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6-minute catnap sharpens memory

/ Source: contributor

Beverly Fike calls them “power naps.”

Any time she feels her brain going dull, Fike scouts out a quiet spot and allows herself to doze – but only for 10 minutes. Experience has taught her that any longer and she’ll feel groggy. “With that quick nap, my brain works faster,” Fike says.

As it turns out, the 77-year-old from Galt, Calif., years ago figured out something that researchers have just proven to be true: the power catnap can sharpen wits.

In a new study, German researchers have shown that if you nap just six sublime minutes during the day, it will not only make you feel better but will also improve your ability to learn and remember.

The connection between sleep and learning is something that researchers have only recently pinpointed, but many people know from their own experience — such as the mathematician who says he’s going to sleep on a problem and has a Eureka! moment upon nodding off.

But what wasn’t known was just how much shut-eye was needed to get an edge. To get a better sense of that, researchers from the University of Duesseldorf performed two experiments described in the March issue of the Journal of Sleep Research.

In both experiments, students were asked to review and memorize a list of 30 words. Afterwards, study participants were either allowed to play a videogame or to take a nap in a quiet room.

In the first, researcher compared 26 university students’ abilities to remember what they’d learned after a 50-minute nap or playing a video game. In the second, the allotted naps were shortened to 35 minutes or six minutes for another 18 students.

When researchers compared the groups, they found that nap takers consistently remembered more words. On average, six-minute nappers remembered one word more than the video game players, while people taking the longer naps remembered two words more.

Benefits kick in quickly

The research suggests that most of the memory improvement is linked to changes that occur in the brain just as you start to doze off, said Olaf Lahl, a researcher at the Institute of Experimental Psychology at the University of Duesseldorf and the study’s lead author. “These processes remain active for a certain time period even if sleep is terminated shortly thereafter,” he said.

Sleep experts were surprised that just six minutes of snoozing could lead to better learning and memory. “You can’t argue with data,” said Dr. Mark Mahowald, director of the Minnesota Regional Sleep Disorders Center in Minneapolis and a professor of neurology at the University of Minnesota Medical School. “Still, this is a small group of individuals and it needs to be replicated.”

The results may help scientists get a better handle on just what happens when we go to sleep, said Matthew Tucker, a researcher at Harvard University School of Medicine and the Center for Sleep and Cognition at the Beth Israel Deaconess Medical Center in Boston.

“It’s very neat that just six minutes has this effect,” Tucker said. “And it says something about the function of sleep.”

Scientists do know that there are big changes in the brain just as a person falls asleep, Tucker said.

“There are dramatic shifts in brain chemistry and electrophysiology,” he said. “For example, we know that levels of the neurotransmitter acetylcholine go down. And we think that when acetylcholine gets to a low point, it should have an enhancing effect on memory.”

Researchers believe that the brain uses sleep as a time to consolidate memories and to choose which details to park in a permanent file and which to toss into the mental wastebasket.

This is necessary because the brain has limited storage space, Mahowald says. Just like the hard drive on a computer, the parts of the brain set aside for long-term memory storage can only accommodate so much data.

Brain's graveyard shift

You can think of sleep as the time when the brain’s graveyard shift comes on line. While the night clerk is filing away memories, the warehouse workers are restocking brain chemicals and the cleaning crew is tidying up the detritus left over from a hard day of thinking.

During sleep, the brain “gets rid of what you don’t need so that during the next period of wakefulness, you’re ready to acquire more information,” Mahowald explained.

The new study’s results might prompt more people to take power naps or to think that they might be able to replace the standard eight hours with shorter sporadic periods of slumber.

But those quickie catnaps can’t take the place of a solid night of sleep.

“I suspect that sleep has some unknown primary function other than memory consolidation,” Lahl said. “A regular sleep schedule still plays an important role in overall well-being and health.”

Linda Carroll is a health and science writer living in New Jersey. Her work has appeared in The New York Times, Newsday, Health magazine and SmartMoney.