mouse tissues and live mice — to assess whether chemotherapy drugs led to changes to the meningeal lymphatics at different scales.

First, they used cell lines to build a human-cell model of healthy meningeal lymphatics. This model paired cells from the lining of lymphatic vessels with meningeal cells. This enabled the team to tease apart the isolated effects of chemo on each cell's function. They also grew healthy mouse meningeal tissue in lab dishes to assess any structural changes triggered by the drug exposure.

They found that the drug docetaxel disrupted the cells in the human meningeal lymphatic model by reducing their coverage and length. The treatment also shrank the vessels within the mouse tissues and reduced the number of loops in the network structure.

Next, the researchers ran experiments with live mice, comparing mice treated with docetaxel to mice unexposed to the drug. Mice with cancerous tumors that were given the drug tended to have narrower meningeal lymphatic vessels, as well as fewer loops, compared to untreated mice.

The researchers wanted to see whether these docetaxel-induced structural changes led to impaired memory or changes in behavior. They found that healthy mice treated with docetaxel forgot objects they had previously seen, while the untreated mice showed clear signs of remembering them. MRI scans of the treated mice indicated that these cognitive issues correlated with the decreased flow of fluids through the lymphatic vessels, the authors wrote in the study.

Munson cautioned that this is an early-stage study and that there are many gaps left in our understanding of the link between "chemo brain" and meningeal lymphatics. She explained that one limitation of the research was that the chemotherapy drugs were administered over relatively short time periods, whereas chemotherapy courses for human cancer patients often last months.

Similarly, the memory issues the mice experienced were tested over a couple of days, whereas humans can sometimes experience chemo brain for years following treatment. "So it's possible that these lasting effects that we see in [human] patients may have different mechanisms that may not be captured fully here," Munson said.

It is important to replicate this research using samples from many individuals of different ages and to compare outcomes between tumor-bearing and tumor-free mice, to see if there's a difference in how the chemotherapy affects them, Munson said. She hopes that, eventually, this research will provide a new target for treating this side effect of chemotherapy.

"Ultimately, this work underscores the need to consider not only survival, but also the long-term, often overlooked neurological side effects of cancer treatment on cognitive well-being and quality of life," study co-author Monet Roberts, an assistant professor of biomedical engineering and mechanics at Virginia Tech, said in the statement.

This article is for informational purposes only and is not meant to offer medical advice.

Half-forgotten memories can be resurrected using "mental time travel," a new study suggests.

The research, published Monday (July 28) in the journal PNAS, showed that a person can rejuvenate their fading memories by recalling the emotions and thoughts they had when they first stored that memory. In fact, the researchers found that the refurbished memories were then almost as retrievable as newly formed memories.

The study specifically focused on memories of learned information, as opposed to memories of events, for instance. When we learn something, that new memory teeters on a forgetting curve, like a boulder perched atop a tall mountain. As that boulder rolls downhill, we lose some details of the memory. But as it approaches the base of the memory mountain, where the incline is less steep, the rate of forgetting slows down.

There are processes that "make the memories more and more stable and less sensitive to any type of forgetting processes," said study co-author Karl-Heinz Bäuml, a psychologist at the University of Regensburg in Germany. Some details remain etched into your memory, while others fade with time. But this forgetting might not be inevitable, Bäuml argued.

"You can reduce this type of forgetting if you mentally travel back in time to the context of encoding," meaning when you made the memory. In the new study, Bäuml and colleagues explored how this mental time travel affected memory retrieval.

The team recruited over 1,200 volunteers. Half were tasked with studying a short passage, while the other half studied lists of unrelated nouns. Each group was then split into four subgroups, which were asked to remember the material in different ways.

Related: Memories aren't static in the brain — they 'drift' over time

One group, which served as a point of comparison, was asked to recall the information they had just learned several times over the next hour, without performing any extra steps. The three other groups had a gap of four hours, 24 hours or seven days between learning the material and having their memories tested.

Upon being tested, these three groups were asked to mentally time travel, either by recalling the thoughts and feelings they had during their first session in the lab or by looking at a subset of the information they'd learned, as a kind of primer to remember the rest. The comparison group was also retested at these later time points, and their recall, sans time travel, was used as a benchmark.

Both types of mental time travel helped restore the participants' recollections, rolling their memories up the mountain to some degree. At the four-hour and 24-hour marks, these tricks improved recall by "reactivating" the memories. Remembering emotions from the earlier encoding restored about 70% of the targeted memories after four hours and 59% after 24 hours, while selective priming restored about 84% and 68% of the target memories at these time points.

However, after a week, the effect of mental time travel had waned. Remembering emotions didn't restore any memories, while priming restored only 31% of the target memories.

Deniz Vatansever, a cognitive neuroscientist at Fudan University in China who was not involved in the study, said the new work refines our understanding of memory. "Memory is not just linearly decaying, but actually we're able to reset it almost into its original form," he said. However, he said the real test would be to see how these findings generalize to life outside the lab.

"Autobiographical memories or other experiences that we have in daily life — they're rich in emotional content; they're rich in sensory modalities," he noted. By comparison, memories of short passages and word lists lack these features.

Bäuml agreed that the degree of memory rejuvenation will vary with factors not explored in the current study, such as the richness of the experiences being remembered. But for now, he said the evidence suggests that, if you're aiming to ace an exam, it might be best to schedule revision sessions with only short intervals in between.

"The best way would be to distribute your mental reinstatement a little bit and do it not only after seven days, but do it after three days, six days and so forth," he said. This would "create recurring rejuvenation cycles, which keep the memories all in all at a higher level," he suggested.

While this study found that single instances of mental time travel might nudge memories back up the mountain, other research has suggested that repeated practice might make it harder for the memory to roll down in the first place, said Justin Hulbert, a neuroscientist at Bates College who was not involved in the study.

This might mean that memories need to be refreshed regularly at first — after an hour or two — but that later refreshes could wait longer, maybe months or years, Hulbert said. "That might mean that you have to push the boulder up the mountain fewer times to still preserve that memory over long periods," he said.

Memories of places "drift" across the brain as they are carried by different sets of neurons over time, a new study in mice suggests.

Historically, neuroscientists thought that memories of locations and features of our immediate environment were encoded by specific "place cells." These place cells, located in a key memory center called the hippocampus, light up when a mammal enters the specific environment they correspond to — say, the door to a home or a waterfall on a hiking trail. It was thought that the activation of these place cells acted as a kind of map in the brain by encoding lasting memories of specific places as well as enabling navigation.

"Going back to the 1960s and 1970s, we basically thought that [spatial] memories were encoded by specific neurons in the brain," said senior study author Daniel Dombeck, a professor and principal investigator of neurobiology at Northwestern University. "That was the thought for probably 30, 40 years — until about 10 years ago."

In 2013, a paper in the journal Nature Neuroscience stirred some controversy and "blew everyone's mind," Dombeck said. The study employed newer techniques to probe cells in the mouse hippocampus, revealing that the brain's representation of places wasn't nearly as consistent as once thought. Some cells consistently reactivated when mice were returned to a maze again and again, but overall, the group of active neurons fluctuated. Rather than being a static "mental map," these spatial representations changed over the weeks-long experiment.

This phenomenon came to be known as "hippocampal representational drift," but the idea met some pushback. Some scientists wondered whether the shifts in brain activity were actually related to changes in the mice's environments — perhaps the smells or sounds in the maze differed between rounds of the experiment, or the rodents moved through the maze more slowly or quickly in a given round.

In their new study, published Wednesday (July 23) in the journal Nature, Dombeck and his team set out to control those unruly variables, and they did so using virtual reality and a tiny treadmill.

Related: Can your brain run out of memory?

In each round of the experiment, the mice were placed on a treadmill surrounded by screens. Akin to a video game controller, the treadmill acted as a conduit for the mice to explore a virtual maze, which was exactly the same every time. The team could then directly compare the trials where the mice ran the same speed, thus eliminating that variability.

Additionally, a cone was placed over each rodent's nose to pump in the same scent during every round, and white noise was played in the background to normalize the auditory landscape.

As the mice navigated the virtual maze, the researchers monitored the activity of their hippocampal cells in real time. They did this by opening a physical window into the brain and introducing a substance that glowed when brain cells were activated. They could then monitor this glow under a microscope. This setup doesn't limit the longevity of the lab mice, so they could run the experiment again and again over the course of the study, Dombeck noted.

By controlling the environment so tightly, "I was sure we were going to reduce this representational drift," he told Live Science. "I was sure that the memory was going to look more stable over days — and that's not what we found."

The team observed that only a small subset of cells — around 5% to 10% of those recorded — behaved like conventional place cells, lighting up consistently in each round. These stable cells were also the most excitable overall, meaning they were more likely to fire in response to a stimulus. In fact, the team could predict which cells were least likely to drift based on their level of excitability. Meanwhile, the less-excitable cells were much more prone to drift.

So why does this drift occur? "It might be a mechanism that the brain uses to separate highly similar experiences into discrete individual memories so that we could access them separately later," Dombeck suggested. So although you might return to a place repeatedly — work, school or a favorite park — you can nonetheless distinguish the different visits in your mind.

In other words, the drift may be a way for the brain to track the passage of time, he said.

Dombeck suspects this type of drift affects episodic memories, in general, which are about specific personal experiences that took place at particular locations and times. Other types of memory — such as motor memories, about learned movement skills — may be represented differently in the brain.

The study had a few limitations. For one, the brain-recording approach used in the study captured only a fraction of the cells in the mouse hippocampus — maybe 1% of its hundreds of thousands of neurons. But based on past studies, the team suspects similar processes are occurring across the hippocampus.

Additionally, research in mice isn't guaranteed to apply to humans. But Dombeck said he would expect the processes observed in this mouse study to be "fairly similar" to those unfolding in the human hippocampus. Because cells of the hippocampus become less excitable with age, it could be that memory worsens with age in part because those few stable cells at the core of our memories lose excitability, Dombeck suggested.

"If we could somehow tweak the excitability of our neurons or maintain that excitability over time, we could probably maintain memory," Dombeck speculated. But that idea will need to be backed up with further research.

You can use up all the storage on your phone or max out your computer's drive, but can you use up all the memory space in your brain?

Despite how you might feel before an exam or after a sleepless night before a work deadline, neuroscientists say that for a typical, healthy brain, memory capacity isn't fixed or easily used up.

"There isn't a meaningful limit to how much information the brain can store," said Elizabeth Kensinger, a professor of psychology and neuroscience at Boston College. "Memories can be thought of as the data the brain uses to understand the current moment, to make predictions about the future, and to scaffold future learning."

That's because the brain doesn't store memories as isolated files in one specific nerve cell. Instead, a single memory is distributed across many neurons called an engram — a group of brain cells connected and scattered across brain regions. Neuroscientists refer to this pattern, in which a memory is recorded across many neurons, as distributed representation. Each of those individual brain cells plays a role in many different memories.

Consider a memory, such as your 12th birthday party. It is not being stored in a single mental folder. The color of the balloons, the taste of the cake, the sound of your friends singing, and the feeling of excitement all activate different sensory and emotional centers — your visual cortex, taste cortex, auditory system and emotion-processing regions. These areas fire together in a specific pattern, and that pattern of neural activity stores the memory. When you recall that party later, you reactivate the pattern.

This method has significant advantages. Because neurons can participate in numerous combinations, the brain can encode huge numbers of memories. Kensinger suggests related memories share overlapping patterns, helping us to generalize and make predictions — something many neuroscientists believe is the reason for memory. And if a few neurons are damaged, the memory may still be recoverable because it's not stored in just one place.

Paul Reber, a professor of neuroscience at Northwestern University, explained to Live Science that distributed representation is part of what gives the brain its enormous memory capacity. The potential combinations grow exponentially, since each neuron participates in many memories involving overlapping neurons.

Why don't we remember everything?

If the brain isn't limited by memory space, why don't we remember everything? This is because the brain's memory system runs much more slowly than life happens. While information constantly streams in, only a fraction can make it into long-term storage.

Reber suggested thinking of memory like a video camera that only works at 10% of its capacity; we can only remember about a tenth of the specific events, experiences, and encounters we experience.

The information that does get into our memory system is gradually laid down into durable memories that will be there for the long term. That process is called consolidation.

"The storage process is the real bottleneck," Reber told Live Science, "not the total amount of space that you have."

What determines what we keep and what we forget?

At any given moment, tremendous amounts of information come into our brains from all our senses, but we don't need to remember it all.

Human memory did not evolve for perfect recall, Lila Davachi, a professor of psychology and neuroscience at Columbia University, noted. Our memory system evolved for survival, so we prioritize what is helpful so we can navigate the world.

"The memory system is built to only encode what is adaptive and necessary," Davachi, told Live Science.

"We just happened to get so good at it that we have this extra reserve that allows us to reminisce about things that happened when we were in college," Davachi said. "That's not adaptive. I'd argue we don't need it. Why is our memory system keeping that around? Well, it's possibly just an accident."

Kensinger explained that there are efficiencies in how the brain processes and remembers information. "When similar information is encountered over and over again," Kensinger said, "the brain tends to shift from storing the specific details to storing the more general content or schemas of the information. This is an efficient way to store information."

Consider your drive to school or to work. You don't remember every trip, because most of them are similar. Rather than storing each drive as its own memory, you recall the general experience. "The brain will tend to store the details of specific drives only if they had something distinctive happen, Kensinger added," perhaps a road was flooded, or you narrowly avoided an accident."

Far from running out of space, our brains constantly reshape what we know to help us adapt, predict and learn. So the next time you forget where you left your coffee cup, don't worry; you're not running out of space. It's likely your brain just had more important things to remember.

Psychology quiz: What do you know about psychology's most infamous experiments?

For decades, scientists believed neurons were the brain's sole architects of thought and memory — but now, new research suggests that another, often-overlooked type of brain cell may play a more central role in memory than previously thought.

The study, published in May in the journal PNAS, proposes that these other brain cells, called astrocytes, could be responsible for the brain's impressive memory-storage capacity through a newly discovered kind of network architecture.

Astrocytes are star-shaped cells that perform many maintenance tasks in the brain, including clearing cellular debris, supplying neurons with nutrients and regulating blood flow. They also sport thin branching structures, known as processes, that wrap around the points where neurons exchange messages. This wrapping forms what is called a tripartite synapse, a kind of three-way handshake involving the two connected neurons and the astrocyte.

"You can imagine an astrocyte as an octopus with millions of tentacles," said lead author Leo Kozachkov, who was a PhD student at MIT at the time the study was conducted and is now a postdoctoral fellow at IBM Research in Yorktown Heights, New York. "The head of the octopus is the cell body, and the tentacles are 'processes' that wrap around nearby synapses," Kozachkov told Live Science in an email.

Astrocytes don't transmit electrical impulses like neurons do. Instead, they communicate via calcium signaling, sending waves of charged calcium particles within and between cells. Studies have shown that astrocytes respond to synaptic activity by altering their internal calcium levels. These changes can then trigger the release of chemical messengers from the astrocyte into the synapse.

"These processes act as tiny calcium computers, sensing when information is sent through the synapse, passing that information to other processes, and then receiving feedback in return," Kozachkov said. Ultimately, this chain email gets back to the neurons, which adjust their activity in turn. However, researchers don't yet fully understand the precise computational functions astrocytes perform with the information they receive from neurons.

Related: The brain stores at least 3 copies of every memory

To better understand this function, Kozachkov and his colleagues turned to machine learning architectures that are capable of representing complex interactions between many actors, rather than capturing only simple connections between pairs of units.

Traditional machine learning networks that link only pairs of neurons might encode limited information, said senior study author Dmitry Krotov, a research staff member at the MIT-IBM Watson AI Lab and IBM Research. Because a single astrocyte could connect to thousands of synapses, the team hypothesized that astrocytes might mediate communication across all of these connections. That could explain how the brain achieves its massive storage capabilities, they proposed.

"The unique anatomical structure of astrocytes provides a very natural and tempting way to design these large information storage systems in biological hardware," Kozachkov told Live Science in an email.

The researchers also hypothesized that astrocytes store memories through gradual changes in their internal calcium patterns and that these patterns are then translated back into signals that get sent to neurons in the form of chemical messengers. In this model, each astrocyte process, rather than the whole cell, functions as a distinct computational unit, the team proposed.

"Our model does not need a lot of neurons to store a lot of memories," Kozachkov said. "This is a significant advantage from an energy efficiency perspective, since neurons are metabolically 'expensive.'"

The model offers a "biologically grounded explanation" for how these memory storage systems might operate in the brain, said Maurizio de Pittà, an assistant professor at the Krembil Research Institute in Toronto, Canada, who was not involved in the work. Past studies with high-resolution microscopes have supported this view, showing that astrocyte processes are interwoven throughout the brain and make contact with multiple synapses.

However, de Pittà told Live Science in an email that "models are powerful tools, but they remain approximations of the real world." He also cautioned that current technologies can not yet fully capture the dynamics unfolding in the human brain in real time, and that level of detail would be needed to validate the hypothesis.

Although scientists are starting to realize that astrocytes play a role in how we form memories, de Pittà said, we still don't have clear proof that the specific, calcium-based interactions between these cells and brain actually help create, store or recall memories, as suggested by the MIT team. If the team's model proves correct, though, the implications could offer a new way to think about brain storage, suggesting that memory capacity could scale with the number of astrocyte-synapse interactions present in the brain.

The model also offers potential therapeutic targets for neurodegenerative diseases, the study authors said.

"Astrocytes are known to be implicated in Alzheimer's and other memory disorders: our model provides a computational view of what might be going wrong," Kozachkov said. "Potentially, our mathematical model may inspire the search for new therapeutic targets: precise modulation of astrocyte process connectivity or signaling could restore or compensate for lost memory function."

However, much more research would be needed for this work to be translated into clinical treatments.

Beyond neuroscience, the model may point to applications in artificial intelligence. The model could help researchers create brain-like hardware systems, de Pittà said. Such systems could use dense memory architectures that enable them to store huge amounts of information and recall it efficiently, using very little energy, just like our brains do. This could be used for a wide array of applications, such as voice recognition; robotics and autonomous systems; AI assistants; or brain-machine interfaces and "neuroprosthetics."

Scientists in Japan have developed a new kind of "universal" computing memory that is much faster and less energy-hungry than modules used in the best laptops and PCs today.

Magnetoresistive Random Access Memory (MRAM) is a type of universal memory device that can overcome some of the limitations of conventional RAM, which can slow down at peak demand due to a relatively low capacity. Universal memory is a storage format that combines the speed of existing RAM and the ability of storage to retain information without a power supply

Universal memory like MRAM is a better proposition than the components used in computers and smart devices today as it offers higher speeds and much greater capacity, as well as better endurance.

This new technology operates at faster speeds and with greater capacity than conventional RAM, but overcomes the problem of high power requirements for data writing — which has previously been a challenge for MRAM.

MRAM devices consume little power in their standby state but need a large electric current to switch the direction of magnetization vector configurations of magnetic tunnel junctions, thereby using the direction of magnetization to represent the binary values in computers. That makes it infeasible for use in most computing systems and to achieve low-power data writing, a more efficient method for switching these vectors was needed.

Related: 'Quantum memory breakthrough' may lead to a quantum internet

In a paper published Dec. 25 2024 in the journal Advanced Science, researchers reported developing a new component for controlling the electric field in MRAM devices. Their method requires far less energy to switch polarity, thereby lowering the power requirements and improving the speed at which processes are performed.

Next-generation computing memory

The prototype component they built was called a "multiferroic heterostructure" — a ferromagnetic material and piezoelectric material, but with an ultrathin vanadium between them — that can be magnetized by an electric field. This differs from other MRAM devices, which did not have the vanadium layer.

