WASHINGTON — Just in time for the holidays, some medical advice most people will like: Take a nap.
Interrupting sleep seriously disrupts memory-making, compelling new research suggests. But on the flip side, taking a nap may boost a sophisticated kind of memory that helps us see the big picture and get creative.
“Not only do we need to remember to sleep, but most certainly we sleep to remember,” is how Dr. William Fishbein, a cognitive neuroscientist at the City University of New York, put it at a meeting of the Society for Neuroscience last week.
Way too little sleep clearly is dangerous: Sleep deprivation causes not just car crashes but all sorts of other accidents. Over time, a chronic lack of sleep can erode the body in ways that leave us more vulnerable to heart disease, diabetes and other illnesses.
But perhaps more common than insomnia is fragmented sleep — the easy awakening that comes with aging or sleep apnea.
Scientists increasingly are focusing less on sleep duration and more on the quality of sleep, what’s called sleep intensity, in studying how sleep helps the brain process memories so they stick. Particularly important is “slow-wave sleep,” a period of very deep sleep that comes earlier than better-known REM sleep, or dreaming time.
Fishbein suspected brains keep working during naps to solve problems and come up with new ideas. So he and graduate student Hiuyan Lau devised a simple test: documenting relational memory, where the brain puts together separately learned facts in new ways.
They taught 20 English-Âspeaking college students lists of Chinese words spelled with two characters. Then half the students took a 90-minute nap.
Upon awakening, they took a multiple-choice test of Chinese words they’d never seen before. The nappers did much better at automatically learning that the first of the two-pair characters in the words they’d memorized earlier always meant the same thing — female, for example. So they also were more likely than non-nappers to choose that a new word containing that character meant “princess” and not “ape.”
Conversely, Wisconsin researchers briefly interrupted nighttime slow-wave sleep by playing a beep — just loudly enough to disturb sleep but not awaken — and found those people couldn’t remember a task they’d learned the day before as well as people whose slow-wave sleep wasn’t disrupted.
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