美国神经学专家研究发现，午睡有助促进人的复杂记忆，使思维更开阔、更具创造性；而人们如果在“慢波睡眠”即深度睡眠阶段遭到打扰，则可能会忘记前一天获知的事情。纽约市立大学认知神经科学博士威廉•菲什拜因和一名研究人员以20名英语为母语的大学生为研究对象，探求午睡对他们通过记忆把所学事物相联系能力的影响。测试结果表明，午睡过的学生能够总结出已学词语含义上的共同特点，做出正确推断选择，得分高于未午睡学生。

Take a nap. Interrupting sleep seriously disrupts memory-making, compelling new research suggests. But on the flip¹ side, taking a nap may boost a sophisticated kind of memory that helps us see the big picture and get creative.

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 cognitive² neuroscientist at the City University of New York, put it at a meeting of the Society for Neuroscience last week.

Good sleep is a casualty of our 24/7 world. Surveys suggest few adults attain³ the recommended seven to eight hours a night.

Way too little clearly is dangerous: Sleep deprivation⁴ causes not just car crashes but all sorts of other accidents. Over time, a chronic⁵ lack of sleep can erode⁶ the body in ways that leave us more vulnerable to heart disease, diabetes⁷ and other illnesses.

But perhaps more common than insomnia⁸ is fragmented sleep — the easy awakening¹⁰ that comes with aging, or, worse, thesleep apnea that afflicts¹¹ millions, who quit breathing for 30 seconds or so over and over throughout the night.

Indeed, scientists increasingly are focusing less on sleep duration and more on the quality of sleep, what's called sleep intensity¹², 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 a more active role for the slow-wave sleep that can emerge even in a power nap. Maybe our brains keep working during that time 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.

First, they taught 20 English-speaking college students lists of Chinese words spelled with two characters — such as sister, mother, maid. Then half the students took a nap, being monitored to be sure they didn't move from slow-wave sleep into the REM stage.

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."

"The nap group has essentially¹³ teased out what's going on," Fishbein concludes.

These students took a 90-minute nap, quite a luxury for most adults. But even a 12-minute nap can boost some forms of memory, adds Dr. Robert Stickgold of Harvard Medical School.

Conversely, Wisconsin researchers briefly¹⁴ interrupted nighttime slow-wave sleep by playing a beep — just loudly enough to disturb sleep but not awaken⁹ — 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.

That brings us back to fragmented sleep, whether from aging or apnea. It can suppress the birth of new brain cells in the hippocampus, where memory-making begins — enough to hinder learning weeks after sleep returns to normal, warns Dr. Dennis McGinty of the University of California, Los Angeles.

To prove a lasting¹⁵ effect, McGinty mimicked¹⁶ human sleep apnea in rats. He hooked them to brain monitors and made them sleep on a treadmill¹⁷. Whenever the monitors detected 30 seconds of sleep, the treadmill briefly switched on. After 12 days of this sleep disturbance¹⁸, McGinty let the rats sleep peacefully for as long as they wanted for the next two weeks.

The catch-up sleep didn't help: Rested rats used room cues to quickly learn the escape hole in a maze¹⁹. Those with fragmented sleep two weeks earlier couldn't, only randomly²⁰ stumbling upon the escape.

None of the new work is enough, yet, to pinpoint²¹ the minimum sleep needed for optimal²² memory. What's needed may vary considerably²³ from person to person.

"A short sleeper²⁴ may have a very efficient deep sleep even if they sleep only four hours," notes Dr. Chiara Cirellia of the University of Wisconsin, Madison.

But altogether, the findings do suggest some practical advice: Get apnea treated. Avoid what Harvard's Stickgold calls "sleep bulimia," super-late nights followed by sleep-in weekends. And don't feel guilty for napping.