Structural fluctuations in the ferromagnetic layer meant that it was difficult for a stable direction of magnetization to be maintained in previous MRAM devices. In order to overcome this stability issue, the Vanadium wafer between the ferromagnetic and piezoelectric layers acts as a buffer between the two.

By passing an electric current through the materials, the scientists demonstrated that the magnetic state could switch direction. The materials could maintain their shape and form, which previous versions could not do. Furthermore, the magnetic state was maintained after the electric charge was no longer present, allowing a stable binary state to be maintained without power.

The study did not cover the degradation in the switching efficiency over time. This tends to be a common problem with a wide range of electrical devices. For example, a common complaint with rechargeable household batteries is that they can only be charged a certain number of times (approximately 500) before their capacity degrades.

Ultimately, the new MRAM technology could enable more powerful commercial computing while also offering a longer use life, the scientists said. That's because the new switching technique requires far less power than previous solutions, has a greater resilience than current RAM technologies and does not require moving parts.

The X chromosome passed from mom to offspring may accelerate brain aging, a new animal study suggests.

The research highlights a potential fundamental difference in how males' and females' brains age. The research was conducted in mice, but if the findings translate to humans, they could point to sex-specific drivers of cognitive decline and, eventually, ways to prevent or treat them.

"Females show resilience in many measures of aging," said senior study author Dr. Dena Dubal, a professor of neurology and the David A. Coulter endowed chair in aging and neurodegenerative disease at the University of California, San Francisco (UCSF). For instance, they tend to live longer than males and have lower rates of various forms of dementia. One exception is Alzheimer's disease, which affects females at higher rates, but even so, some studies suggest that females survive longer with Alzheimer's than males do.

Dubal and colleagues wondered if the sex chromosomes, X and Y, could help explain these differences. There's evidence of genes on the X chromosome that help guard against dementia, while others contribute to the risk of cognitive decline, said Rachel Buckley, an associate professor of neurology at Harvard Medical School who was not involved in the new study.

The new study, published Jan. 22 in the journal Nature, uncovers a potential factor that shapes the X chromosome's influence.

Related: Is there really a difference between male and female brains? Emerging science is revealing the answer.

The origin of the X matters

Typically, females carry two X chromosomes in each cell — one from their mom and one from their dad. But a cell needs only one X to be active, so the other is "silenced." This results in females carrying a mosaic of cells that have silenced either their paternal or maternal X chromosome. Meanwhile, males — who typically carry one X and one Y — only ever inherit their X from their mother, and it's active in every cell.

"That makes us wonder about female resilience and whether that diversity of the X chromosome, having Mom's and Dad's, might contribute to resilience," Dubal said.

To explore this idea, Dubal; Samira Abdulai-Saiku, a postdoctoral fellow at UCSF; and colleagues did experiments with female lab mice of different ages. Some experiments involved using a genetic trick to silence all of the paternal X chromosomes in certain mice, leaving only the mother's X active. These mice were compared with others that had a mix of maternal and paternal X's switched on.

"I actually really liked that approach," Buckley said. Comparing females to males would have introduced additional sex-related factors, like hormonal differences, Buckley told Live Science.

The team also ensured that the X chromosomes from each parent were genetically identical, Dubal noted. So any differences that emerged would be related to which parent passed them along, not to differences in the genes themselves, she explained. This also enabled the team to pinpoint differences in epigenetics — chemical tags that attach to DNA and control which genes can be switched on.

Young "Mom-X" mice were cognitively similar to other young mice, performing about the same in maze-based tests. But at older ages, they showed starker cognitive decline, especially in their spatial memory and working memory. "The assays showed a pretty striking effect," Dubal said.

The team wondered if these declines were related to changes in the hippocampus, a key memory center in the brain. To see, they looked at epigenetic markers on DNA from the hippocampi of young and old mice. Epigenetic tags change across the lifespan, with certain patterns correlating with "higher" biological ages — in other words, a more advanced degree of aging. At older chronological ages, the Mom-X mice showed a greater degree of biological aging in the hippocampus than did mice with both X's.

The scientists then sorted neurons from the hippocampus based on whether the mom's or dad's X was active, so they could look at which genes were switched on.

Three genes were silenced on the maternal X — Sash3, Tlr7 and Cysltr1 — but were very active on the paternal X. Using the gene-editing tool CRISPR, they investigated what would happen if they switched these genes back on in the brains of old mice with only maternal X's. In tests, these mice showed improvements in spatial learning and memory.

What does it mean for humans?

Interestingly, in humans, these three genes are involved in immune protection, but their exact roles in neurons aren't fully understood, Dubal said. Future work could further investigate what the genes do in neurons and in other types of brain cells. It's also unclear how or why the X chromosomes from different parents undergo different epigenetic changes, she added.

The team also wants to investigate what these findings might mean for males, who carry only maternal X chromosomes — and could, in theory, then have greater rates of brain aging. "One can imagine" that, the more active maternal X's a person carries, the more pronounced the impact on brain aging, Dubal speculated. But that remains to be confirmed.

And, of course, because the current study was conducted only in mice, future research should look at human brain tissue to check that the results carry over, Buckley said. "This is such highly unique and novel work … but that is a caveat."

In the long run, this line of research could help scientists understand the influence of sex on dementia risk, differentiating it from other factors, like education, that are more closely tied to gender, Buckley said. By pinpointing those biological drivers of brain aging, researchers could better determine how to intervene and tailor treatments to individual patients.

"Right now, we're doing one size fits all," Buckley said. "And realistically, this is not how we're going to move the needle."

Over the past 12 months, we have seen significant strides in various areas of technology, ranging from electric vehicles to mixed-reality technologies, but much of the conversation has been dominated by artificial intelligence (AI).

While large language models — the current gold standard, which is based on neural networks that power everything from Windows Copilot to ChatGPT — have improved incrementally in 2024, this was the year that the existential risks of AI became disturbingly clear.

Another area poised for dramatic transformation is quantum computing, where new breakthroughs were reported every month. Not only are machines getting bigger and more powerful, but they're also becoming more reliable, as scientists inch closer to machines that outperform the best supercomputers. Some of the biggest breakthroughs came in error correction, which is a key problem that needs to be solved before quantum computers can realize their potential.

And in the world of electronics, scientists edged closer to realizing a hypothetical component known as "universal memory," which, if achieved, will transform the devices we use daily.

Here are the most transformative tech developments of 2024.

We're closer to understanding the existential risks of AI

This year, AI companies released incrementally better large language models — including OpenAI's o1, the Evo genetic mutation prediction model and the ESM3 protein sequencing model. We also saw better AI training and processing methods, such as a new tool that speeds up image generation by up to eight times and an algorithm that can compress these models so they're small enough to run locally on your smartphone.

Related: Humanity faces a 'catastrophic' future if we don’t regulate AI, 'Godfather of AI' Yoshua Bengio says

But this was also the year that the existential threats associated with AI came into sharp focus. In January, a study showed that widely used safety training methods failed to remove malicious behavior in models that had been "poisoned," or engineered to display harmful or undesirable tendencies.

The study, described by its authors as "legitimately scary," found that in one case, a rogue AI learned to recognize the trigger for its malicious actions and thus tried to hide its antisocial behavior from its human handlers. They could see what the AI was really "thinking" the whole time, of course, but this wouldn't always be the case in the real world.

We're forging a viable path to useful quantum computers

It was a busy 12 months in quantum computing research. In January, quantum computing company QuEra created a new machine with 256 physical qubits and 10 "logical qubits" — collections of physical qubits tied together through quantum entanglement — that reduces errors by storing the same data in different places. At the time, this was the first machine with built-in quantum error correction. But teams worldwide are trying to reduce the error rate in qubits.

The marquee development in error correction was unveiled in December, when Google scientists announced that they had built a new generation of quantum processing units (QPUs) that achieved a significant milestone in error correction, where, as you scale up the number of qubits, you fix more errors than you introduce. This will lead to exponential error reductions as the number of entangled qubits increases.

The new 105-qubit Willow chip, which is a successor to Sycamore, managed to achieve a breathtaking result in benchmarking, solving a problem in five minutes that a supercomputer would have taken 10 septillion years to crack — that's a quadrillion times the age of the universe.

"Universal memory" is inching close to reality — this is what it means for the devices we use

While this year brought several innovative computer components — including a new type of data storage that can withstand extreme heat, as well as a DNA-infused computer chip — some of the biggest advancements came in the development of "universal memory." This is a type of component that will dramatically increase the speed of computing and reduce energy consumption.

All computers use two types of memory at once: short-term memory, like random access memory (RAM), and long-term storage, like solid-state drives (SSDs) or flash memory. RAM is incredibly fast but requires a constant power supply; all memory stored in RAM is deleted as soon as a computer is turned off. SSDs, by contrast, are relatively slow but can retain information without power.

Universal memory is a third type of memory that combines the best of the first two kinds — and, in 2024, scientists inched closer to realizing this technology.

At the start of the year, scientists showed that a new material dubbed "GST467" was a viable candidate for phase-change memory — a type of memory that creates 1s and 0s of computing data when it switches between high- and low-resistance states in a glass-like material. When it crystallizes, it represents 1 and releases a large amount of energy. When it melts, it represents 0 and absorbs the same amount of energy. In testing, this material proved faster and more efficient than other candidates for universal memory, such as ULTRARAM, the current leading candidate.

Other candidates are also promising — and bizarre. In April, for example, scientists proposed that a weird magnetic quasiparticle known as a "skyrmion" may one day be used in universal memory instead of electrons. In the new study, they sped up skyrmions from their normal speeds of 100 meters per second (roughly 225 mph, or 362 km/h) — which is too slow to be used in computing memory — to 2,000 mph (3,200 km/h).

Then, toward the end of the year, scientists accidentally discovered another material that could be used for phase-change memory. This one lowered the energy requirements for data storage by up to a billion times. This discovery happened entirely by chance, showing that, in the world of science and technology, you may never know how close you are to a major breakthrough.

Intense stress can lead to fuzzy memories, which can lead to more generalized fear responses. Now, scientists may have just discovered why.

A study in mice, published Friday (Nov. 15) in the journal Cell, suggests that stress hormones can distort how memories are recorded, leading to less-precise recollections and a future tendency to be unable to properly distinguish between safe triggers and threats.

The new findings could help uncover new avenues to treat people with post-traumatic stress disorder (PTSD) and generalized anxiety disorder.

"This is a tour de force study answering an age-old question that has not been answered — How does a traumatic or highly stressful experience increase fear generalization?" Denise Cai, an associate professor of neuroscience at the Icahn School of Medicine at Mount Sinai who wasn't involved in the study, told Live Science in an email.

Scientists have long known that acute stress changes how memories are encoded, said study lead author Sheena Josselyn, a memory researcher at The Hospital for Sick Children and the University of Toronto.

For example, a person exposed to gunfire might later feel intense fear after a loud noise, which is an inappropriate response. This is called fear overgeneralization.

Josselyn and colleagues set out to understand what happens in the brain as these memories are formed.

They restricted lab mice's movements for 30 minutes — an acutely distressing experience for the rodents. The mice were then trained to recognize two specific noises — one that preceded an uncomfortable electric shock, and one that didn't. As expected, the stressed mice did not remember the noise well and instead became scared of many sounds.

A closer look at these mice's brains revealed that the stress affected the traumatic event's "engram," the physical trace of a memory left behind as a group of neurons changes to encode the memory.

A typical engram tends to be quite "sparse," using a small number of brain cells, Josselyn told Live Science. This ensures that recollections don't get muddled together, she said. After exposure to stress, however, the engrams became larger, the team found.

This is because strong stress blocked inhibitory interneurons, or cells that typically regulate how excitable other neurons are. These cells usually act as gatekeepers that limit how many neurons are looped into an engram, the study found.

"These are like the bouncers at the nightclub that keep out the riffraff: Only the most excitable neurons are allowed into this nightclub and become part of the engram," Josselyn said.

By triggering the release of corticosterone, the mouse equivalent of the human stress hormone cortisol, stress sparked the release of a neurotransmitter called endocannabinoid, which then blocked the action of the inhibitory interneurons.

The fact that more neurons are encoding a traumatic memory may explain both why these memories can be hazy and why people tend to overgeneralize fear from the original event to other experiences.

Importantly, administering metyrapone, a chemical that inhibits the synthesis of corticosterone, before the mice were exposed to the stress reversed that effect without altering the memory of the original stressful event.

Because the study was done on mice, it's not yet clear whether the results can be applied to humans, Josselyn said.

Still, by providing insights into how stress can lead to the overgeneralization of memory, the study could help researchers develop targeted treatments to counteract the effect without affecting other memories, Cai said.

"This has a lot of translational relevance for mental health disorders, such as PTSD and generalized anxiety disorder," she said.

The study also raises questions about the use of cannabis in the context of PTSD, Josselyn said.

A few clinical trials are studying whether cannabinoids or cannabis products could treat PTSD and other anxiety disorders, but the field is still in its infancy. As a result, the US Department of Veteran Affairs recommends against the use of cannabis products in the treatment of PTSD. Still, anecdotal reports suggest some people with PTSD have been using cannabis, possibly to self-medicate, Josselyn said.

"People are using a lot of cannabis for recreational and halfway-medicinal purposes. But the scary thing is that we really don't understand a lot of the effects of cannabinoids" in PTSD, she said. "That really means we absolutely need to study this."

Forgetting is part of our daily lives. You may walk into a room only to forget why you went in there — or perhaps someone says hi on the street and you can't remember their name.

But why do we forget things? Is it simply a sign of memory impairment, or are there benefits?

One of the earliest findings in this area highlighted that forgetting can occur simply because the average person's memories fade away. This comes from 19th century German psychologist Hermann Ebbinghaus, whose "forgetting curve" showed how most people forget the details of new information quite rapidly, but this tapers off over time. More recently, this has been replicated by neuroscientists.

Related: Why do we forget things we were just thinking about?

Forgetting can also serve functional purposes, however. Our brains are bombarded with information constantly. If we were to remember every detail, it would become increasingly difficult to retain the important information.

One of the ways that we avoid this is by not paying sufficient attention in the first place. Nobel prize winner Eric Kandel, and a host of subsequent research, suggest that memories are formed when the connections (synapses) between the cells in the brain (the neurons) are strengthened.

Paying attention to something can strengthen those connections and sustain that memory. This same mechanism enables us to forget all the irrelevant details that we encounter each day. So although people show increased signs of being distracted as they age, and memory-related disorders such as Alzheimer's disease are associated with attention impairments, we all need to be able to forget all the unimportant details in order to create memories.

Handling new information

Recalling a memory can sometimes also lead to it changing for the purposes of coping with new information. Suppose your daily commute involves driving the same route every day. You probably have a strong memory for this route, with the underlying brain connections strengthened by each journey.

But suppose one Monday, one of your usual roads is closed, and there's a new route for the next three weeks. Your memory for the journey needs to be flexible enough to incorporate this new information. One way in which the brain does this is by weakening some of the memory connections, while strengthening new additional connections to remember the new route.

Clearly, an inability to update our memories would have significant negative consequences. Consider PTSD (post-traumatic stress disorder), where an inability to update or forget a traumatic memory means an individual is perpetually triggered by reminders in their environment.

From an evolutionary standpoint, forgetting old memories in response to new information is undoubtedly beneficial. Our hunter-gatherer ancestors might have repeatedly visited a safe water hole, only to one day discover a rival settlement, or a bear with newborn cubs there. Their brains had to be able to update the memory to label this location as no longer safe. Failure to do so would have been a threat to their survival.

Reactivating memories

Sometimes, forgetting may not be due to memory loss, but to changes in our ability to access memories. Rodent research has demonstrated how forgotten memories can be remembered (or reactivated) by supporting the synaptic connections mentioned above.

Rodents were taught to associate something neutral (like a bell ringing) with something unpleasant (like a mild shock to the foot). After several repetitions, the rodents formed a "fear memory" where hearing the bell made them react as though they expected a shock. The researchers were able to isolate the neuronal connections which were activated by pairing the bell and the shock, in the part of the brain known as the amygdala.

They then wondered if artificially activating these neurons would make the rodents act as if they expected their foot to be shocked even if there was no bell and no shock. They did this using a technique called optogenetic stimulation, which involves using light and genetic engineering, and showed that it was indeed possible to activate (and subsequently inactivate) such memories.

One way that this might be relevant to humans is through a type of transient forgetting which might not be due to memory loss. Return to the earlier example where you see someone in the street and can't remember their name. Perhaps you believe you know the first letter, and you'll get the name in a moment. This is known as the tip-of-the-tongue phenomenon.

When this was originally studied by American psychologists Roger Brown and David McNeill in the 1960s, they reported that people's ability to identify aspects of the missing word was better than chance. This suggested that the information was not fully forgotten.

One theory is that the phenomenon occurs as a result of weakened connections in memory between the words and their meanings, reflecting difficulty in remembering the desired information.

However, another possibility is that the phenomenon might serve as a signal to the individual that the information is not forgotten, only currently inaccessible.

This might explain why it occurs more frequently as people age and become more knowledgeable, meaning their brains have to sort through more information to remember something. The tip of the tongue phenomenon might be their brain's means of letting them know that the desired information is not forgotten, and that perseverance may lead to successful remembering.

In sum, we may forget information for a host of reasons. Because we weren't paying attention or because information decays over time. We may forget in order to update memories. And sometimes forgotten information is not permanently lost, but rather inaccessible. All these forms of forgetting help our brain to function efficiently, and have supported our survival over many generations.

This is certainly not to minimise the negative outcomes caused by people becoming very forgetful (for example, through Alzheimer's disease). Nonetheless, forgetting has its evolutionary advantages. We only hope that you've found this article sufficiently interesting that you won't forget its contents in a hurry.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Researchers have developed a new type of memory cell that can both store information and do high-speed, high-efficiency calculations.

The memory cell enables users to run high-speed computations inside the memory array, researchers reported Oct. 23 in the journal Nature Photonics. The faster processing speeds and low energy consumption could help scale up data centers for artificial intelligence (AI) systems.

"There's a lot of power and a lot of energy being put into scaling up data centers or computing farms that have thousands of GPUs [graphics processing units] that are running simultaneously," study co-author Nathan Youngblood, an electrical and computer engineer at the University of Pittsburgh, told Live Science. "And the solution hasn't necessarily been to make things more efficient. It's just been to buy more and more GPUs and spend more and more power. So if optics can address some of the same problems and do it more efficiently and faster, that would hopefully result in reduced power consumption and higher throughput machine learning systems."

The new cell uses magnetic fields to direct an incoming light signal either clockwise or counterclockwise through a ring-shaped resonator, a component that intensifies light of certain wavelengths, and into one of two output ports. Depending on the intensity of light at each of the output ports, the memory cell can encode a number between zero and one, or between zero and minus one. Unlike traditional memory cells, which only encode values of zero or one in one bit of information, the new cell can encode several non-integer values, allowing it to store up to 3.5 bits per cell.

Related: New 'petabit-scale' optical disc can store as much information as 15,000 DVDs

Those counterclockwise and clockwise light signals are akin to " two runners on a track that are running in opposite directions around the track, and the wind is always in the face of one and to the back of the other. One can go faster than the other," Youngblood said.. "You're comparing the speed at which those two runners are running around the track, and that allows you to basically code both positive and negative numbers."

The numbers that result from this race around the ring resonator could be used to either strengthen or weaken connections between nodes in artificial neural networks, which are machine learning algorithms that process data in ways similar to the human brain. That could help the neural network identify objects in an image, for example, Youngblood said.

Unlike traditional computers, which make calculations in a central processing unit then send results to memory, the new memory cells perform high-speed computations inside the memory array itself. In-memory computing is particularly useful for applications like artificial intelligence that need to process a lot of data very quickly, Youngblood said.

