LSD alters consciousness by breaking down barriers in the brain

A colorful illustration of the concept of a brain on psychedelics. — (Image credit: Shutterstock)

LSD may alter consciousness by freeing the brain from its natural barriers, allowing neurons that wouldn't normally interact, to have unusual conversations, brain scans show.

Investigating how "mind-altering" substances such as LSD can change the brain can be a "powerful method for interrogating and understanding" how the mind meets the brain, the authors wrote in the study, first reported by PsyPost.

The brain is made up of 86 billion neurons that communicate with each other over a network of connections. With limited space in the skull, not every neuron has a direct connection to every other neuron, and each person's brain is wired a bit differently. But neuroscientists have created maps that roughly sketch out which brain regions tend to be more or less connected to each other, in the average person.

"If you think of brain structure as roads, brain function is the traffic," said lead author Andrea Luppi, a doctoral candidate in the cognition and
consciousness imaging group at the University of Cambridge in the U.K. In other words, this underlying infrastructure creates limits on which brain regions can exchange information. "LSD did not change the layout of the roads, but it did change the traffic," Luppi told Live Science in an email.

To figure this out, Luppi's colleagues at Imperial College London recruited 20 healthy volunteers who had all previously used psychedelic drugs. Each volunteer underwent two functional magnetic resonance imaging (fMRI) scans, two weeks apart. Before one of the scans, they were given salty water as a placebo, and before the other they were given 75 micrograms of LSD dissolved in salty water. The participants closed their eyes and rested as their brains were scanned. They later completed a subjective evaluation of their experience.

Under the influence of LSD, "the brain is free to explore a variety of functional connectivity patterns that go beyond those dictated by anatomy — presumably resulting in the unusual beliefs and experiences reported during the psychedelic state," the authors wrote. Understanding how exactly psychedelics affect brain function "may hold further promise for our understanding of the therapeutic effects," the authors wrote.

Yasemin is a staff writer at Live Science, covering health, neuroscience and biology. Her work has appeared in Scientific American, Science and the San Jose Mercury News. She has a bachelor's degree in biomedical engineering from the University of Connecticut and a graduate certificate in science communication from the University of California, Santa Cruz.