GUY RAZ, host:
Two floors above my head here in the studio at NPR, on the fourth floor, there's a quiet room that's informally known as the nap room. It's a place where worn-out journalists catch up on a few minutes of sleep when they need it.
Well, according to a recent study, those short naps may help your brain work better.
Matthew Walker led that study. He researches sleep at the University of California, Berkeley.
Matthew Walker, welcome to the program.
Professor MATTHEW WALKER (Sleep and Neuroimaging Laboratory, Department of Psychology, University of California Berkeley): Thank you, nice to be here.
RAZ: Now, it's not exactly breaking news that getting, you know, sleep now and then get - helps you function. So what's the question you were trying to answer with this study?
Prof. WALKER: Well, despite us all knowing the sort of subjective benefits of sleep, what may be surprising to the general public is that scientists and doctors do not still have a satisfying answer as to why we sleep, and that's, of course, one-third of our lives.
And what has been probably known for some time is that sleep after learning is critical to sort of cement those new memories into the neural architecture of the brain.
But what we've understood less is whether sleep before learning is equally important in sort of preparing your brain almost like a dry sponge, ready to soak up new information the next day, and that was really what we were focusing on here.
RAZ: So tell me how you tested this question.
Prof. WALKER: So we took two groups of healthy, young adults, and both of them performed two separate learning sessions. But the thing that differentiated the two groups was that after the first learning session but before the second learning session, one-half of those participants actually had a 90-minute sleep opportunity, a 90-minute nap in the middle of the afternoon, whilst the other group remained awake.
RAZ: So what did you find?
Prof. WALKER: So what we found was that across the day, those people who remained awake got about 10 percent worse in their ability to learn, whilst those who had a nap improved by about 10 percent. So at the end of the day, there's a difference of about 20 percent between those two.
RAZ: What does it tell us about what's happening in our brains when we sleep?
Prof. WALKER: What we believe happens is that when we initially learn information, that information is bound and sort of collected together by one specific part of the brain, a region that we call the hippocampus. But what we also believe is that that area is almost the - sort of the short-term reservoir for that newly learned memory. And for that memory to persist and survive, it has to pass into a more long-term storage location in the brain, and that's in an area that we call the cortex, which is this folded mass of tissue on the top of your brain.
And what we've hypothesized is that perhaps during sleep and particular stages of sleep, that information is actually shifted from one location, the hippocampus, to another, the cortex. So there's a dual benefit, perhaps a shifting of memory, a change in the geography of information at night that allows you to efficiently learn the next day.
RAZ: What do you think the practical applications of this ought to be? I mean, should high schools or, you know, offices schedule nap time during the day?
Prof. WALKER: Yeah, it's an interesting question. At some point, we as adults just stop ourselves sort of thinking that there's a benefit of sleep. And instead, which is even worse, we start to associate sufficient sleep with laziness.
Now, think about that in the context of children. You would never look at a child who is sleeping sufficient amounts and think: Well, what a lazy infant. And so it's a funny paradox that we find ourselves in as adults, where we seem to think sleep is perhaps more of a luxury that we can choose or choose not to engage in, instead of realizing that in fact, as we're understanding more through science, that it's a biological necessity.
RAZ: Matthew Walker is a psychology professor and a sleep researcher at the University of California, Berkeley. And Matthew Walker, I'm going to go take a nap right now.
Mr. WALKER: Sound good. Sleep well.
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