The researchers also demonstrated the endurance of the magneto-optic cells. They ran more than 2 billion write and erase cycles on the cells without observing any degradation in performance, which is a 1,000-fold improvement over past photonic memory technologies, the researchers wrote.Typical flash drives are limited to between 10,000 and 100,000 write and erase cycles, Youngblood said.

In the future, Youngblood and his colleagues hope to put multiple cells onto a computer chip and try more advanced computations.

Eventually, this technology could help mitigate the amount of power needed to run artificial intelligence systems, Youngblood said.

New brain scans may help unravel a fundamental mystery about how our memory works on a day-to-day basis.

Similar to how a movie is divided into scenes, our brains organize our memories of each day into segments — separating when we went out to lunch from when we came home from work, for instance. But in movies, directors and editors decide when one scene ends and a new one begins. So how does the brain choose?

In theory, shifts in our environment may dictate when we've "entered a new scene," or instead, the brain may somehow determine the boundary between scenes.

Now, in a paper published Oct. 3 in the journal Current Biology, researchers found that the latter theory is likely correct — and that we may have more control over how we interpret the day's events than scientists previously thought.

Related: Sherlock Holmes' famous memory trick really works

Senior study author Christopher Baldassano, an associate professor of psychology at Columbia University, and his team wanted to understand what leads the brain to form boundaries around daily events, essentially changing from one "scene" to another. The leading theory has been that these boundaries are raised by a major change in the environment, such as when you walk into a movie theater or enter a grocery store, going from outside to inside.

However, another hypothesis suggests that these boundaries are created by our own past experiences and feelings about certain events or environments. So, while a change in environment can affect the segmentation of someone's day, it's possible that this influence can be overridden by our own priorities and goals.

To explore these hypotheses, Baldassano and his team created 16 short audio narratives. Each narrative involved four locations: a restaurant, a lecture hall, a grocery store and a restaurant. They also included four social situations: a business deal, a "meet-cute," a proposal and a breakup.

Volunteers listened to these narratives like podcasts while the scientists used functional magnetic resonance imaging (fMRI) to scan the participants' brains. Using a special method that the team had developed previously, they tracked changes in brain activity, especially in the medial prefrontal cortex (mPFC), part of the brain that perceives and interprets moment-to-moment input from our surroundings.

"We now had a tool where we could figure out what these dynamics look like and how people are dividing up these experiences," Baldassano told Live Science. They were able to track when a participant formed a new boundary during the narrative.

mPFC activity spiked when the key social events in the storyline changed — when the business deal was closed or the marriage proposal was accepted. However, if the team told participants to focus on features of the locations instead — such as sitting down at a restaurant and ordering food — their segmentation of the events changed, as did their brain activity.

The study also revealed differences in how the volunteers remembered the narratives after hearing them. When the participants were asked to recall the part of the story they were not asked to pay attention to, they forgot many details.

Related: The brain stores at least 3 copies of every memory

"You could view that as a good or a bad thing, in the sense that depending on the frame of mind you go into things with, it really does change your memory of what actually happened," Baldassano said.

Overall, though, "these results are exciting because they reveal how flexible and active our memory can be," said David Clewett, an assistant professor of cognitive psychology at UCLA who was not involved in the study. "Instead, we can choose what we pay attention to and what we remember. This means that, in many ways, we control the narrative of our own experiences," Clewett told Live Science in an email.

Difficulties with event segmentation is also common with certain conditions, such as post-traumatic stress disorder and dementia, as well as in normal aging.

The study suggests "memory-based treatments shouldn't just focus on any shift in a narrative to improve long-term memory," Clewett said. "Attention should be directed toward key moments — those that truly capture the essence and structure of an experience — to help people better understand and remember what matters most."

The researchers now hope to probe how long-term memory is affected by consciously shifting your attention as you divide the day into scenes.

"If you allow people to freely respond about what they remember," Baldassano wondered, "to what extent does this [shift in focus] change the way that they either frame the story or the kind of details they include?"

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Have you ever walked into a room and forgotten why you went in there, or been about to speak but suddenly realized you had no idea what you were going to say? The human brain normally balances countless inputs, thoughts and actions, but sometimes, it seems to short-circuit. So what really happens when we forget what we were just thinking about?

Understanding why we forget first requires an understanding of how our memory works — and dispelling some myths about memory.

"Memory is not just one thing," Susanne Jaeggi, a professor of psychology at Northeastern University, told Live Science. "There are very different components of memory, and they're also related to different cognitive processes."

In this case, it's important to know two different types of memory: long-term and working memory. Long-term memories are a broad, multifaceted category of memories that involve knowledge, experiences and skills stored in the brain for extended periods — from hours up to an entire lifetime. On the other hand, thoughts in working memory dash through the mind for only seconds or minutes at a time.

Related: 'Short-term memory illusions' can warp human recollections just seconds after events, study suggests

Working memory is like the "sketchpad of conscious thought," Earl K. Miller, a professor of neuroscience at MIT, told Live Science. Every tidbit of new information, inner dialogue and sensory input routes through working memory, and certain characteristics of working memory likely explain why we forget those thoughts.

First, working memory has very limited capacity. There's been some debate over exactly what the limit is and how to test for it, but psychologists estimate that people can hold only about four to seven "chunks" of information — such as letters, digits, words or phrases — in their working memory at a time. Rather than being aware of all of these "chunks" simultaneously, the brain bounces around from one idea to another, making it more likely that one gets lost in the shuffle, Miller explained.

Second, the brain quickly erases unimportant things from working memory to make room for new information. So unless those short-term memories are transferred into long-term memories (a process called consolidation), they're soon gone from conscious thought.

Because the brain isn't actually capable of multitasking, Miller said, it has to "juggle" different thoughts as our working memory darts around to different ideas. That requires conscious effort and attention, which are overseen by the brain's prefrontal cortex, a region involved with complex learning, decision making and reasoning. If attention becomes focused on only one of those thoughts or is diverted somewhere new, the brain loses track of the earlier thoughts.

"It drops one of the 'balls,' and that's why you forget stuff," Miller said.

The brain is especially likely to "drop the ball" from working memory when it's sleepy or impaired by alcohol or other drugs. Age is also a factor; Miller said working memory function peaks in a person's 20s and starts to decline during middle age.

But for those who regularly struggle with thoughts slipping their mind, Jaeggi and Miller have some evidence-based advice.

To stop forgetting so many things in the first place, Miller advised against multitasking. "When you think you're multitasking, what you're doing instead is, you're juggling," he said, and juggling makes forgetting more likely.

Jaeggi gave a tip for what to do when a thought is already gone.

"Recreating the context can help," she said. That means going back into the room you were before, or retracing your thoughts. Those context clues might give the brain the extra boost it needs to reach back a few seconds in working memory and retrieve the thought before it's gone entirely.

Memories evolve throughout our lifetimes, changing as we learn and experience new things and as we recall a memory repeatedly. And then, memories degrade as we age.

Previously, scientists thought that this malleability was the result of changes in the brain cells that originally encoded the memory, and they believed these cells stored just one copy of every memory in the brain. However, new research suggests that might not be true.

The scientists found that, in rodents, the brain stores at least three copies of a given memory, encoding it in multiple places in the organ.

These copies are encoded by different groups of neurons in the hippocampus, a brain region critical for learning and memory. The copies vary in terms of when they're created, how long they last and how modifiable they are through time.

Related: How accurate are our first childhood memories?

In the new study, published Aug. 16 in the journal Science, the scientists showed that, as mice encode new memories, they first create so-called early-born neurons. These neurons are responsible for storing a long-term copy of the memory that is initially weak but becomes stronger over time.

Next comes middle-ground neurons, which are more stable from the outset, followed by late-born neurons that from the beginning encode very strong copies of a memory. However, that strength fades over time.

Researchers uncovered these findings by examining the activity of different groups of neurons in the hippocampus after mice had completed various memory tasks. These tasks involved learning to avoid harmful situations, such as receiving an electric shock to their feet, before being confronted with the same task later on.

The way these three groups of neurons operate on different timescales may help explain how the brain regulates memories over time, the study authors suggested. However, it is still unclear how exactly these neurons interact with each other to facilitate this, study co-author Flavio Donato, an assistant professor of neurobiology at the University of Basel in Switzerland, told Live Science.

Notably, the memories stored by late-born neurons were more plastic, or malleable, than those of early-born neurons, the team found. This suggests that at the start of memory formation — when early-born neurons reign — the information stored remains fairly stable over time, while memories stored later on are more easily warped by new information.

If the same phenomenon happens in humans, this finding could someday lead to the development of new therapies for specific disorders, Donato said. For example, in post-traumatic stress disorder (PTSD), people experience intrusive memories, meaning unwanted, distressing memories of a traumatic event. Perhaps a drug could be designed that preferentially activates late-born neurons, which are more plastic and thus more receptive to psychotherapy, he said.

In the case of people with memory loss due to dementia, meanwhile, another type of drug could stimulate the activity of early-born neurons, whose data is stored more rigidly. Broadly speaking, such treatments would manipulate the properties of a memory by selecting which type of neuron is used to encode it in the brain, Donato explained.

"I feel like we now have biological entry points to modulate the plasticity of memory in a way that might allow us to push it towards being more or less plastic, in order to preserve it or to basically re-write it," Donato said.

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Some memories last a lifetime — and now, scientists have revealed a type of molecular "glue" that helps those memories stick around. 

Memories form when collections of neurons in a region of the brain called the hippocampus activate in response to a particular experience. Each time you recall that experience, the same set of cells activates. When one neuron repeatedly activates another, the connection between those neurons strengthens. 

Over time, this process in the hippocampus, along with related activity in other regions of the brain, solidifies a short-term memory into a long-term one. 

To maintain these long-term memories, brain cells make proteins that help strengthen the connections, or synapses, between neurons. One critical protein is the enzyme PKMzeta, which is continually made by neurons. However, an outstanding question is how this enzyme "knows" to go to the right synapses to ensure that certain memories stay with us forever. 

In a new study, scientists think they've found the answer: an unsung molecule called KIBRA glues the enzyme to strong synapses and also summons new PKMzeta to replace that enzyme when it degrades. The researchers published their findings Wednesday (June 26) in the journal Science Advances. 

Related: The brain has a 'tell' for when it's recalling a false memory, study suggests

Previous research in humans suggested that different versions of the KIBRA molecule are associated with differences in memory performance, either better or worse. KIBRA was also already known to interact with the PKMzeta enzyme in the hippocampus of mice. So, the scientists behind the new study decided to delve further into that interaction. 

In lab experiments, the team investigated whether blocking the interaction between KIBRA and PKMzeta influenced how well mice performed in long-term memory tests. These tests included seeing whether the mice could remember to avoid entering an area where they had previously been shocked with electricity. 

Blocking the interaction between KIBRA and PKMzeta impaired the mice's long-term spatial memory — in other words, their ability to avoid the shock zone. 

In a separate experiment, when the KIBRA-PKMzeta interaction was left undisturbed, the team found that even when PKMzeta degraded as expected, new complexes of KIBRA and PKMzeta formed in the hippocampus. This, in turn, helped maintain the mice's memory of the shock zone for a month. 

Earlier work by the same team showed that if researchers increase the amount of PKMzeta in a rodent's brain, it appears to enhance weak long-term memories that have faded over time. This initially surprised the scientists, as the team expected PKMzeta to boost the strength of synapses at random, rather than specifically acting on those involved in long-term memory. 

Instead, the new findings suggest that KIBRA acts like a "glue," sticking to these strong synapses and also guiding PKMzeta to them, which would explain this phenomenon, the team said. 

The research is only in its infancy. However, eventually, it may be possible to someday use this knowledge to treat brain disorders that cause memory loss, such as Alzheimer's disease, said study co-senior author André Fenton, a professor of neural science at New York University. Such treatments could work by using KIBRA to  deliver PKMzeta or similar molecules to weakened synapses. 

However, with neurodegenerative diseases such as Alzheimer's, the conditions damage and eventually kill off neurons in the brain. That means that this kind of therapy would theoretically only work for as long as there are still synapses left to enhance. 

For now, more research is needed to understand how the interaction between PKMzeta and KIBRA actually translates into people's experiences of memory. 

"We have quite a way to go to turn the description of these molecules into that experiential thing that we cherish — what we call memory, belief, intention and so forth," Fenton said. 

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The brain may be able to hold nearly 10 times more information than previously thought, a new study confirms.

Similar to computers, the brain's memory storage is measured in "bits," and the number of bits it can hold rests on the connections between its neurons, known as synapses. Historically, scientists thought synapses came in a fairly limited number of sizes and strengths, and this in turn limited the brain's storage capacity. However, this theory has been challenged in recent years — and the new study further backs the idea that the brain can hold about 10-fold more than once thought.    

In the new study, researchers developed a highly precise method to assess the strength of connections between neurons in part of a rat's brain. These synapses form the basis of learning and memory, as brain cells communicate at these points and thus store and share information. 

By better understanding how synapses strengthen and weaken, and by how much, the scientists more precisely quantified how much information these connections can store. The analysis, published April 23 in the journal Neural Computation, demonstrates how this new method could not only increase our understanding of learning but also of aging and diseases that erode connections in the brain.. 

Related: The brain has a 'tell' for when it's recalling a false memory, study suggests

"These approaches get at the heart of the information processing capacity of neural circuits," Jai Yu, an assistant professor of neurophysiology at the University of Chicago who was not involved in the research, told Live Science in an email. "Being able to estimate how much information can potentially be represented is an important step towards understanding the capacity of the brain to perform complex computations."

In the human brain, there are more than 100 trillion synapses between neurons. Chemical messengers are launched across these synapses, facilitating the transfer of information across the brain. As we learn, the transfer of information through specific synapses increases. This "strengthening" of synapses enables us to retain the new information. In general, synapses strengthen or weaken in response to how active their constituent neurons are — a phenomenon called synaptic plasticity. 

However, as we age or develop neurological diseases, such as Alzheimer's, our synapses become less active and thus weaken, reducing cognitive performance and our ability to store and retrieve memories. 

Scientists can measure the strength of synapses by looking at their physical characteristics. Additionally, messages sent by one neuron will sometimes activate a pair of synapses, and scientists can use these pairs to study the precision of synaptic plasticity. In other words, given the same message, does each synapse in the pair strengthen or weaken in exactly the same way? 

Measuring the precision of synaptic plasticity has proven difficult in the past, as has measuring how much information any given synapse can store. The new study changes that. 

To measure synaptic strength and plasticity, the team harnessed information theory, a mathematical way of understanding how information is transmitted through a system. This approach also enables scientists to quantify how much information can be transmitted across synapses, while also taking account of  the "background noise" of the brain. 

This transmitted information is measured in bits, such that a synapse with a higher number of bits can store more information than one with fewer bits, Terrence Sejnowski, co-senior study author and head of the Computational Neurobiology Laboratory at The Salk Institute for Biological Studies, told Live Science in an email. One bit corresponds to a synapse sending transmissions at two strengths, while two bits allows for four strengths, and so on.

The team analyzed pairs of synapses from a rat hippocampus, a region of the brain that plays a major role in learning and memory formation. These synapse pairs were neighbors and they activated in response to the same type and amount of brain signals. The team determined that, given the same input, these pairs strengthened or weakened by exactly the same amount — suggesting the brain is highly precise when adjusting a given synapse's strength.

The analysis suggested that synapses in the hippocampus can store between 4.1 and 4.6 bits of information. The researchers had reached a similar conclusion in an earlier study of the rat brain, but at that time, they'd crunched the data with a less-precise method. The new study helps confirm what many neuroscientists now assume — that synapses carry much more than one bit each, Kevin Fox, a professor of neuroscience at Cardiff University in the U.K. who was not involved in the research, told Live Science in an email.    

The findings are based on a very small area of the rat hippocampus, so it's unclear how they'd scale to a whole rat or human brain. It would be interesting to determine how this capacity for information storage varies across the brain and between species, Yu said. 

In the future, the team's method could also be used to compare the storage capacity of different areas of the brain, Fox said. It could also be used to study a single area of the brain when it's healthy and when it's in a diseased state. 

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Scientists have discovered a new mechanism in which a concentrated laser beam can change the magnetic state of a solid material. The finding could one day be harnessed in ultrafast computing memory, the researchers say.

The scientists formulated a new equation that describes the link between the amplitude of the magnetic field of light, its frequency and the energy absorption properties of a magnetic material. The scientists published their findings in a study on Jan. 3 in the journal Physical Review Research.

The equation is "completely new and also very elemental," study co-author Amir Capua, a physics professor at Hebrew University of Jerusalem, told Live Science.

Although the discovery builds on the field known as "magneto-optics," this represents a new paradigm because scientists didn't previously understand that the magnetic component of a rapidly oscillating light wave can control magnets, he said. The equation describes the characteristics of this interaction.

Computer memory uses miniature electromagnets that are magnetized with voltage to enable the binary states of "on" or "off" to encode data, which are read and reinterpreted by a processor as 1 or 0. 

The most common computing memory, like those found in laptops or phones, comes in the form of dynamic random access memory (DRAM). This is volatile, meaning when power is switched off, all data held is lost, but it's easier to engineer, uses common materials and has low error rates — and those few errors are easy to detect and fix.

The new finding is more relevant for a technology called magnetoresistive random access memory (MRAM), which is a non-volatile memory more commonly used in spacecraft as well as military and other industrial applications, according to MRAM-info.

Related: 'Universal memory' breakthrough brings the next generation of computers 1 step closer to major speed boost

Interaction between a magnetic material and radiation is well established when they are in equilibrium, but less is known about this relationship when they are not in equilibrium. It's also an area that overlaps with the weird laws of quantum mechanics, which are being harnessed to build quantum computers.

"We've arrived at a very elementary equation describing this interaction. It lets us completely reconsider optical magnetic recording and navigate our way to a dense, energy-efficient, cost-efficient optical magnetic storage device that doesn't even exist yet," Capua said.

Previous efforts to use the magnetic component of a light beam to flip a magnetic bit in this way were not effective, Capua said. But the new equation could help researchers to successfully incorporate the mechanism, he said.

In the far future, this technology could lead to MRAM components that are faster and more efficient than today's state-of-the-art RAM units, he added.

Optical cycle times (the time for an optical electromagnetic wave to complete an oscillation, in megahertz) in the technology could be a million times faster than in conventional memory. Electrical cycle times operate on nanoscale timescales (a second is 1 billion nanoseconds) whereas typical optical beams work in picoseconds (a second is 1 trillion seconds). 

It may also one day lead to quantum memory for quantum computers, in which a beam of light can fix a magnetic bit in neither 0 nor 1 but a superposition of the two states — much like how qubits work in quantum computers. Even though that's beyond the precision engineering of today, Capua said his team's findings could lead to the discovery of materials that could one day be used in such technology.

It can also make digitized memory systems more energy-efficient by giving the device more control over the strength and duration of the light beam and its effects. "The duration of the optical beam and its energy can be chosen to reduce the writing power. Obviously, when the device is idle it doesn't consume any energy since magnetic memories are nonvolatile," he said.

Artificial intelligence (AI) chatbots are terrible at remembering things — both between separate conversations and even during the same conversation. But two recent breakthroughs might completely change this.

If you talk to a large language model (LLM) like OpenAI's ChatGPT for long enough, it will begin to forget crucial pieces of information — especially if the conversation stretches on for more than 4 million words of input. Its performance then begins to deteriorate rapidly. 

Meanwhile, ChatGPT and other LLMs can't retain information between conversations. For example, if you finish one conversation and reboot ChatGPT a week later, the chatbot won't remember anything from the previous exchange. 

But two separate teams have potentially found solutions to these memory issues. A team of scientists led by the Massachusetts Institute of Technology (MIT) have pinpointed the reason AI forgets things mid-conversation and come up with a method to fix it, while developers at OpenAI have begun testing long-term memory, in which you can tell ChatGPT to remember parts of conversations, ask it what it remembers and later tell it to forget something — or wipe its memory completely. 

