A great many processes occur in our brains, and only while we’re asleep. Researchers have just discovered a new one, describing how the brain produces special chemicals while we’re asleep to not only form memories, but also to relive past events our subconscious is interested in remembering.
Reporting at the 2014 Society for Neuroscience meeting earlier this month in the US, sleep researcher from the University of Pennsylvania, Jennifer Choi Tudor, presented to her peers a new study involving the sleep-induced brain chemical, 4EBP2.
According to Jon Hamilton at NPR, previous research has shown that when you deprive lab mice of sleep, they will struggle to remember things, and their brains will contain lower levels of 4EBP2. To figure out if there was a connection between these two factors, Choi Tudor and her team injected extra 4EBP2 into the mouse brains, and then kept them up all night. "With the injection, their memory is normal," Tudor told Hamilton.
The next part of the experiment was investigating how new memories are formed, and existing ones changed during the process of sleep. The team monitored the brains of the mice while they are awake and going about their business in their cages. They watched as specific brain cells activated exclusively when the mice had entered specific regions of their cage.
In one area, certain brain cells activated, in the next, another set of brain cells lit up, and in the next area, and the next, and so on. That night, brain scans revealed that the same sequence of brain cells being activated occurred, suggesting that the mice were subconsciously retracing their steps in their sleep, likely to help them remember where they’ve been.
Knowing this, is it possible to change this formation of memories? One of the team, Karim Benchenane from the National Centre for Scientific Research in Paris, France was in charge of finding out. According to Hamilton at NPR, Benchenane’s team stimulated the pleasure centre in the mouse brains while they were awake, every time they entered a specific region of their cage.
The hope was that if they repeated this process enough times, that specific place would be subconsciously connected to a pleasant memory. "And sure enough, when the animals woke up, they went straight to that location, looking for a pleasurable reward,” says Hamilton.
The research might sound a little creepy - in that the researchers are artificially manipulating the minds of their mice to create positive memories - but it’s offering real hope to people who have to deal with the sometimes crippling experience of post-traumatic stress disorder. It’s not about zapping a person’s brain and making them forget, it’s about the possibility of identifying when a person is dreaming about a traumatic experience, ‘deleting’ the negative association and replacing it with a nice one. Essentially, giving the brain a chance to correct the lingering and unhealthy bad feelings associated with a past event.
Strangely enough, says Hamilton at NPR, a separate team reported that late-night snacks could be messing with the brain’s ability to form memories when we sleep. The researchers, from the University of California, Los Angeles, found that when they fed their mice during their normal bed times, they ended up under-performing in memory tests the next day, even if they got their normal amount of sleep. Something to remember if you’ve got an exam coming up...