By scanning your brain, scientists can tell what memory you are recalling.
Scientists have made impressive gains recently when it comes to reading minds. For instance, through brain scans, researchers can tell what number a person has just seen, figure out what letters a person wants to type, and determine where people were standing within virtual reality environments.
To see if they could discern even more complex information during mind-reading, scientists more recently had 10 volunteers watch three films, each seven-seconds long and featuring a different actress in a fairly similar everyday scenario on a typical urban street. For instance, in one movie, a woman rifled through her purse to find an envelope she then dropped into a mailbox, while in another, an actress finished her cup of coffee, which she then dropped into a trashcan. Participants watched the films 15 times.
The researchers scanned the participants' brains using functional magnetic resonance imaging (fMRI) while the participants were asked to recall the films. The data was run through a computer algorithm to identify brain activity patterns linked with memories for each of the movies. Using these patterns, the researchers could accurately predict which film volunteers were recalling as they had their brains scanned.
"The algorithm was able to predict correctly which of the three films the volunteer was recalling significantly above what would be expected by chance," explained researcher Martin Chadwick at University College London. "This suggests that our memories are recorded in a regular pattern."
These kinds of memories are episodic memories — "the complex, everyday memories that include much more information on where we are, what we are doing and how we feel," said researcher Eleanor Maguire, a cognitive neuroscientist at University College London.
The signatures of each specific episodic memory they looked at were definitely found in the brain area known as the hippocampus, which is critical for learning and memory, as well as this area's immediate neighbors. In particular, three areas of the hippocampus — the rear right and the front left and front right areas — seemed to be involved consistently in all the volunteers. Past research hinted the rear right area is where spatial information is recorded, but it remains unclear what role the front two regions play.
In these experiments, the researchers exposed volunteers to movies roughly an hour before scanning took place.
"It would be extremely interesting to consider what would happen if we brought them back the next day or in a week's time or in a month's time or even a year's time," Maguire noted. "Does the memory trace degrade, does it change over time, do other brain areas assume responsibility for the memories? It also leads into future research looking at the effect of perhaps age in general on memories and perhaps how memories are affected by brain injury and disease."
The scientists detailed their findings online March 11 in the journal Current Biology.