Improving mid-conversation performance 

The scientists found that they could improve chatbots' short-term memory by changing how the key-value cache — the chatbot's short-term memory — stores and replaces tokens, where one token is a chunk of input text. The scientists dubbed their new approach "StreamingLLM" and presented their findings in a paper published on Dec. 12, 2023 in the pre-print server arXiv. 

Related: ChatGPT will lie, cheat and use insider trading when under pressure to make money, research shows

A chatbot's memory is limited, so it evicts the oldest tokens and replaces them with newer tokens as the conversation continues. But applying StreamingLLM to an LLM means it can retain the first four tokens — before evicting the fifth token onwards. This means it will still forget things — because of the nature of its limited memory — but remember the very first interactions.

The order of the tokens (and whether they are labeled first, second, third, and so on) also matters because they feed into an "attention map" for the active conversation. This maps out how strongly each token relates to other tokens.

For example, if the fifth token is evicted, you may expect the sixth token to become the new fifth token. But for StreamingLLM to work, tokens must remain encoded as they were originally. In this example, the sixth token must not be encoded as the new "fifth" token just because it is now fifth in line — but remain encoded as the sixth token. 

These two changes mean a chatbot performs just as effectively beyond 4 million words as it did before, the scientists said in their paper. It's also 22 times faster than another short-term memory method that avoids performance crashing by constantly recomputing part of the earlier conversation.

"Now, with this method, we can persistently deploy these large language models. By making a chatbot that we can always chat with, and that can always respond to us based on our recent conversations, we could use these chatbots in some new applications," said study lead author Guangxuan Xiao, an electrical engineering and computer science graduate student at MIT, in a statement.

StreamingLLM has already been incorporated into Nvidia's open source LLM model optimization library called TensorRT-LLM — which is used by developers as a foundation for their own AI models. The researchers also plan to improve StreamingLLM by designing it to find and reincorporate tokens that have been evicted if they're needed again.

ChatGPT will never forget

OpenAI is also testing a method to improve ChatGPT's long-term memory, so that users can continue conversations and effectively build a working relationship with the AI chatbot.

When conversing with the LLM, users can ask ChatGPT to remember something specific or to grant it autonomy to remember elements of the conversation that it deems appropriate to store for later. These memories are not linked with specific conversations, so deleting chats does not erase memories — the memory itself must be deleted in a separate interface. Unless these are manually deleted, starting a new chat will pre-load ChatGPT with previously saved memories. 

OpenAI provided several examples of how this would be useful. In one example, the chatbot remembers that a kindergarten teacher with 25 students prefers 50-minute lessons with follow-up activities, and recalls this information when helping them create a lesson plan. In another, somebody tells ChatGPT their toddler loves jellyfish — and the AI tool remembers this when designing a birthday card for them. 

The company has rolled out the new memory features to a small portion of ChatGPT users, representatives said in a statement on Feb. 13, ahead of a planned broader rollout to all users. 

OpenAI will use information from memories to improve its models, company representatives said in the statement. They added, however, that scientists are taking steps to assess and mitigate biases and prevent ChatGPT from remembering sensitive information like health details unless a user explicitly asks it to. Users with memory access can also use a "temporary chat" in which memory is deactivated entirely. 

People with depression may struggle to recall specific memories about their lives — for instance, a dinner party with friends or a visit to their favorite coffee shop. Now, a small trial suggests that "scent therapy" could help people with depression unlock those difficult-to-access autobiographical memories (AMs).

The trial, described Tuesday (Feb. 13) in the journal JAMA Network Open, included 32 adults with major depressive disorder and used familiar scents — such as coffee grounds, oranges and Vicks VapoRub — as prompts for the participants to recall specific memories. So, for example, if presented with coffee, a person might think of meeting up with their sibling for lattes on a specific spring afternoon, as opposed to just generally thinking of the local cafe they often visit.

Previous studies had tried similar memory tests but instead used words and pictures as cues for the participants. So, in the new trial, the scientists switched between scents and words as cues, to see if one type of trigger might be more effective at jogging people's autobiographical memories. They found that the participants recalled more specific memories when cued by smell.

Related: How does the brain store memories?

"It was surprising to me that nobody thought to look at memory recall in depressed individuals using scent cues before," senior study author Kymberly Young, an associate professor of psychiatry at the University of Pittsburgh, said in a statement. Scents are known to trigger strong, often emotional, memories in a unique way that other stimuli don't necessarily do.

"The olfactory system is the only sensory system that has a direct, superhighway access to the memory centers of the brain and the emotional centers of the brain," Michael Leon, a professor emeritus of neurobiology and behavior at the University of California, Irvine, who wasn’t involved with the new study, told NBC News. "All the other senses have to take the side streets to get there."

So, in theory, harnessing smell might be a good strategy for rewiring those emotional centers in depression and unlocking the memories they help to recall. "If we improve memory, we can improve problem solving, emotion regulation and other functional problems that depressed individuals often experience," Young said.

That's because, when it comes to memories, people with depression have a bias toward lumping individual events into broad categories and overgeneralizing the emotions tied to those events. For instance, a person might recall "time spent in college" as one category and paint that whole chapter of life as negative, without being able to pluck out individual, positive memories from that time.

This memory bias keeps the person entrenched in negative thinking patterns that are difficult to break. For instance, it can make it more difficult for a person to debunk negative, overgeneralized thoughts about themselves, such as "I am a failure."

The trial sought to disrupt those patterns by helping people recall specific memories. Study participants were asked to recall memories — positive or negative — after sniffing 24 odor samples from glass jars or after hearing words that described those odors. The odors covered a broad range, including lavender, cumin, whiskey, cough syrup and shoe polish.

"In the verbal cue condition, 52% of memories were specific, while in the odor cue condition, 68% of memories were specific," the study authors wrote in the paper. "Additionally, we found that these AMs are rated more arousing and vivid upon recall," compared with the memories cued by words, they noted.

The team plans to run future trials with the addition of brain scans, to see how the amygdala, a key emotion-processing hub in the brain, responds to the treatment.  

"We hope this initial study spurs larger studies in more diverse samples that include healthy control participants" — meaning people without depression — "to further investigate and explain these associations," they concluded.

This article is for informational purposes only and is not meant to offer medical advice.

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Mouse, insect or worm — in all these creatures, the same principle guides the formation of super strong connections between neurons in the brain, a new study confirms. The research helps validate the idea that, regardless of species, there's a universal mechanism that underlies how brain networks form.

Different animals carry contrasting numbers of neurons in their brains, ranging from hundreds in worms to tens of billions in humans. Neurons form connections with each other, called synapses, that enable information to pass from one region of the brain to another in the form of electrical signals. Together, these connections form a network that enables animals to function and process information about the world. 

This network is flexible; it is always changing and rearranging. Some of the connections between neurons are fairly weak and thus easily broken and replaced, while a small group are super strong. These strong links are known as "heavy-tailed" connections because, on a graph of connection density in the brain from low to high, they're the outliers plotted at the dense end of the scale — like the tail of an animal. 

These heavy-tailed connections play a bigger role in controlling major cognitive processes, such as learning and memory, compared with the weaker connections that far outnumber them in the brain. However, it was unknown whether these strong links formed via simple, known principles of network organization or via mechanisms that were species-specific, according to the authors of the new study, published Wednesday (Jan. 17) in the journal Nature Physics. 

Related: 3D map plots human brain-cell 'antennae' in exquisite detail

"It has been known for some time that the number of neurons that a neuron is connected to varies widely with some neurons in the network being highly-connected hubs," Marcus Kaiser, a professor of neuroinformatics at Nottingham University in the U.K., who was not involved in the research, told Live Science in an email. 

"However, across species, the distribution of weights [strengths] of a connection also varies widely," he said. The team wanted to see if this variation might stem from differences in how each species' brain comes to be wired. 

The authors analyzed maps of the wiring between neurons, called connectomes, based on the brains of mice, fruit flies and two worm species. They created these maps by analyzing tissue samples with specialized imaging techniques. 

To deduce how heavy-tail connections may form, they used the data from the connectomes to develop a mathematical model based on a principle of neuronal self-organization known as Hebbian plasticity. This principle can be summed up with the phrase "neurons that fire together, wire together." In other words, when one neuron repeatedly activates another via chemical messages, the connection between the two cells gets stronger. This basic principle underlies how we learn and form memories. 

However, some previous research has suggested that Hebbian dynamics alone may not completely explain animals' ability to rewire their synapses and strengthen connections between neurons. 

The authors' model confirmed that Hebbian plasticity explained the formation of heavy-tail connections in all of the animals they studied, without the need for additional mechanisms specific to each species. In addition to explaining heavy-tailed connections, this principle likely guides neurons' tendency to cluster together and form tightly knit groups depending on their activity levels, the researchers said. 

To make their model better resemble a real brain, the authors ensured it accounted for some randomness in its network organization, they said in a statement. They assumed that neurons would typically rearrange and connect due to their activity, as in Hebbian dynamics, or randomly, with synapses sometimes disconnecting or forming without clear reason, Christopher Lynn, first author of the new study who conducted the research while at the City University of New York (CUNY) Graduate Center, said in another statement. 

"Overall, this is a promising first step to explain the variation in synaptic weight [the strength of connections between neurons] across biological neural networks," Kaiser said. 

However, a limitation of the article may be that the authors only compared a few features in their model to real neuronal networks, he said. For example, they tested clustering with their model but not other features you'd expect to see in brain networks with heavy-tail connections, he said. These include modules — densely connected regions of neurons — and short overall path lengths, meaning the distance between the cells. 

The authors didn't study human brains in the work, but they think that studying this seemingly universal principle of network development could help scientists better understand the structure and function of the brain in many animals, including humans. 

"These findings could help us better understand how the variety of connections arises in the human brain and how the brain heals and recovers after injuries," Dietmar Plenz, principle investigator at the National Institute of Mental Health, who was not involved in the research, told Live Science in an email. 

Editor's note: This article was updated on Jan. 18, 2024 with a quote from Dietmar Plenz. The story was first published on Jan. 17, 2024.

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Perhaps the most mysterious organ in the body, the brain continues to astound scientists despite the countless hours they've spent attempting to decipher its inner workings. Each new discovery about the brain brings a thousand new questions in its wake.

Here are 18 things we learned about the brain in 2023 that blew our minds.

Related: Do we really use only 10% of our brains?

1. Newly discovered part of the brain

In January, scientists described their discovery of a kind of shield in the brain that helps clear away waste and acts as a look-out post for immune cells. The thin shield seems to help control the flow of proteins and molecules between different compartments containing cerebrospinal fluid, a colorless liquid that flows around the brain and within tubes through the organ.

2. Squid and human brains tied by evolution

Despite the 500 million years of evolution that separate squids and humans, our brains develop in a very similar way to the brains of these cephalopods. Scientists discovered this by monitoring stem cells called neural progenitor cells in developing squid embryos. To build a squid retina, where most of the animal's neural tissue is found, the cells must first form a long, densely packed structure that can also be spotted during the neural development of vertebrates like us.

3. 'Junk DNA' and big brains

The genes that enabled humans to grow notably big brains may have originally come from "junk DNA," which doesn't code for any proteins, researchers revealed early this year. At some point in human evolution, after we split from other primates, some of this junk DNA picked up the ability to encode proteins. In animal and lab-dish experiments, several of these genes appeared key for boosting brain growth.

4. Injuries plugged with minibrains

Scientists used cerebral organoids — miniature 3D models of the brain — to repair brain injuries in rats. The organoids were grown from human stem cells and transplanted into rats' visual cortices, the region of the brain where information from the eyes is initially processed. The researchers hope to eventually apply the technique in humans, but that's many years away.

5. Native language wires the brain

A person's native language may influence how their brain links up information-processing hubs within its structure, according to a study of people whose native languages were German and Arabic published in February. Differences in the study participants' brains were chalked up to linguistic differences between the languages. However, more work is needed to reveal how cultural features of conversation might shape brain structure.

6. Psychedelics invade brain cells

Psychedelics have shown promise as therapies for hard-to-treat depression, and now scientists think it may be because they invade brain cells. Psychedelics, such as LSD, DMT and psilocybin, can bind to receptors for the chemical messenger serotonin — but significantly, they can latch onto these receptors on the outside and inside of cells. Theoretically, this means psychedelics might flip switches that traditional antidepressants, which generally increase the concentration of serotonin outside the cells, can't reach. That may be why trippy drugs drive brain cells toward building new connections.

7. Never-before-seen brain wave

Octopuses generate a type of brain wave not seen in any other animal, even humans. These long-lasting, unusually slow brain waves were recorded using electrodes implanted in freely moving octopuses' brains. Scientists aren't yet sure what function these unique waves serve, or if they're tied to a specific behavior.

8. Short-circuiting chronic pain

The brains of people with chronic pain show fluctuating patterns of activity that can be tied to the subjective experience of their pain, researchers have discovered. Deciphering these patterns could someday enable doctors to disrupt them with targeted therapies, thus short-circuiting patients' pain.

9. Brain surgery in the womb

In a first-of-its-kind surgery, doctors repaired a malformed blood vessel in a fetus' brain prior to birth. The malformation occurs in an estimated 1 in 60,000 births and is usually treated after birth, when it can sometimes be too late to prevent damage or death. In March, doctors successfully treated the malformation sooner, in the womb.

10. Life flashing before your eyes?

People's brains generate a flurry of activity in their last minutes of life, scientists revealed in May, and this electrical surge may reflect conscious experiences — however, that's just a theory. It could be that this activity erupts as people "move toward the light" or see their "lives flashing before their eyes," as portrayed in many movies. Or, it could also just be "aberrant electrophysiological activity," some experts say.

11. Mystery brain spiral signals

Spiral signals uncovered in the human brain may help organize the organ's complex activity. The spirals are brain waves that pass over the surface of the brain and rotate around central points. These spirals may act as bridges of communication between different regions of the brain, scientists theorized in June.

12. Sex switch in mouse brains

Scientists discovered an "on switch" for libido in the male mouse brain — and they think a similar control center may exist in humans, although they haven't found such circuitry yet. Flipping the switch drove male mice to mate with females and with inanimate objects, and also reduced the break time needed between rounds of sex. As of now, no equivalent circuit has been found in female mice.

13. Pink Floyd in brain waves

In August, scientists revealed they were able to "read" people's brain waves and recreate Pink Floyd's famous "Another Brick in the Wall," which the volunteers had listened to during their brain recordings. Some song snippets generated by the researchers really did sound like the 1979 protest song — other snippets, however, sounded much muddier.

14. A 'tell' for false memories

Your brain's activity shifts in a distinct way when you're about to recall a false memory, or one in which the events never really happened. This "tell" specifically crops up in the hippocampus, a key brain region for memory, scientists recently discovered.

15. Brain changes across menstrual cycle 

The brain's structure goes through subtle changes throughout a person's menstrual cycle. These changes appear in the microstructure of the brain's white matter — the insulated wires that run between brain cells — as well as the thickness of its gray matter, the bodies of brain cells. For now, it's unknown whether these brain changes affect cognition or the risk of brain diseases. But the research could open the door to such discoveries in the future.

16. Complete insect brain map

The first-ever complete map of an insect's brain contains 3,016 neurons. The fruit fly brain atlas, completed over 12 years and finally revealed in June, shows all the physical connections between the thousands of cells. It could help pave the way for more-advanced artificial intelligence (AI) systems and help scientists decipher similar structures in the human brain.

17. Most-complete human brain map ever

This year, scientists unveiled the most detailed atlas of the human brain ever conceived which details the arrangement of 3,300 types of brain cells, few of which were previously known to science. The atlas is half composed of neurons — the brain cells that communicate through chemical and electrical messages — and half made up of non-neuronal cells.

18. Minibrain plugged into AI

For the first time, scientists plugged a brain organoid into the middle of an AI system and used the hybrid computer to perform tasks and computations. The experiment could help pave the way for biocomputers that borrow tricks from biology to become more energy efficient than standard computers.

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An internal "clock" attached to a person's DNA may be a better predictor of age-related memory decline than their actual, chronological age, a new study suggests. 

As people age, they tend to gradually lose the ability to process information and retain memories. How quickly and to what extent this happens differs between individuals, meaning that simply looking at a person's chronological age is not enough to predict these changes. 

An alternative way to measure aging is to look at chemical tags that latch onto DNA and alter how genes are expressed, without changing the underlying genetic code. Called "epigenetic aging," the addition of these chemical tags happens over time and can be influenced by a person's behavior and environment, differing depending on their stress and diet, for example.

In the new study, published Monday (Oct. 30) in the Journals of Gerontology: Series A, scientists measured the epigenetic "clocks" of 142 adults who were aged between 25 and 65 years old, before asking them to complete daily memory tests on their phones. The authors found that the volunteers' epigenetic ages better reflected how they differed from each other in their cognitive performance than their chronological ages did. The epigenetic ages also captured how each person's performance varied over a short period of time. 

Related: Scientists find 10 'markers' in blood that predict people's chances of reaching 100

"The study is the first of its kind, to our knowledge, that has examined how these epigenetic aging clocks predict in daily life how well people remember and how quickly they perform mental tasks," senior study author Stacey Scott, an associate professor of psychology at Stony Brook University in New York, told Live Science in an email. 

"Previous studies have found this pattern when testing people in the laboratory, but this hasn't been done in everyday life," she said. 

To determine the volunteers' epigenetic ages, the researchers looked across their genomes for patterns of DNA methylation — a type of epigenetic modification where molecules called methyl groups stick to DNA. Individuals' epigenetic ages were deemed to be "older" or "younger" depending on methylation levels at key spots in the genome that are known to vary with age. 

The researchers then asked the volunteers to complete daily tests that assessed working memory, meaning their ability to temporarily retain small bits of information and use it to complete tasks, as well as their processing speed, or how long it took them to react to and complete the next round of the test. 

On average, the volunteers completed around 60 tasks in the two-week study period.

"Because we had people complete these 'brain games' assessments many times," the team was able to examine not only the participants' typical performance but also find out how consistent they were in their scores, Scott said. 

On average, the authors found that people whose epigenetic age was judged as older than their chronological age performed worse in both the processing speed and working memory tasks than those whose epigenetic age matched or was younger than their true age. (Perhaps unsurprisingly, chronologically younger people also performed better in the tasks than older volunteers.)

The performance of those with relatively old epigenetic ages was also less consistent between tasks compared with the other volunteers, suggesting that epigenetic age could be a better predictor of memory function than chronological age. 

Further research will be needed to assess how epigenetic age relates to longer term changes in cognitive performance, as well as determine which parts of the aging process these chemical markers reflect, the authors wrote in the paper. Going forward, they'd also like to investigate other measures of cognitive ability and types of epigenetic modifications beyond methyl groups.

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Your brain activity changes depending on whether you're recalling a true or a false memory, new research suggests. A "false" memory refers to when you remember something that didn't happen or that actually occured at a different time or place. 

Remembering past events, experiences or information tied to a specific context, such as a birthday party, first date or recent trip to the grocery store, is known as episodic memory; that's opposed to semantic memory, which is related to general knowledge and facts untethered to a time or place and not related to one's own past. Episodic memories are largely controlled by a brain region called the hippocampus, but what happens in the brain structure when people misremember events has been a mystery — until now. 

According to the new study, published Sept. 26 in the journal PNAS, a specific pattern of electrical activity erupts in the hippocampus immediately before someone recalls a false memory — and it differs from the electrical activity that occurs when people remember an event correctly.  

"Whereas prior studies established the role of the hippocampus in event memory, we did not know that electrical signals generated in this region would distinguish the imminent recall of true from false memories," Michael Kahana, senior study author and a professor of psychology at the University of Pennsylvania, said in a statement. 

