Do you remember your dreams?
People who recall certain types of dreams—those in which they’re rehearsing a skill like riding a unicycle or skiing downhill—have a leg up on people who do not recall such dreams. They’re generally able to master skills faster.
This is one of many fascinating bits of information I learned listening to Terry Gross’s interview of neuroscientist Penelope Lewis, whose new book, The Secret World of Sleep: The Surprising Science of the Mind at Rest, is set for release this month. (Click here to listen to the full interview on NPR’s Fresh Air.)
Lewis, who directs the Sleep and Memory Lab at the University of Manchester in England, is mainly interested in how sleep affects memory. “Memories evolve constantly,” she said, “and a lot of that evolution occurs when we’re asleep.”
Excerpts from the Interview
1) Sleep helps to strengthen memories. “Supposing you are learning to play the piano,” Lewis said. “You’re moving your fingers a lot. That’s associated with responses in motor areas of your brain. . . . Those areas will become active again while you’re asleep, and that replay—or reactivation—is what we think is responsible for the strengthening. So it’s kind of like your brain is rehearsing stuff without you knowing, while you’re asleep.”
2) But sleep doesn’t only strengthen memories. Sleep helps us synthesize information and understand what’s important and what’s not. “It’s about extracting out the gist or maybe the main points” of what you’ve learned, she said.
3) At the same time as sleep serves to strengthen memories, it also enables us to forget. “Across the day while we’re busy doing things, experiencing things, seeing things, hearing things, learning things, processing different kinds of information, the connections between neurons in the brain get strengthened because they’re trying to retain all of this information,” Lewis said. “And an awful lot of it is garbage; it’s stuff you don’t want to remember or don’t care about—what you had for breakfast, or the color of a stain on the cover of a book or something. It’s really not useful or interesting.”
“And the problem is, if you keep storing all of this stuff, you reach capacity and you can’t keep storing more. And so what happens during sleep, and specifically during the deep stage of sleep that we call slow-wave sleep, is that all of those synapses get downscaled again. So where they’ve been strengthened up, they all get proportionally downscaled.”
These are just a few points Lewis touches on her interview, which, for those of us interested in what goes on in our heads at night, is well worth a listen. I’m guessing her book will make for a good read.