Related: Neurons aren't the only cells that make memories in the brain, rodent study reveals

A better understanding of this brain activity could help predict when people are going to recall a distressing false memory, far removed from its original context, the study authors suggested.    

For example, people with post-traumatic stress disorder (PTSD) "often experience memory intrusions of their traumatic experiences under contexts that are safe and dissimilar to the traumatic incident," they wrote in the paper. In theory, new medical treatments could be designed to monitor and disrupt this brain activity to put a stop to the disturbing flashbacks, the study authors proposed.

In the new study, the researchers recorded electrical activity in the hippocampus of patients with epilepsy, who'd already had electrodes implanted in their brains so doctors could track their seizures. The team initially asked the patients to study a list of unrelated words, such as "pizza" and "clock," and then recall them in any order after a brief break. Before studying the "target" word list, the participants had been shown a different list of words that could potentially trip up their memories. In such tests of episodic memory, the words are contextually bound together by their source, meaning the word list on which they're presented.   

The rhythm of electrical activity in the hippocampus differed dramatically when patients correctly recalled a word from the target list or incorrectly remembered one that hadn't been included. This electrical activity appeared less than a second before they said the word and then faded quickly afterward.

Interestingly, if a patient incorrectly recalled a word from the other list they'd been shown, their hippocampal rhythms were more similar to those seen when they recalled correct words. The rhythm differed most significantly when they said a word they'd never been shown. The authors hypothesized that this was likely because the patients were in the same situational context — sitting at the same seat in the same room — when they stored the memories of the words on both lists. In other words, the shared context made the memories more similar to one another in the brain.

In a second experiment, the authors asked the patients to study and recall related words, categorized as flowers, fruits and insects. The importance of situational context was also shown in this test. For example, after a patient studied the flower list, if they recalled an incorrect but similar word, such as "sunflower" instead of a "lily," their hippocampal rhythm was more similar than if they'd recalled a word that was completely unrelated, such as "clock." 

The authors wrote that these findings may explain how the hippocampus distinguishes between similar memories made in different contexts — for example, what you cooked for dinner tonight versus last night. And it may pave the way for new therapies to treat diseases where memory recollection goes haywire. However, it's still unclear whether these electrical signatures are actually responsible for the false memories or just happen at the same time. Future studies could explore this by experimentally manipulating brain activity, the authors wrote. 

Neurons, the brain cells responsible for relaying chemical and electrical messages, have long been considered the key players in memory formation — but new research in rodents suggests that the cells may have an unsung-but-crucial collaborator. 

The findings could have implications for research into memory and associated diseases, such as Alzheimer's disease. 

Found in the walls of tiny blood vessels called capillaries, the collaborators, called pericytes, are crucial for regulating blood flow in the brain, forming blood vessels, controlling the entry of immune cells into the central nervous system, and constituting and maintaining the blood-brain barrier, a thin border of cells that allows only select molecules to move between the brain and blood. 

In addition to these jobs, pericytes also work with neurons to form and store long-term memories, according to a study published Monday (Oct. 2) in the journal Neuron. 

"We now have a firmer understanding of the cellular mechanisms that allow memories to be both formed and stored," Cristina Alberini, senior study author and a professor of neural science at New York University (NYU), said in a statement. "It's important because understanding the cooperation among different cell types will help us advance therapeutics aimed at addressing memory-related afflictions," she added. 

Related: How does the brain store memories? 

In the new study, the authors looked at a protein called insulin-like growth factor 2 (IGF2), whose production surges in the hippocampus, a key region of the brain for making long-term memories, after learning. For example, there's an uptick in IGF2 after an animal is trained to be fearful of scenarios that they've come to associate with a mild electric shock to the foot. 

In mice and rats, the researchers found that pericytes produce most of this IGF2 in the hippocampus. This production seemed to be triggered by the activity of nearby neurons; when starting to form memories, neurons in the hippocampus send each other a flurry of chemical messages and the channels of communication between those cells begin to grow stronger. The researchers aren't yet sure how this activates the nearby pericytes, but it does seem that the neurons kick off the memory-making process.  

In other experiments, the researchers stopped pericytes from producing IGF2 but didn't stop other types of cells from doing so, such as neurons and connective tissue-making cells called fibroblasts. This not only hindered the rodents' ability to make long-term memories — for example, of objects they'd been trained to recognize — but also blocked the action of genes that normally switch on in neurons during memory making.

Taken together, these experiments suggest that pericytes need to produce IGF2 for neurons to successfully make long-term memories.

Going forward, the authors want to explore whether IGF2 engages with other types of cells in the brain and whether similar collaborations between neurons and pericytes happen elsewhere in the brain. In their paper, they wrote that it would be valuable to understand whether this mechanism involves all of the pericytes in the hippocampus or only a selective group of them. 

The findings may improve our understanding of brain diseases that involve the loss of long-term memories, such as Alzheimer's disease, which has also been linked to dysfunctioning pericytes.

"This work connects important dots between the newly discovered function of pericytes in memory and previous studies showing that pericytes are either lost or malfunction in several neurodegenerative diseases, including Alzheimer's disease and other dementia," study co-author Benjamin Bessières, a postdoctoral researcher at NYU, said in the statement. 

But more research is needed, particularly in humans. 

"Our study provides a new view of the biology of memory — though more research is needed to further understand the roles of pericytes and the vascular system in memory and its diseases," Alberini said in the statement. 

Ah, the nostalgia of childhood memories — that cherished first bicycle ride, the debut dip in the ocean, the distinctive patterns of wallpaper long since removed from the family home. These early recollections are often steeped in sentimentality and woven into the fabric of our identity. But can they be trusted?

In other words, how reliable are our memories? As it turns out, they are usually fairly accurate, especially if the events we are recalling are scary or painful.

In two minds

Still, Carole Peterson, a child psychologist and professor at Memorial University of Newfoundland who specializes in early childhood memory, told Live Science that our memories are not infallible, and both children and adults can have recollections that are not entirely accurate.

"Memories from every age can be malleable," Peterson said. "This is not unique to early memories. At all ages, we are susceptible to suggestion, although it is true that younger children are more susceptible than older children or adults."

Related: Can you recover repressed memories?

Research has found that people often forget events relatively quickly after they happen, especially if they were run-of-the-mill. In a 2020 study published in the journal Psychological Science, researchers found that people had fewer memories of real world events the more time had passed since they happened. The memories were also less detailed as more time had passed. However, the team also noted that when the participants did successfully recall an incident, they were accurate 93% to 95% of the time, no matter how much time had passed.

So, what does this mean in terms of establishing the veracity of our first memories?

In a study published in the journal Child Development in 2011, Peterson and colleagues interviewed children ages 4 to 13 about their earliest memories and re-interviewed them two years later. They found that "events infused with emotion were more likely to persist." In addition, if the child had a clear memory rather than a confused one — for example, if it was organized and chronological — it was more likely to be recalled.

Additionally, Peterson's research has found a strong link between emotion and accurate recall. If an event is particularly harrowing or painful, for example, the quality of the memory is often higher.

This is supported by a 2015 study in which researchers interviewed preschoolers about an injury serious enough to require hospital treatment. They then followed up a decade later to see what the adolescents remembered of their childhood injury, Peterson said. Researchers also interviewed adults who witnessed the injuries shortly after they occurred to serve as the "accurate" record.

"The adolescents were remarkably accurate in recalling the details of these very early emotional and salient events," Peterson said. "We were surprised by this."

In some cases, people — and children in particular — can form false memories, or vivid recollections of events that never happened. In German psychiatrist Michael Linden's 2013 book "Hurting Memories and Beneficial Forgetting," Linden states that high social expectations can lead to the development of false memories in children who learn to respond as expected. These false memories can be remarkably realistic and detailed, making them hard to distinguish from real memories.

A 2011 study published in the journal Medical Hypotheses attempted to determine why false memories occur. The researchers suggested that "emotional-facilitation is prominent in false memories," adding "emotions may overwhelm or supersede the feelings of uncertainty, or doubt tag, for an incorrect memory." The study's authors also noted that "suggestibility" appears to be a key factor in false memories, before concluding that "the very notion of false memory stands as a challenge to our self-image as rational, veridical reporters of actual events."

Related: Do we really use 10% of our brains?

Fact from fiction

Many people's earliest memories are banal, sketchy or abstract. So, given we tend to remember emotional events with a greater degree of clarity, how likely are these more uneventful recollections to be precise?

Peterson published a study in 2017 in which children ages 4 to 9 initially recalled their very earliest memories and were asked about them again eight years later. "With some very general hints, they recalled most — but not all — of the events, but the specific content they mentioned often differed," Peterson said.

For kids who were ages 6 and up at the time the initial memories were made, very little content was contradictory, but it differed in terms of what they chose to talk about, Peterson said. "For example, when relating a particular camping trip, they often described different components. Children who were 4 or 5 at the time of the initial interview, however, were much more likely to contradict what they had said earlier."

Ultimately, Peterson said, it is very difficult to determine the "true" accuracy of a memory, especially when it comes from early childhood, unless the event was recorded and video evidence exists.

Napping during the day is an ancient custom that is practiced worldwide.

While some people view napping as a luxurious indulgence, others see it as a way to maintain alertness and well-being. But napping can come with drawbacks as well as benefits.

As an orofacial pain specialist, I have extensive education in sleep medicine and how sleep impacts wellness, due mostly to the relationship between sleep and painful conditions such as headaches and facial pain. My training involved all aspects of sleep, especially sleep breathing disorders, insomnia and sleep-related movement disorders.

As such, I'm aware of the complex nature of napping, and why a short nap — that is, a nap during the daytime that lasts from 20 to 30 minutes — may be beneficial in myriad ways.

Related: What happens in your brain while you sleep?

An abundance of health benefits

Research shows that there are many benefits to napping. Short naps can boost mental functioning and memory, as well as improve alertness, attention and reaction time.

Short naps are also linked to increased productivity and creativity. Because napping seems to improve creative thinking, some companies have attempted to harness this by introducing napping rooms into the workplace.

What's more, it appears the brain uses nap time to process information gathered throughout the day, which appears to enhance problem-solving abilities. One small study revealed that people who took short naps were less frustrated and impulsive, which resulted in better focus and efficiency when performing work-related tasks. Napping may even lead to an improved ability to learn new motor skills, such as a golf swing or the playing of a musical instrument. This is because these memories or skills become consolidated in the brain during sleep, whether at night or while napping.

Napping can also reduce stress. One study found that naps of approximately 20 minutes improved the overall mood of participants. However, longer naps lasting more than 30 minutes are not typically associated with improved mood and increased feelings of well-being.

Short naps may also be associated with a reduced risk of cardiovascular diseases. If we are awake more than we should be, we tend to have a buildup of the "fight or flight" chemicals in our bodies. Studies show that more consistent sleep will help lower these chemicals, resulting in a normalization of blood pressure and heart rates. Napping appears to help this process for some people.

But just as in nighttime sleep, some people may have trouble drifting off for a nap, especially when they have limited time. Progressive muscle relaxation techniques have been shown to be beneficial for both nighttime sleep and napping. Other nonspecific relaxation techniques, like listening to relaxing music, appear to also be beneficial for falling asleep. Interestingly, many people overestimate their time awake when trying to sleep and underestimate the time they actually spent sleeping.

Related: Human brain looks years 'older' after just one night without sleep, small study shows

Napping can have drawbacks

One condition associated with napping longer than 30 minutes is sleep inertia — the grogginess and disorientation that people sometime experience after waking from a longer nap.

Usually, the longer the nap, the more sleep inertia there is to overcome. This can impair cognitive function from several minutes up to half an hour. In many cases, these effects can be minimized by consuming caffeine directly after the nap.

But it is important to note that caffeine is not a substitute for sleep. Caffeine acts to temporarily block the action of a chemical known as adenosine, a sleep-promoting agent that builds up during waking hours. If you are habitually dependent on caffeine consumption to keep you awake and alert, it may suggest that there is an underlying sleep disorder such as insomnia or sleep apnea, in which a person temporarily stops breathing during sleep.

Long or late afternoon naps can also interfere with nighttime sleep, either by leading to difficulties falling asleep or staying asleep during the night. This disruption of the regular sleep-wake cycle can result in overall sleep deprivation, which can have numerous negative health effects.

What's more, for those age 60 and up, longer naps — beyond 30 minutes — may increase the risk for cardiovascular problems. Researchers found that older adults taking naps for more than one hour per day have a higher incidence of increased blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol or triglyceride levels, sometimes known as metabolic syndrome.

The reason for this phenomenon is mostly unknown. Older individuals tend to nap more frequently than younger adults partly due to more disturbed sleep during the night. This could be related to more pain or other health factors that will interfere with sleep, sleep altering medications and altered sleep rhythms seen with aging.

Best practices

So, to maximize benefits while reducing risks, here are some tips: Keep naps short to avoid sleep inertia and nighttime sleep disruptions. Nap in the early afternoon, as that aligns with a decrease in energy levels after lunch and with the body's natural circadian dip, which is an increase in sleepiness similar to what occurs at dusk. Avoid late afternoon naps, finish naps at least four to six hours before bedtime, and create the right environment by napping in a quiet, comfortable and dimly lit space.

If you're struggling with daytime sleepiness, it's best to address the root cause rather than relying solely on napping. Reducing caffeine consumption, maintaining a regular sleep schedule and getting adequate nighttime sleep are essential steps to reduce daytime sleepiness.

Ultimately, napping should complement a healthy sleep routine, not serve as a substitute for sufficient nighttime rest. A balanced approach to napping can contribute to a more energized, focused and resilient life.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

You're walking somewhere you've never been before and suddenly feel as though you've strolled down the same road already. You're experiencing the well-known phenomenon déjà vu — but what is déjà vu, really, and why does the strange feeling happen?

Déjà vu is a French expression meaning "already seen," which was first used in 1876 by French philosopher Émile Boirac in a letter to his book editor, and later in his published book "The Psychology of the Future" (Keagan Paul, 1918). 

Déjà vu is the feeling that something a person is currently experiencing has already occurred in the past. Experts refer to this phenomenon as a memory illusion involving familiarity and unfamiliarity, according to the book "Psychology of Learning and Motivation" (Elsevier, 2010). The illusion pits a person's impression that an experience is familiar against their knowledge that this sense of familiarity is inaccurate. An estimated two-thirds of people report experiencing déjà vu, the book states, and the frequency of reported episodes decreases with age.

Related: How does the brain store memories? 

Some people report experiencing déjà vu to a frequent degree that's disturbing to them. Such cases can be caused by substance abuse, migraine and anxiety, reports suggest, as well as depersonalization-derealization, a mental condition where a person feels detached from their body or surroundings. However, temporal lobe epilepsy is thought to be the most common cause of such frequent déjà vu. Scientists suggest that, at least in epilepsy, déjà vu episodes may arise from seizures in the brain's temporal lobe or dysfunction in brain regions involved in storing and retrieving memory, like the hippocampus and parahippocampus.  

However, given that déjà vu is also experienced by individuals without epilepsy or other conditions, there must be other explanations as to why the bizarre experience occurs.

"One possible mechanism is the memory-based theory which focuses on the role of familiarity and recognition in déjà vu," Dr. Ooha Susmita, an in-house neuropsychiatrist at Allo Health, told Live Science. This theory suggests that "Déjà vu arises when a current situation strongly resembles a previously encountered but forgotten experience," Susmita said. 

"The new situation may share similarities with a past event, leading to a sense of familiarity without an accompanying memory of the specific details." She added that déjà vu may result from our brain's attempt to make sense of these perceived similarities and create a feeling of recognition, even if we cannot consciously recall the original experience.

Historically, scientists have struggled to recreate déjà vu in the laboratory because it's difficult to identify stimuli that can evoke the feeling. But they've found ways around this challenge. (For example, in 2010, University of Leeds researchers even reported using hypnosis to induce déjà vu in volunteers.)

In a study published in 2012 in the journal Consciousness and Cognition, Anne Cleary, a professor of cognitive psychology at Colorado State University, and her team used virtual reality (VR) to investigate the hypothesis that people may experience déjà vu when they encounter environmental layouts that are similar to those experienced in the past, provided that they don't recall that past experience. This is called the "Gestalt familiarity hypothesis," built on the arrangement of items in an environment.  

In their experiment, Cleary and her team attempted to trigger déjà vu in participants by having them navigate different scenes with a VR headset; some scenes shared the same spatial layout, meaning their walls and furniture were placed in the same locations, for example. The team found that people were more likely to report feelings of déjà vu when they found themselves in settings with a similar design to scenes they have seen in the past but didn't specifically recall.  

Another theory suggests that déjà vu results from perceptual gap, or split perception, according to "Psychology of Learning and Motivation." Split perception occurs when the brain processes the same sensory signals twice, back to back, at a particular moment. In the initial process, the signal is brief and often goes unnoticed in the conscious mind. During the second process, which follows almost immediately, feelings of familiarity (déjà vu) are established due to that first signal, which cannot be recalled. 

In 2016, Akira O'Connor, a lecturer at the school of psychology and neuroscience at the University of St. Andrews in Scotland, presented research that suggested that déjà vu is caused by the brain correcting memory errors, New Scientist reported. 

O'Connor and his team used a brain scanning technique called functional resonance magnetic imaging (fMRI) to check which parts of the brain are active when déjà vu is triggered in the lab. From their result, it was not the hippocampus, a key brain region responsible for memory retrieval, that was active, but the medial prefrontal cortex, a region involved in resolving conflicts between what we remember experiencing and what we've actually experienced. 

According to O'Connor, this region of the brain shoots off a signal when such a mismatch occurs, and this may explain why déjà vu is more common in young people than old. As a person gets older, déjà vu is not as frequent because "the general checking system is in decline," he told New Scientist, making it difficult for them to discern false memories.     

There is no universally agreed upon scientific theory that explains the mechanism behind déjà vu. More research is needed to explain this mysterious sensation, Susmita told Live Science.

"It is important to note that déjà vu is a common experience and is not considered to be a sign of any underlying medical or psychological condition," Susmita said. "While our understanding of déjà vu has advanced over the years, it remains a complex and intriguing phenomenon that continues to be the subject of scientific inquiry. Further research is needed to unravel the precise mechanisms involved in déjà vu."

A man in his 80s gradually started feeling that he was witnessing the same events again and again. This disturbing symptom, somewhat reminiscent of the 1993 movie "Groundhog Day," likely emerged as a rare complication of Alzheimer's disease, according to a new report of the case.

According to the report, published May 16 in the journal BMJ Case Reports, the man once complained to his e-book manufacturer because he thought it kept showing the same material, and he also contacted a technician about his television repeatedly showing the same news. 

When describing his predicament in his own words, he said, "Wherever I go, the same people are on the side of the road, the same cars behind me with the same people in them … the same person gets out of the cars wearing the same clothes, carrying the same bags, saying the same things … nothing is new."

This condition, called deja vecu with recollective confabulation (DVRC), is sometimes seen in neurodegenerative diseases such as Alzheimer's, according to the report. Neurodegenerative diseases are those in which cells of the central nervous system stop working and ultimately die. These conditions worsen over time, and no cures yet exist.

Related: A man's rare gene variant may have shielded him from devastating form of early Alzheimer's 

Deja vecu differs from the more familiar deja vu, the transient and strange feeling that you have experienced the present before. While deja vu describes a fleeting sensation, deja vecu is the persistent perception that new encounters are repetitions of previous experiences. 

Those with deja vecu often lack insight into their condition and develop disabling, delusion-like false beliefs and behaviors to justify their abnormal perception, the case report authors wrote. Collectively, this false perception combined with the production of false evidence to support it is known as recollective confabulation.

DVRC has been described in a handful of other patients with neurodegeneration, including some with Alzheimer's. The exact cause of DVRC remains elusive, but some have suggested that dysfunction of the hippocampus, a part of the brain that helps convert short-term memories into long-term memories, may give rise to a "false sense of recollection," the authors noted.

Deja vecu without recollective confabulation has also been seen in some neurological diseases, including temporal lobe epilepsy and traumatic brain injury, and in psychiatric disorders, such as schizophrenia. In one reported case, it was linked to a person taking 5-hydroxytryptophan, a compound that gets converted into the chemical messenger serotonin in the body. 

A neuropsychological assessment of the man in the recent case revealed memory loss, impulsive behavior and cognitive decline, and he often conflated two separate stories as being just one. Brain scans highlighted unusually low activity in the left temporal lobe, a region of the brain's wrinkled outer layer located behind the left ear, and the frontal lobes, with abnormalities being more pronounced on the right than on the left. 

Doctors also examined the man's cerebrospinal fluid (CSF), the fluid that surrounds and cushions the brain and spinal cord. They found that in the CSF, the level of the protein amyloid beta-42 was reduced, while the tau protein level was borderline elevated. These are signs of Alzheimer's disease. 

The man was treated with a trial of immunotherapy, likely because his doctors had also found antibodies in his CSF, but this treatment was discontinued following a lack of clinical improvement. Four years after the onset of his symptoms, the man scored worse on cognitive tests than he had during his initial assessment. 

"His recollective confabulation symptoms remain pervasive and bothersome," the case report authors wrote. Still, "he continued to live at home and remained independent with self-care."

The largest case series to document DVRC included reports of 13 patients, nine of whom had probable Alzheimer's. Three of the patients had mild cognitive impairment, and one had frontotemporal dementia, the case report authors wrote. They noted that their case report is unique in that it's the first report of DVRC that analyzed brain activity with scans, evaluated the patient's CSF  and included repeated neuropsychological testing.

Human beings can generate false memories of events mere seconds after they have occurred, a new study has found. 

The phenomenon, which researchers have dubbed "short-term memory illusions," shows how easily and rapidly humans reimagine experiences to fit our preconceptions, rather than accurately recording what takes place. The researchers published their findings April 5 in the journal PLOS One.

"It seems that short-term memory is not always an accurate representation of what was just perceived," the researchers wrote in the study. "Instead, memory is shaped by what we expected to see, right from the formation of the first memory trace."

Related: 'Muscle memories' get 'zipped and unzipped' in the brain, like computer files

To test the accuracy of short-term memories, the researchers enlisted 534 volunteers to take part in a series of four experiments, each designed around memorizing a sequence of letters of the Latin alphabet. 

In each round, participants were shown a collection of letters, arranged in a circle. Those letters would then disappear and a box would pop up at a specific position in the circle, to indicate which letter they should remember. Participants had to remember both the letter's identity and the direction it was facing, as some had been mirrored to face backwards. 

Sometimes, participants were shown a second, irrelevant batch of letters before their memory was tested. After giving the answer, they were then asked to score their confidence, from very low to very high, that they had guessed correctly. 

When the participants were asked to recall what they saw just a half second later, they were wrong just under 20% of the time, and this error rate shot up to 30% when asked three seconds later. When asked to recall whether a letter was facing forwards or backwards, participants who responded with high confidence had flipped the letter to its regular position 37% of the time, even though they had been explicitly warned that mirrored letters would appear in the tests and should not be mistakenly reported for real ones.

To confirm their findings, the researchers repeated the tests across three similar experiments with a cohort of 348 people not included in the original analysis, who showed the same tendency to mentally flip the mirrored letters. Across all experiments, this mental letter-flipping was the most common high-confidence error — a sign that human brains record experience based on preset notions (in this case, how a letter should appear) that enable us to generate better predictions about the world, while pruning out peculiarities that don't fit with those preconceptions.

"These memory illusions seem to be the result of world knowledge and not of visual similarities," the researchers wrote in the study. "Taken together, the results thus show that world knowledge can shape memory even when memories have only just been formed."

The researchers' next steps are to design experiments that could demonstrate similar short-term memory adjustments in real-world settings, as well as for other types of memory besides those related to visual and language-related stimuli.

Tapping into your "muscle memory" to tie your shoes or play an instrument may feel automatic — but to execute these learned motions, the brain erupts into a flurry of activity, rapidly "unzipping" and "zipping" all the key information about the movement being performed, a new study suggests.

The study, published Feb. 1 in the Journal of Neuroscience, used a brain scanning technique called functional magnetic resonance imaging (fMRI) to collect snapshots of people's brains as they played simple melodies on a keyboard. fMRI tracks the flow of oxygenated blood through the brain, and because active brain cells require more oxygen than inactive ones do, the scans provide an indirect measure of brain activity. 

The 24 study participants — none of them trained musicians — learned simple, one-handed keyboard melodies over several days and were then asked to play these sequences from memory while in the fMRI scanner. In each trial in the scanner, the participant would receive a visual cue to prepare to perform one of the melodies and then a second cue to execute it. 

In some of the trials, the participants weren't given the second cue, so the researchers got snapshots of the brain both planning and executing movements. 

Related: How does the brain store memories? 

These scans revealed that movement-related regions of the brain's wrinkled outer surface, the cerebral cortex, lit up during the planning stage, and this activity reflected the order and timing of the notes to come. In other words, specific patterns of brain activity reliably translated to particular sequences of notes, and separately, other activity patterns reflected the durations of those notes. 

"This happens very rapidly and automatically each time in the hundreds of milliseconds before the action starts," Katja Kornysheva, the study's senior author and co-director of the Centre for Human Brain Health at the University of Birmingham in the U.K., told Live Science in an email. 

Then, when it comes time to actually play the notes, these separate patterns representing note order and timing become integrated, or "zipped," resulting in a new, unique pattern of brain activity. 

"The integrated patterns were those that were unique for a particular combination of key-press order and timing, not something that transferred across these combinations," Kornysheva said. So the brain went from handling each element of the movement separately, like paint and a canvas, to considering them a single, integrated unit, like a completed painting. 

An established theory suggests that the parts of the cortex that control movement are in a kind of hierarchy, but this study runs counter to that idea, said Tanuj Gulati, an assistant professor of biomedical sciences at Cedars-Sinai Medical Center in Los Angeles who was not involved in the new research. 

Two regions, known as the premotor and parietal areas, are thought to store "high-level" information about movements — in this case, the order and timing of keystrokes. The primary motor cortex, which communicates with muscles via the spinal cord, handles only "low-level" information — what muscles in the fingers and forearms actually need to activate to make the keystrokes happen.

"This notion is challenged in this study," Gulati told Live Science in an email. "The areas thought to be 'low-level' that can only communicate fixed commands to downstream muscles were instead found to be constantly updating based on order and timing challenges of a movement," and so they were dynamically involved in movement planning and execution.

Kornysheva and her team are currently studying muscle memory in the context of disorders such as dyspraxia, a neurological disorder that affects the ability to plan and coordinate movements. Their work could also be useful for helping people regain motor skills after they've had a stroke, Kornysheva added. 

The team is also starting to study motor learning in trained musicians, in addition to novices, she said. 

"Musicians with seasoned finger proficiency and their sequence/timing control are akin to elite athletes, say a gymnast with excellent postural control," Gulati said. It may be that, in highly trained individuals, certain movement sequences become "hardwired" in the motor cortex and the rapid adjustments to high-level features of those movements may unfold differently than they do in the brains of novices, he said.

They say "an elephant never forgets." But how much truth is there to that expression? How good is an elephant's memory?

Though it's not strictly accurate to say an elephant never forgets, the pachyderms did evolve to remember details that are key to their survival. For example, elder African elephants (Loxodonta africana) can recall the unique sounds and smells of predators (even discriminating between different groups of people, depending on their odor and clothing color), retrace their steps to find water holes in the arid savanna, and distinguish family members and associates from hundreds of other elephants.

"Being able to seek out sufficient food and water in a highly dynamic environment such as the savanna, while also managing complex social relationships and avoiding predation risk, requires a brain capable of processing and remembering detailed information," Graeme Shannon, a lecturer in zoology at Bangor University in the U.K., told Live Science in an email. "This is a critical skill that can mean the difference between life and death."

Elephants are not the only animals that forage for food in the savanna, but the unique challenges these pachyderms face demand exquisite memories. For instance, each elephant needs to eat about 330 pounds (150 kilograms) of vegetation each day, and to satisfy their voracious appetites, elephants embark on long migration routes between the wet and dry seasons. Whether they survive that migration depends heavily on their knowledge of the route.

"An elephant's memory facilitates remembering long migration routes that include tree and water resources, which are important in order to make it through a very long migration," Caitlin O'Connell, a faculty member at Harvard Medical School who studies elephant hearing, told Live Science in an email. 

Related: Do elephant tusks or rhino horns ever grow back?

Memory becomes particularly important during a drought. A 2008 study in the journal Biology Letters observed that elephant herds with older matriarchs, who had lived through prior droughts, successfully led their herds to water — presumably by remembering how the herd had survived the prior drought.

One herd, however, was led by a young matriarch that could not have remembered how the previous generation had handled the last drought. Her herd stayed put rather than traveling through new terrain to find water, and its calves suffered a 63% mortality rate that year. The normal fatality rate during a drought is only 2%. "Hence the importance of older matriarchs as important repositories of knowledge," said O'Connell, who was not involved in the study. "And hence why long-term memory can lead directly to survival."

Elephants also need their memories to navigate what biologists call a "fission-fusion" dynamic. In this arrangement, also common among primates and some whale species, a core family unit of elephants comes into contact with hundreds of other elephants over the course of the year (fusion), only to later break off into the same core group (fission). 

"Operating in a highly complex social world takes considerable brain power," Shannon said. "It is crucial that elephants have detailed knowledge on familiar families and close associates, as well as being able to identify strangers and being more cautious when interacting with these unknown individuals," who might act aggressively and pose a threat to the family unit.

Unknown elephants are not the only threats these pachyderms need to keep in mind to survive. Shannon was a co-author of a 2011 study in the journal Proceedings of the Royal Society B: Biological Sciences that demonstrated that younger elephants underreact to recorded sounds of roaring male lions, whereas older elephants (who would remember prior lion attacks) assume defensive positions in response to the roars. 

In another study, published in the journal Proceedings of the National Academy of Sciences in 2014, Shannon and colleagues demonstrated that elephants can also identify the voices of humans who pose a threat. They found that elephants are more likely to take precautions when they hear the recorded voices of semi-nomadic Maasai people, who periodically kill elephants, than the voices of other Kenyan ethnicities. The elephants were also more likely to defend themselves when they heard the recorded voices of Maasai men, as opposed to recordings of Maasai women and children. "The incredible memories and cognitive abilities of elephants has even enabled them to use human language to determine the threat posed by different groups of humans," he said.

Elephants' unique brain structures may be what allows them to pull off these impressive feats of memory and cognition. A series of studies conducted by Bob Jacobs, a professor of psychology who specializes in neuroscience at Colorado College, has demonstrated that elephants' cortical neurons are radically different from those of other intelligent species. Jacobs thinks that the unique characteristics of these neurons suggest that elephants carefully mull over their memories. "In terms of cognition," he wrote in The Conversation, "my colleagues and I believe that the integrative cortical circuitry in the elephant supports the idea that they are essentially contemplative animals."

Related: Why can't we remember our dreams?

Elephants also have the largest absolute brain size among land mammals, and the largest temporal lobe relative to body size; the temporal lobe is the part of the brain responsible for processing sounds and encoding memory.

The fact that elephants rely so heavily on their memory makes conservation efforts all the more necessary. When poachers target the largest elephants with the biggest tusks, they are usually placing the oldest elephants in their sights — repositories of the herd's collective memory — and those losses mean that younger elephants are left in charge of a herd that they do not have the experience to lead to safety during the dry season. 

Likewise, if elephant survival hinges on elders remembering migration routes, development that changes the landscape and cuts off crucial paths could have devastating consequences for entire herds. "Their habitat is threatened by human development blocking important migration routes, leaving them confined to marginal lands that often don't have important resources needed to survive long dry seasons," O'Connell said. "An obvious implication is the importance of preserving critical migration routes."

Memory is one of the building blocks of the brain. It can help keep us safe — that red stove burner is hot, don't touch it! — and forms the basis of our identities and narratives about our lives.

So how does the brain store memories and retrieve them?

The simplest answer is that the human brain reshapes itself with each new memory. This happens through the actions of synapses, or the tiny gaps between brain cells. Brain cells, or neurons, communicate with each other through an elegant electrochemical system. A change in the electrical charge of one cell triggers the release of chemicals called neurotransmitters across synapses. The neurotransmitters are then taken up by the neuron on the other side of the gap, where they trigger electrical changes in that cell.

"Ultimately, memories are encoded in circuits, and the synapses are just a means for etching out these circuits," said Don Arnold, a neuroscientist at the University of Southern California. "That's what changes in the brain when a memory is made, you have this new circuit that encodes the memory."

When one neuron continually stimulates another, their connection strengthens, meaning it becomes easier and easier for them to stimulate each other as time goes on. When they rarely communicate, their bond weakens, and sometimes they stop communicating altogether. At the most basic level, the brain can store memories by strengthening the connections between networks of neurons.

Where are memories stored in the brain? 

Human memories are stored in several brain regions. The most important is the hippocampus, which is actually a pair of regions tucked deep in the brain and curled into themselves like seahorses. These paired regions are important for initial memory formation and play a key role in the transfer of memories from short-term storage to long-term storage.

Short-term memory lasts for just 20 or 30 seconds before fading away. For example, you might remember a new phone number for the time it takes to dial it, but unless you rehearse the number again and again, the neural circuits that formed that short-term memory will stop activating together, and the memory will fade away.

When you rehearse information or try to remember it, the hippocampus kicks in to strengthen the circuits. Over time, longer-term memories are transferred to the neocortex, the outer wrinkly part of the brain that is responsible for much of our conscious experience. (Though because nothing in the brain is simple, a 2017 study published in the journal Science found that some remnants of these long-term memories also stay in the hippocampus.)

The amygdala, an almond-shaped region of the human brain that helps process emotions such as fear, also plays a role in memory. In a study published in March in the journal Proceedings of the National Academy of Sciences, Arnold and colleagues the researchers found that when fish learned to associate the light with a painful sensation, they developed new synapses in one part of a brain region called the pallium, and lost synapses in another part of the pallium. The pallium is similar to the amygdala, and the part of the fish pallium where the synapses strengthened in the study is full of neurons involved in processing painful stimuli, while the fish lost synapses among neurons that process positive or neutral stimuli, Arnold said. 

Emotion is an important component of memory-making, said Avishek Adhikari, a neuroscientist at the University of California, Los Angeles. Both positive and negative emotional situations are better-remembered than neutral events, likely for reasons of survival: It's probably important to remember things that were either very good for you, or very bad. 

The brain releases higher concentrations of certain neurotransmitters in high-emotion scenarios, Adhikari told Live Science, and the presence of these neurotransmitters can strengthen the memory circuits in the hippocampus.

Other regions involved in memory are the basal ganglia and cerebellum, which handle the motor memory needed to, for instance, play a piano piece, and the prefrontal cortex, which helps with “working memory,” which is involved when you need to hold information in your head long enough to manipulate it, for instance when solving a math problem, according to the University of Queensland.

The mysteries of memory 

The formation of new neurons also plays an important role in memory storage, even in adult brains. Scientists used to think that the brain stopped producing new neurons after adolescence, but research in the past two decades has shown that not only do adult brains make new neurons, but these neurons are key for learning and memory. A 2019 study in the journal Cell Stem Cell found that the hippocampus continues to generate new neurons even in people who are in their 80s and 90s. 

It's hard to observe memory formation and processing in a working brain. Synapses are tiny and numerous (there are around a trillion in an adult human’s brain), and it's hard to do imaging beyond the brain surface, Arnold told Live Science. Imaging methods also need to be able to avoid interfering with the brain's function. New technology is enabling new discoveries, though. For instance, to peer into the zebrafish brain while it learns to associate a flashing light with an unpleasant sensation, Arnold and his colleagues alter the fish genome so that it displays fluorescent proteins on its synapses. The researchers can then use a specialized microscope to take images of these synapses and monitor them for change.

Understanding how memory works is important for moving toward treatment of diseases like Alzheimer's, which causes memory loss. Understanding some of the quirks of memory can also help improve memory. For example, the hippocampus is not only involved in cementing memory, but in navigating places – which makes sense, given the importance of remembering where you are and where you've been when trying to get around.. People who achieve astounding feats of memorization, like remembering pi to tens of thousands of digits, often borrow the hippocampus' spatial memory abilities to do so. They'll mentally associate each item they want to remember with a location in an imaginary place — a trick called a memory palace. By picturing this place in their mind, a person practiced in this technique can recall large amounts of information.

"It's a very weird thing to do," Adhikari said, "but the reason that works is because the hippocampus is particularly good at and prone to mapping spatial routes." Originally published on Live Science.

Originally published on Live Science.

The "secret code" the brain uses to create a key type of memory has finally been cracked. 

This type of memory, called working memory, is what allows people to temporarily hold on to and manipulate information for short periods of time. You use working memory, for example, when you look up a phone number and then briefly remember the sequence of digits in order to dial, or when you ask a friend for directions to a restaurant and then keep track of the turns as you drive there.

The new work represents a "fundamental step forward" in the study of working memory, Derek Nee, an assistant professor of psychology and neuroscience at Florida State University, told Live Science in an email.

A critical process 

For decades, scientists have wondered how and where the brain encodes transient memories. 

One theory suggests that working memory relies on special "storehouses" in the brain, separate from where the brain handles incoming sensory information from the eyes or nose, for instance, or where long-term memories — like memories of who you attended prom with, or foundational knowledge you learned in school — are stored, said Nee, who was not involved in the new study. 

Another, opposing theory suggests that "there are no such special storehouses," Nee told Live Science. In this alternate theory, working memory is essentially an emergent phenomenon — one that shows up "when sensory and motor representations are kept around as we link the past to the future," Nee said. According to this theory, the same brain cells light up when you first read through a phone number as do when you run through that number again and again in working memory.

Related: Your brain exaggerates memories to remember them better 

The new study, published April 7 in the journal Neuron, challenges both of these theories. Rather than reflecting what happens during perception or relying on special memory storehouses, working memory seems to operate one step up from sensory information gathering; it extracts only the most relevant sensory information from the environment and then sums up that information in a relatively simple code. 

"There have been clues for decades that what we store in [working memory] might be different from what we perceive," study senior author Clayton Curtis, a professor of psychology and neural science at New York University (NYU), told Live Science in an email. 

To solve the mysteries of working memory, Curtis and co-author Yuna Kwak, a doctoral student at NYU, used a brain scanning technique called functional magnetic resonance imaging (fMRI), which measures changes in blood flow to different parts of the brain. Active brain cells require more energy and oxygen, so fMRI provides an indirect measure of brain cell activity.

The team used this technique to scan the brains of nine volunteers while they performed a task that engaged their working memory; the two study authors also completed the task and contributed brain scans to the study. 

In one of the trials, the participants viewed a circle composed of gratings, or slashes, on a screen for roughly four seconds; the graphic then disappeared, and 12 seconds later, the participants were asked to recall the angle of the slashes. In other trials, the participants viewed a cloud of moving dots that all shifted in the same direction, and they were asked to recall the exact angle of the dot cloud's motion.  

"We predicted that participants would recode the complex stimulus" — the angled grating or moving dots — "into something more simple and relevant to the task at hand," Curtis told Live Science. Participants were only asked to pay attention to the orientation of the slashes or angle of the dot cloud's motion, so the researchers theorized that their brain activity would reflect only those specific attributes of the graphics. 

And when the team analyzed the brain scan data, that's just what they found.

Related: Sherlock Holmes' famous memory trick really works 

The researchers used computer modeling to visualize the complex brain activity, creating a kind of topographical map representing peaks and valleys of activity in different groups of brain cells. Brain cells that process visual data have a specific "receptive field," meaning they activate in response to stimuli that appear in a particular zone of a person's visual field. The team took these receptive fields into account in their models, which helped them understand how the participants' brain activity related to what they'd observed on-screen during the memory task.  

This analysis revealed that, instead of encoding all of the fine details of each graphic, the brain stored only the relevant information needed for the task at hand. When viewed on the topographical maps, the brain activity used to encode this information looked like a simple, straight line. The angle of the line would match the orientation of the gratings or the angle of the dot cloud's motion, depending on which graphic the participants had been shown.

These line-like brain activity patterns appeared in the visual cortex, where the brain receives and processes visual information, and the parietal cortex, a key region for memory processing and storage. 

What's crucial isn't that the brain settled on using lines to represent the images. "It is the fact that the representation has been abstracted from gratings [or] motion to something different," Nee said. 

One limitation of the study is that the team used very simplistic graphics, which don't necessarily reflect the visual complexity of the real world, Nee noted. This limitation extends to many studies of working memory, and Nee said he uses similar simple graphics in his own research.

"The field will need to move towards richer stimuli that better match our natural visual experiences to bring us from the laboratory to practical utility," he said. But with that in mind, the new study still "provides a novel insight into what it means to hold something online in mind for the future," he said. 

Working memory essentially acts as a bridge between perception (when we read a phone number) and action (when we dial that number). "This study, in identifying a representational format that resembles neither what was perceived nor what will be done but can be clearly read out from visual signals, offers an unprecedented look into this mysterious intermediate zone between perception and action," Nee said.

Originally published on Live Science. 

Nobody's memory is perfect. For instance, do you think that Stouffer's Stove Top Stuffing existed? Or that there was a children's book series called "The Berenstein Bears?"

In reality, neither of these references are spot-on. Stouffer's never made a stove top stuffing, and the books are actually known as "The Berenstain Bears." But if you got these details wrong, don't feel too bad — a 2020 memory study in the journal Psychological Science found that, when asked to recall information, 76% of adults made at least one detectable error.

Although the memory accuracy of the study’s participants was generally "very high," with around "93-95% of all verifiable details" being correct, the research highlights that a person’s memory is not infallible. Things that never happened, or events that have become muddled over time, can, in one's head, become real, and knowledge can become distorted or confused.

This is the foundation of the "Mandela effect."

Related: Does subliminal messaging really work?

The Mandela effect is when many people believe that something happened when, in reality, it never did. These groups are adamant that they can remember an incident or specific experience, even when it is demonstrably incorrect. 

The name refers to a mass false memory involving numerous people admitting to remembering Nelson Mandela dying in prison during the 1980s. In fact, Nelson Mandela died at his home in 2013.

The term was coined by Fiona Broome, a self-proclaimed "paranormal consultant," after she became aware that other people shared her recollection of Mandela dying while incarcerated.

The Mandela effect is now used to describe a collective false memory that, though false, has become real in the minds of many. 

Generally, these memories are based in popular culture. Two of the most widely recognized examples involve people misremembering the color of a packet of a particular flavor of snack, or believing that the show "Looney Tunes" was actually called "Looney Toons." 

So, why does this happen? Why is it that people who have never met can share the same misconception?

"The Mandela effect seems to be closely related to a number of well-known memory phenomena," said Tim Hollins, a professor of experimental psychology at the University of Plymouth in the U.K.

Hollins named three similar types of memory-related phenomena: "false memory," which is the creation of a memory that didn't happen; "source-memory errors," which is when someone forgets the true source of a memory; and "imagination inflation," which is the tendency to believe something is real the more often, or the more vividly, it is imagined.

Hollins also pointed to a several social elements as examples of how fallible our memories can be, such as the "Asch conformity," which is when people conform to a view in order to fit in with a group, and the "misinformation effect," which describes a tendency for people's memories to alter based on subsequent learnings or experiences.

However, Hollins believes the phenomenon that most closely aligns to the Mandela effect is that of "gist memory," which is when someone has a general idea of something but can't necessarily remember the specifics. 

"It is relatively easy to explain how many people could come to the same errors of memory, even if entirely independently," Hollins told Live Science. "For instance, many appear to be 'gist memories' adapted to fit people's existing beliefs or knowledge."

A common example of the Mandela effect relates to "Curious George," a children’s book character that first appeared in the 1940s, and his lack of a tail.

"Remembering Curious George as having a tail just reflects the fact that most monkeys have tails," Hollins said. "If you just remember the gist — it's a monkey — why wouldn't you remember him having a tail?"

Related: Why do chimpanzees throw poop?

However, while various explanations for the effect exist, and though there is evidence that our memories are not entirely accurate and can alter over time, some who have experienced the Mandela effect are convinced it is actually evidence of the existence of parallel universes. 

Hollins believes this is a case of certain people being unwilling to admit when they are wrong.

"People do tend to over-believe their own memories, even when faced with the evidence," Hollins said. "Perhaps it's a form of ego-protection or cognitive dissonance." 

Hollins said that people choose to believe their mistaken memory is evidence of parallel universes to  "explain" how they can simultaneously consider themselves to have a strong memory, while being confronted with evidence to the contrary. 

So, is there any chance that the Mandela effect could be evidence of parallel universes? 

"No. It's nonsense," Hollins concluded. 

Originally published on Live Science.

What happens in your brain when you recognize your grandmother? In the 1960s, some neuroscientists thought a single brain cell called the "grandmother neuron" would light up only at the sight of your grandmother's face. Almost immediately, neuroscientists began to dismiss the theory — a single neuron could not correspond to one idea or person, they argued. 

More than 50 years later, new research in monkeys shows that "grandmother neurons" may exist after all. In a study published on July 1 in the journal Science, researchers found a small area of the monkey brain that responds only to familiar faces. Up to three times as many brain cells in this area responded to familiar faces than to unfamiliar ones. The study follows research showing that certain parts of the human brain respond to specific categories, including one region primarily dedicated to faces. One study even found that individual neurons in different parts of the brain responded only to specific celebrities and landmarks. But few studies had found any part of the brain that reacts specifically to personally familiar faces. 

Though the new research did not identify individual cells devoted to a single person, the brain cells the researchers found share some crucial qualities with the theorized "grandmother neuron."

"In some sense, you can say they are grandmother neurons," said Winrich Freiwald, a professor of neuroscience and behavior at The Rockefeller University in New York City, who led the new research. "They have this unique combination of vision and memory."

The researchers examined the temporal pole, a poorly understood area near the bottom of the brain that Freiwald and lead study author Sofía Landi, a postdoctoral fellow at the University of Washington in Seattle, had identified as one of two areas that might be involved in familiar face recognition in a study published in 2017 in the journal Science. (The previous research was completed while Landi was a doctoral student in Freiwald's lab.) 

For the new study, the researchers used functional magnetic resonance imaging (fMRI) to scan the brains of two rhesus monkeys while they looked at images of monkey and human faces mixed with some other images. The brain scans served as a guide so the researchers could place electrodes in two areas of the monkey's brains — one in the temporal pole and one in another area of the brain that responds to faces in general but that past research suggested would not necessarily distinguish between familiar and unfamiliar ones. 

These electrodes enabled the researchers to monitor the activity of individual brain cells in the two areas. Brain cells in both areas lit up when the monkeys were shown images of monkey and human faces. But only the temporal pole cells distinguished between personally familiar and unfamiliar ones: When the monkeys saw photos of their pals and relatives, those temporal pole cells lit up three times more than when unfamiliar monkey photos were shown. These neurons barely responded to other faces, including both familiar and unfamiliar human faces as well as unfamiliar monkey faces. 

The discovery goes against prevailing wisdom in neuroscience. Generally, scientists believe that diverse areas of the brain must communicate with each other to process information. But this research indicates that "it's one area, this region, and it's there for this one purpose — recognizing people we know," Freiwald said. "That's amazing." 

The researchers also obscured the images of faces to varying degrees to see how the brain responses might differ. In the generic face-processing area, more cells gradually responded to the images as it became clearer and clearer that they were faces.But the response from temporal pole cells was different. They responded very little to highly blurred images, but as soon as the clarity reached a certain threshold, many of the neurons responded all at once to familiar faces. The researchers think this effect corresponds to the "a-ha" moment of recognition of a familiar face, say of your grandmother. 

When the researchers measured how fast the cells responded, they were surprised to find that there wasn't much difference between the two areas. The general face-processing area, which seems to engage only if an image is a face, responded to faces in about the same time as cells in the temporal pole area responded to only familiar faces. That is "very, very surprising," said Freiwald, because the assumption was that the grandmother neurons would take longer, since the person would first have to identify the image as a face, then associate it with a long-term memory of a specific person. 

The new research, though in many ways groundbreaking, comes with limitations. It was done on monkeys, not humans, and only on two individuals. However, Freiwald notes that rhesus monkeys, as highly social primates, are the best animal models to use for a study like this and are thought to have very similar face-recognition processing to humans. 

The researchers also don't know how exactly face information is being sent to this temporal pole region. The temporal pole doesn't directly process vision or store long-term memory, and because there aren't known pathways between the temporal pole and these other parts of the brain, the route that information might take to get there is still unknown. 

The insight could eventually help people who can't recognize others, said Freiwald. For instance, people with dementia and those born with prosopagnosia, or "face blindness," sometimes can't recognize close friends or even family members, something Freiwald imagines is "crushing."

Freiwald also noted that recognizing a person isn't a purely visual, or even sensory, experience. "There's also almost an emotional quality to it, like 'Huh, I know this person,'" he said. "That is ignited, we think, by this area, but there must be so much more involved in it."

Originally published on Live Science.

An ancient memory technique developed by Aboriginal Australians may work better than the "mind palace" invented in ancient Greece and popularized by the BBC version of Sherlock Holmes.

Both methods involve mentally attaching information to a physical object or location, but the Aboriginal technique adds a storytelling component. Researchers aren't sure if it's the narrative element or some other aspect that seemed to boost the Aboriginal technique's effectiveness, and the study is small. But the research highlights that cultures put in a lot of effort in order to pass along information without modern-day technology or even writing.

Related: 6 fun ways to sharpen your memory

"There's a certain satisfaction in knowing how to learn these things," said study co-author David Reser, a lecturer at the Monash University School of Rural Health in Australia.

Building memories 

The "mind palace" is a method of remembering that attaches information to objects inside an imaginary building or room; also known as the method of loci, the technique is said to have originated when the Greek poet Simonides of Ceos narrowly avoided being crushed in a building collapse during a crowded banquet. Simonides was able to identify the bodies of his fellow revelers by remembering where they'd been sitting before he stepped out of the room, illustrating the value of attaching memories to a physical location — even if just in the mind. The character of Holmes uses the technique to help him crack cases in the BBC series "Sherlock," which aired between 2010 and 2017. Research on the mind palace technique shows that it boosts both short- and long-term memory.

A new study tests the mind palace technique against the one used by untold generations of Aborigines. This technique also attaches information to physical geography, but in the form of a narrative that incorporates landmarks, flora and fauna. The idea to compare the two arose when Reser and a fellow lecturer, Tyson Yunkaporta, were chatting about memory and ways to incorporate Indigenous culture into the medical school curriculum. Yunkaporta, now at Deakin University in Victoria, Australia, is a member of the Apalech Clan and author of "Sand Talk: How Indigenous Thinking Can Save the World" (HarperOne, 2020).

Along with other colleagues and medical students, Yunkaporta and Reser put together a study of the two techniques, drawing from first-year medical students at the university during their very first days of classes. Seventy-six students participated. They were first shown a list of 20 common butterfly names — chosen specifically because the researchers wanted the study to have nothing to do with medicine — and given 10 minutes to memorize the list. They were then told to write down as many of the names as they could remember.

Next came a 30-minute session during which a third of the students were taught the "memory palace" technique, and a third were taken to a garden on campus, where Yunkaporta walked them through the Aboriginal technique and developed a story attached to the garden for memorizing the butterfly list. The final third, a control group, watched an unrelated video during this time.

The students were again given the list and 10 minutes to memorize; then they were asked to write down the butterfly names again. After a 20-minute unstructured break, they were tested for a third and final time.

Incorporating a narrative 

All of the students improved over the tests, simply because they had seen the list several times. The memory palace technique improved the total percentage of the 20 names that the students remembered by a moderate amount, with the Aboriginal technique showing a strong effect. This translated to only one or two extra names, though, as the test turned out to be a little too easy for the eager medical students — many remembered 20 out of 20 butterfly names on the first try, without any training at all, Reser said. A future study with medical school students would need to be more challenging, he said.

"By the time someone gets into medical school they probably have developed some pretty sophisticated techniques themselves," he said. 

However, other ways of looking at the memory training also showed improvements with the Aboriginal technique compared to the mind palace. The chances that a student would improve from remembering fewer than 20 of the names to 20 out of 20 on later tests tripled in the Aboriginal group, doubled in the mind palace group, and went up only by 50% in the untrained group. The students trained in the Aboriginal technique were also significantly more likely to list the butterfly names in order than the other two groups. The test didn't require ordering the list, Reser said, but it makes sense that students who were attaching the information to a narrative would remember the information in a certain sequence.

"You can envision, certainly, in the medical field things where order is important," Reser said. "If you're remembering, say, a biochemical pathway or a surgical technique."

The advantage of the Aboriginal technique may have been due to the additional layer of the narrative, Reser said. Or it could have had something to do with the fact that participants physically went to the garden to learn (the mind palace participants simply imagined their childhood homes). The storytelling of the Aboriginal technique was also communal instead of individual, which could have also helped boost memory.

Not enough students returned for a follow-up for the researchers to test the long-term impacts of the different training methods. Study co-author Magaret Simmons, a senior lecturer at the medical school, did gather feedback from the students after the study and found that they enjoyed learning the techniques and that some still used them in their studies.

That was promising, Reser said, as many medical students feel anxious about the amount of memorization they're expected to do. He and his colleagues would like to incorporate these methods into the curriculum, he said, but it's important that they find an Aboriginal instructor who can accurately and sensitively convey the technique. In Aboriginal practice, the method is quite complex, Reser said, with multiple layers of information conveyed through song, stories and art. It also takes hard work and practice to keep the information attached to the narratives fresh.

"We want students to have exposure to Aboriginal culture and to be aware of just how rich and how deep into history this goes," he said.

The findings were published May 18 in the journal PLOS One. 

Originally published on Live Science.

Goldfish are known for their orange hues and terrible memories. One common saying even claims that these creatures have a mere 3-second recall.

However, this is a complete myth that, despite its lack of scientific backing, has spread widely and remained largely undisputed by the public for decades.

"What is baffling is that it's pretty much the same wherever you go in the world," Culum Brown, an expert in fish cognition at Macquarie University in Australia, told Live Science. "In some places, it's 2 seconds, and in others, it's 10 — but it's always short."

Related: Which animal has the stretchiest mouth?

In reality, goldfish (Carassius auratus) have much longer memories — spanning weeks, months and even years, Brown said. And the science to back this up has been around for more than 60 years.

"We've known about the reasonably good memories of goldfish since the '50s and '60s," Brown said. "Despite what everybody thinks, they're actually really intelligent."

Brown has studied the intelligence of fish, including goldfish, for more than 25 years and thinks the misconception comes from a combination of ignorance about fish intelligence in general and guilt, because pet owners often keep them in small, boring tanks.

Goldfish intelligence

In reality, goldfish have such impressive memories, they're often used as a common model for studying memory and learning in fishes, Brown said. As a result, "there are thousands of studies [on goldfish] that show fish have excellent memories," Brown said. "And the rate of which these studies are being published is growing exponentially."

A majority of these studies involve food. For example, if goldfish are fed at only one side of their tank, they will quickly learn and remember to stay on that side of the tank at feeding times, regardless of whether they are actually fed, Brown said. Similarly, if pushing a red paddle gains a food reward but a blue one doesn't, goldfish quickly learn to push the red and not the blue, and will continue to show a preference for that color long after the experiment is finished. These types of experiments have also been replicated with other cues, such as bubbles and even music, Brown said.

Goldfish are also good problem-solvers and have been taught to escape nets and navigate mazes, Brown said. They can even remember how to repeat these tasks weeks, and even months, later, Brown said.

Other evidence suggests that goldfish can recognize and remember other individuals, even after long periods of separation, Brown said.

On top of these findings, there is a wealth of anecdotal evidence from goldfish owners who often observe complex behaviors in their pets when interacting with them. Some even claim that their goldfish can recognise them apart from other people.   

It is hard to pinpoint an exact time span for goldfish memory, given that different memories are more notable than others. You're more likely to remember a scary event, for instance, than a mundane one, Brown said. But whether goldfish memories last days, weeks, months or years, it's safe to say they definitely last longer than 3 seconds.

Related: Can you recover repressed memories? 

Public perception 

Despite reams of research, the public's view on goldfish memory hasn't budged much. A big reason for this is that "fish have a serious PR issue," Brown said.

Most people do not come across live fish in their daily lives, and even when they do, "people don't interact with fishes the way that they do [with] other animals," Brown said. This makes it easier for misconceptions and myths to be widely accepted, he said. Public perception of fish cognition may be improving, however, as more wildlife charities and nongovernmental organizations spread the word about fish intelligence. "It's changing more rapidly now than it was than it has done in the past," Brown said. "But it's still slow."

Guilt from pet owners may be another factor in understating goldfish memory. "I suspect it's got more to do with making us feel good about putting them in a tiny little bowl," Brown said. "It probably says more about us than it does about the goldfish."

Properly cared for goldfish can live 20 years, so owners might want to consider getting their pets large tanks with enrichment objects and companion fish, as well as taking the time to play games with them and teach them tricks, Brown said. After all, your goldfish might remember certain experiences for years to come.

Originally published on Live Science.

Like a fisherman talking about the size of the one that got away, the brain exaggerates its memories. 

This exaggeration is in the service of good, however. New research finds that when people exaggerate the differences between similar memories, they recall them better. The findings could help explain why memory works, and why it often declines with age. 

The research involved asking people to match faces to objects, which often differed only slightly in color. When people mentally exaggerated the color differences between the objects, they were better at recalling which face went with which object. Brain imaging showed that this exaggeration was tied to activity in a region of the brain called the lateral parietal cortex. 

"It's very fascinating to me to see that memory distortions can actually help us to tell these similar memories apart," said Yufei Zhao, the lead author of the study and a doctoral student in psychology at the University of Oregon. 

Making memories 

Zhao and her colleagues had previously conducted research on the hippocampus, a curved region deep in the brain that sits above the brainstem and is important for initially encoding memories. Brain imaging studies had shown some differences in how the hippocampus handled memories of two very similar events, but it wasn't clear whether there were any changes to the content of the memory itself. 

In the new study, published in the Journal of Neuroscience on Feb. 22, Zhao and her co-authors focused on a part of the brain that doesn't encode memories but rather helps to recall them: the lateral parietal cortex, which sits beneath the top back of the skull.

"Parietal cortex is actually the place where the memory is housed when we retrieve our memory," Zhao told Live Science. "You will hold your memory in your parietal cortex, so investigating the parietal cortex can give us a very nice window to look at the details of our memory."

There were 29 participants in the study. On day one of the study, the participants were shown 24 different faces, each associated with a different everyday object, such as a beanbag, hat, balloon or umbrella. Unbeknownst to the participants, the researchers had chosen the objects so that they could later be paired up in a recall test. In half of the cases, these pairs were made up of two different objects — a balloon and a hat, perhaps — that were subtly different in color, just 24 degrees apart on a color wheel. In the other half of cases, the pairs were made up of the same objects — two beanbags — only different because their shades were also 24 degrees apart on the color wheel. One might be light green and the other darker green, for example. 

Exaggerated differences 

Two beanbags of slightly different color shades should be harder for the brain to remember than a balloon and a hat in those same shades, the researchers reasoned. Thus, if the brain distorts memories to remember them better, the participants should have exaggerated the gap between the colors of same-object pairs more than the gap between the colors of different-object pairs. 

On day two of the study, the participants tested their recall. They were shown a picture of a face and the object associated with that face in grayscale. They then had to pick the color of the object on a color wheel. Sure enough, the participants exaggerated the gap in colors in the same-image condition but did not do so in the different-image condition. 

This exaggeration was also associated with accuracy, the researchers found. The participants were better at remembering which face went with the correctly colored object when they exaggerated the color differences between the same-object pairs. 

Then, the study authors tracked brain activity using  functional magnetic resonance imaging (fMRI), which detects changes in oxygenation correlated with blood flow within the brain. Areas with more blood flow are more active. The researchers found differences in the patterns of activation in a wrinkle in the parietal cortex called the ventral intraparietal sulcus. These differences were focused in a region that encodes information about shape and color, and were more pronounced when the participants were recalling same-object pairs versus different-object pairs, meaning that the differences correlated with the exaggerations in the color gaps in people's memories. 

"The neural pattern actually remembers them as less similar to each other, Zhao said. That dissimilarity is then correlated with better memory performance, she added.

Similar memories interfere with each other, becoming difficult to recall clearly (for example, it's easier to remember the one time you parked your car at Disneyland than one of the hundreds of times you parked at your office parking garage). The finding explains one way the brain reduces interference between similar memories, she said. Most likely, she said, this interference reduction starts in the hippocampus, where the brain may initially weigh the differences between two memories heavily in order to differentiate them. For example, if you went to the beach on two different days but one day was windy and the other was calm, the hippocampus might make special note of the weather difference when encoding the memory. Then, when you recall the memory, the parietal cortex may exaggerate the windiness of one day and the stillness of the other so that you retrieve the right day. 

The participants in the study were all young, healthy adults with good memory recall, Zhao said — they were 98.9% accurate at recalling face-object matches when the objects were different and 93.2% accurate at remembering the matches when the objects were the same. The next step, she said, is to study older adults. Memory performance declines with age, Zhao said, and one reason might be that the brain becomes less skilled at reducing interference between memories. The researchers now want to find out if the brains of older adults fail to exaggerate the differences between their similar memories. 

Originally published on Live Science.

Sherlock Holmes remembers everything by imagining that he's storing bits of information in a "memory palace," a technique that originated in ancient Greece. Now, researchers have found that this method really does work to create long-lasting memories.

Users of the mnemonic technique, called the "method of loci," mentally navigate around a familiar place, such as a path (or Holmes' palace). To remember a piece of information, you "drop" it along the path and later retrace your steps and "pick it up." For example, if you're very familiar with Central Park in New York City, you can imagine walking through it, dropping the word "book" at the Boat House, then the word "water bottle" at the next bend, then the word "space" at the fountain. When you want to remember the words, you imagine retracing your exact steps.

By training with this method, the world's best memory champions can remember inordinate amounts of information, like word lists, digit series and decks of cards, according to the study. But the World Memory Championships test only short-term memory and only a handful of studies have looked into the brain as people use this method to improve memory.

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"We became fascinated by how such extraordinary memory performance as shown in the World Memory Championships is possible," said lead author Isabella Wagner, a cognitive neuroscientist at the University of Vienna. (One of the study co-authors, Boris Konrad — a researcher at the Donders Institute for Brain, Cognition and Behaviour in Nijmegen, Netherlands — is a memory champion himself.) 

The method of the loci uses well-known places or routes as a "scaffold" or "structure" to embed novel, unrelated information, Wagner said. The combination of prior knowledge — the familiar route — and the novel information "is very powerful to boost memory," she added.

To evaluate the method of loci, Wagner and her team enrolled 17 "memory athletes," or champions who were ranked among the world's top 50 in memory competitions, and 16 others that matched the athletes in characteristics such as age and intelligence. The researchers took functional magnetic resonance imaging (fMRI) scans of the participants' brains while asking them to study random words on a list. Then, the researchers presented the participants with three words at a time from the list and asked them to recall if the words were in the same order as previously studied. 

In the second part of the study, they enrolled 50 participants who previously had no experience in mnemonics and trained 17 of them for six weeks to recall memories using the method of loci. The rest of the participants were in the control group (16 of them were "active controls" which meant they were trained using a different memory tactic called "working memory training," and 17 were "passive controls," meaning they weren't trained at all). They again scanned the participants' brains with fMRI as they performed the same tasks, both before and after training. The researchers also asked the participants to recall which words were on the list 20 minutes and 24 hours after their fMRI scans.

The team used this test to define "weak memories," or those that could be remembered after 20 minutes but not after 24 hours, and "durable memories," or those that could be remembered 24 hours later. Four months later, the researchers retested the participants' ability to memorize and recall words.

Better memory

As expected, the participants showed better, longer-lasting memory after training with the method of loci than after training with the other memory technique or with no technique at all. The participants who trained with the ancient method showed a significant increase in durable memories, but not a significant change in weak memories (or short-term memories that faded after 20 minutes), compared with the control groups.

After 20 minutes, the people who were trained with the method of loci remembered about 62 words from the list, whereas those who were trained with the other method remembered 41 and those who weren't trained at all remembered 36. After 24 hours, the people who were trained with the method of loci remembered about 56 words, versus 30 and 21 in the control groups, respectively.

Four months later, people who were trained with the method of the loci could remember about 50 words, versus 30 and 27 in the control groups, respectively. What's more, world memory champions and the participants who trained with the method of loci showed similar brain activity as they memorized word lists and ordering.

The team also came across something unexpected: While both the world champions and the  participants were partaking in these tasks, activity in their brains declined in regions typically involved in memory processing and long-term memory, Wagner told Live Science in an email. "This was somewhat surprising to us, as better performance is typically associated with increased engagement of different brain regions," she said.

In other words, they found that less brain activation led to better memory, which may be because the method of loci prompts the brain to work more efficiently, Wagner said. In addition, while the participants rested, those who had been trained with the method of loci had increases in brain connectivity between other reasons important for storing long-term memory.

Almost anyone can learn to use the method of the loci, Wagner said. "It obviously requires time and regular practice and might thus not be suited for everyone, but it is definitely possible to 'boost' memory and reach high, or even exceptional, memory performance." 

The researchers didn't test how this training might generalize to other situations, such as remembering things other than words. Nor is it clear if the technique might help to ease cognitive decline during healthy aging or if it might be helpful for preventing or slowing disease, Wagner said. "However, we are quite excited about these results, and a whole avenue of new questions opens up that should give future studies ample material to investigate," she said. 

The findings were published Wednesday (March 3) in the journal Science Advances.

Originally published on Live Science.

A neon-yellow slime mold can store memories, even though it lacks a nervous system. Now, scientists have found a new clue as to how the brainless blob manages this impressive feat.

The single-cell organism, known as Physarum polycephalum, belongs to the taxonomic group Amoebozoa, the same group as amoebas, Live Science previously reported. The blobs can exist as one tiny cell with one nucleus, the cell's control center, or multiple cells can fuse together to form one gargantuan cell with many nuclei. These fused cells can grow to cover dozens of square inches (hundreds of square centimeters) in area. 

When fused, the huge cells form a complex network of internal tubing; these tubes contract, similar to blood vessels, to push fluid and nutrients through the brainless blob.

The new study, published Feb. 22 in the journal Proceedings of the National Academy of Sciences, shows that the diameters of these branching tubes can encode information, such as where the slime mold has recently found food. When the blob finds food, it rapidly reorganizes its tubular network, widening some tubes and shrinking others, and this architecture remains in place even after the blobs have eaten the food.

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This basic form of memory may help slime molds solve complex puzzles, such as finding the fastest route to food or the shortest path through a maze, senior author Karen Alim, an associate professor of biological physics at the Technical University of Munich, told Live Science in an email. 

When P. polycephalum senses a snack nearby, by detecting chemicals that its food lets off, the tubes nearest to the food begin to dilate. Meanwhile, tubes farther from the food shrink and sometimes disappear altogether, becoming reabsorbed by the slime. The slime mold then creeps in the direction of the wide, dilated tubes, migrating until it engulfs its snack.      

But even after gobbling down every morsel of food, the slime mold hangs on to the cluster of thick tubes, leaving a long-lasting "imprint" of where the food was once located, the authors wrote. This dictates how fluid flows through the whole network and influences which direction the slime mold travels next. For instance, if more food crops up near the thick, imprinted tubes, the slime mold is already prepped to spread in that direction, and that imprinted "memory" becomes reinforced.

"In the brain, we store information by strengthening or weakening connections between individual neurons," a kind of nerve cell that sends electrical and chemical signals, Alim said. "Each additional impulse may strengthen an existing strong connection." 

A similar — but simplified — process shapes memory formation inside slime molds, she said. 

And just like connections in the brain, slime mold "memories'' can grow weaker if they're not reinforced, Alim added. While tubes near food grow thicker, tubes far from food grow thinner and may disappear. "Memories vanish when tubes retract and vanish" into the larger slime mold, Alim said. In this way, old memories of food can be overwritten as the blob migrates and hunts for new nutrients.

Past studies of slime molds also hinted that the "slime mold network adapts to external cues and that the network could be used as a read-out of what the slime mold experienced," said Audrey Dussutour, a researcher who studies cognitive processing in ants and slime molds at the University of Toulouse in France. The new study provides more evidence as to how and why the tubular network reorganizes, Dussutour, who was not involved in the research, told Live Science in an email.

"The results remind me of trail networks in ants," where foraging ants lay down a trail of chemicals for other ants to follow, Dussutour added. As more ants follow the same trail and deposit more chemicals, more ants become likely to follow the well-worn trail over another, less-traveled one, according to a 2005 report Dussutour co-authored in the journal Proceedings of the Royal Society B.

However, while scientists know what pheromones ants secrete to lay their trails, it's uncertain what signal tells tubes to widen and others to shrink, Alim said. 

Based on lab experiments and computer models of P. polycephalum, the authors suspect that the slime mold produces some soluble substance upon sensing food and that this substance causes the tubes closest to the food to soften and stretch. As the gel-like walls of the tubes stretch, some of the substance leaks into the larger network of tubes and becomes more diluted the farther it travels. Therefore, tubes far away from the food source receive very little of the substance, if any, the study authors explained.

While there's evidence that this mystery chemical drives the tube dilation, we sadly have no idea on its chemical composition," Alim said. That will be the focus of future research.

In addition, "the next step is to ask how many memories can be stored in a network and if we can transfer the mechanism to synthetic systems to build smart materials," Alim said. These smart materials would mimic the living flow networks found in slime molds and could be used to build soft-bodied robots, for example, according to a statement. 

Originally published on Live Science.

Throughout the late 1980s and early 1990s, the United States was in the grip of a panic. Thousands of adults were recovering memories of horrific childhood abuse — memories they believed they had long repressed because they were too painful to bear. In all, 736 legal claims were filed, usually against family members, based on these memories, according to The False Memory Syndrome Foundation, a non-profit based in Philadelphia.

At the end of the 1990s, the epidemic of recovered childhood traumas died down as investigations by the Federal Bureau of Investigation and Department of Justice proved some allegations of abuse false. But the concept of memory recovery never completely disappeared from psychology. A recent study found that 76% of clinicians still believe in memory repression today. 

But is it really possible to recover deeply repressed memories of an event, years after it happened?

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It was early 20th century psychologist Sigmund Freud who initially theorized that people dissociate, or tune out, at the time of a trauma, losing all memory and awareness of the event. But there's no evidence that such a mechanism is possible, said Albert Katz, a psychologist at Western University in Ontario, Canada.

"There's no doubt we can forget things," Katz told Live Science, "But that doesn't necessarily mean that there's been this active process to keep them out of consciousness."

There are many reasons people forget. We gradually forget the things we don't call to mind frequently. We also tend to forget mundane, everyday events. We can even forget on purpose, said Charles Brainerd, a psychologist at Cornell University. In one study, participants were more likely to forget a list of words when told to put it out of their minds. Although intentionally forgetting (also called "directed forgetting") might help you forget an awkward first date, it won't cause a real trauma to fade from memory. That's because we preferentially remember traumatic events, Brainerd said. "It's one of the basic laws of memory," he told Live Science.

There's a grain of truth in memory recovery, Katz said. It is possible for memories to return spontaneously to mind, years after an event, especially when triggered by a sight, smell or other environmental stimulus. But these memories aren't pristine. 

"Memory does not work like a tape recorder," Katz said, "Memory is very flexible, very fluid. So what we often remember are the nuggets of something. And then later on, we embellish." 

A number of therapies in vogue during the 80s and 90s aimed to bring so-called "repressed memories" to the surface. Therapists and their clients thumbed through photos of their childhood and read books in which characters were sexually abused, Brainerd said. They participated in hypnosis and guided imagery exercises, in which therapists give verbal suggestions to help clients call to mind specific scenarios and sensations. 

The problem was, these styles of therapy encourage people to develop “memories” that never actually happened, Katz said. That’s because people are prone to creating false memories when given hints or suggestions. For example, when shown doctored photos of themselves in hot air balloons, 50% of research participants in one study "remembered" riding on a flying contraption upon which they'd never even set foot. Similarly, books, photos and guided imagery primed people to "remember" abuse that had never happened, tk said.

Just like the study participants who envisioned themselves in hot air balloons, these clients believed the horrifying imagery they called to mind, as vivid as a real memory. 

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Originally published on Live Science.

People who are high on cannabis are more likely to form false memories, in which they wrongly "remember" information that they never actually learned or recall snippets of an event that never happened, new research suggests.

False memories can arise spontaneously when people draw faulty inferences from their actual experiences. For instance, you might remember your co-worker being at the big meeting last Monday because everyone else attended when, in reality, he was out sick. In other cases, external sources supply the misleading information that fuels false memories, whether in the form of leading questions, faulty personal accounts from other people or misinformed media coverage. 

Everyone occasionally crafts false memories, even when sober. But now, a study published Feb. 10 in the journal Proceedings of the National Academy of Sciences  suggests that cannabis use may raise the risk of forging false memories — a point that could prove critical in court. 

"The law has recognized that certain witnesses are vulnerable, so you need to take extra care" when questioning them, said co-author Elizabeth Loftus, a distinguished professor of psychological science and law at the University of California Irvine School of Law. Children and people with mental disabilities are considered "vulnerable" witnesses, for example. "Maybe cannabis-intoxicated witnesses should join that club," Loftus said. 

Two experts told Live Science that, while the effects of cannabis on memory should be taken seriously in court, more research is needed to determine when and how police should question intoxicated witnesses to obtain more reliable testimonies. 

Spontaneous confusion 

As cannabis use becomes more commonplace and widely accepted around the world, understanding how the drug affects memory will become critical to the way officials handle criminal cases, said lead author Lilian Kloft, a graduate student in the Department of Neuropsychology and Psychopharmacology at Maastricht University in the Netherlands.

"Cannabis is the most widely used drug worldwide, after legal substances such as alcohol and nicotine," Kloft told Live Science in an email. "There is a need to find out how this affects [witnesses'] memory, their reports, so that in turn evidence-based policies can be shaped." 

With this goal in mind, Kloft and her colleagues recruited 64 volunteers in the Netherlands to inhale a dose of vaporized cannabis and have their memory tested. The team designed the experiment to examine two kinds of false memories: those that arise somewhat spontaneously and those that external sources introduce. 

Related: 25 odd facts about marijuana 

To test spontaneous false memories, the team turned to a well-known experiment known as the Deese-Roediger-McDermott (DRM) Task. In that experiment, volunteers memorize a list of related words — such as "tired," "pillow," "bed" and "snore" — and then get tested on their recognition of those words. The catch is that, during the testing round, learned words get mixed in with new words that the volunteers weren't asked to memorize. In one experiment, the volunteers memorized a word list while high, and in another, they memorized a different list while sober. 

The new words ranged from totally unrelated to highly related to the words on the original list. Typically, people wrongly remember highly related words despite not having seen them before. 

Indeed, this was the case when the volunteers were tested immediately after the memorization round, whether they were high or sober. While intoxicated, however, the participants were more likely to flag somewhat related and totally unrelated words as belonging to the original list. For example, when high, people might have mistakenly said  the word "tomato" was in their original word list even if it was a sleep-themed list. 

True crime 

The results suggest that people may be particularly prone to forming spontaneous false memories while high on cannabis, especially if the misremembered details only somewhat relate to their original experience, the authors concluded. But the DRM task isn't very realistic — after all, how often are witnesses asked to memorize random words at the scene of a crime? 

To better capture a true crime scenario and examine false memories that arise from external sources, the research team used virtual reality (VR). In one simulation, the participants witnessed a fight unfolding on a train station platform, and in a second, the volunteers (while in VR) stole a handbag from someone at a bar. Half of the participants took cannabis before donning their VR gear, while the other half remained sober. 

Related: 7 ways marijuana may affect the brain

Both groups completed an interview immediately after each simulation, during which their interviewer asked leading questions laced with misinformation. For instance, a question might have wrongly implied that the attacker on the train platform wore a black coat or that he was armed with a knife. The participants also listened to a virtual co-witness give a somewhat skewed account of the event, as might happen in real life. 

When asked about true details of the virtual crimes, the sober and high groups answered the questions with similar accuracy. But when asked about details that never appeared in the simulation, the intoxicated group confirmed the inaccurate information more often than the sober group did. 

"People under the influence of cannabis show the highest risk for false memories for things or details that are poorly related to the original event," Kloft said. "It appears that [cannabis-intoxicated people] have a 'yes' bias when they are uncertain about their memory, which makes them sort of random and unreliable responders." 

Time to sober up 

The results underscore the idea that "if you question [cannabis-intoxicated] people immediately, you are going to get these false memory effects," said Manoj Doss, a postdoctoral research fellow at the Johns Hopkins Center for Psychedelics and Consciousness Research who was not involved in the study. Doss conducted a similar study using still images and written descriptions, rather than VR, and found that people who were high were more likely to falsely "remember" images they'd never seen when prompted by unfamiliar descriptions. 

But would the false memories persist after the "witnesses" sobered up? To find out, the team repeated the memory tests the following week. On the DRM task, people performed fairly similarly regardless of their state of mind during the initial experiment. If they completed the initial test while high, however, they still tended to falsely recognize unrelated words more often than their sober selves. On the VR tasks, both the sober and intoxicated groups performed similarly on the follow-up test. Presumably, these results could reflect how memory decays over time, even in sober people, Kloft said. 

"Memory decays, initially, very quickly. It declines steeply in the first 24 hours," said Annelies Vredeveldt, an associate professor in the Department of Criminal Law and Criminology at Vrije Universiteit Amsterdam and co-founder of the Amsterdam Laboratory for Legal Psychology. For this reason, it's considered best practice to interview eyewitnesses as soon as possible after a crime occurs. But in light of these new findings, the recommendation may not apply to people who are high on cannabis. 

"Probably it would be best if [cannabis-intoxicated people] were interviewed as soon as they sober up, or maybe one day after the event," Vredeveldt said. The more time that passes, however, the more their memory will deteriorate, she added. 

Although many studies have investigated the effect of alcohol on false memories, relatively few have examined how memories falter under the influence of cannabis or other popular drugs, leaving the authorities to handle intoxicated witnesses, victims and suspects without evidence-based procedures, Kloft said. "In my opinion, more research ... on other drugs and drug combinations (e.g., alcohol and cannabis) are urgently needed," she said. 

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Originally published on Live Science.