As to why sleep has the effects of long term memory and how that information can be used to your advantage are questions still under study, said Dr. Robert Stickgold, an associate professor of psychiatry at Harvard Medical School and director of the Center for Sleep and Cognition at Beth Israel Deaconess Medical Center in Boston.
The sleeping brain is not stupid, said Jessica Payne, an assistant professor of psychology at the University of Notre Dame in Indiana, who has researched the effect of sleep on memory. It's smart, and it's making sophisticated decisions about which memories are important and should be held onto.
He said, sleep helps in the whole information-processing part of the picture. It might be that sleep is an amount of time to give the brain a chance to go offline and shift into a different psychological mode that's evolved to perform certain types of memory processing, Stickgold said.
Though there's still much to be learned, he said, research suggests that REM sleep -- the stage of sleep involving rapid eye movement -- seems to be the phase that resolves the issue, or tells you what to do with new information.
In her research, Payne said, she's found that a good night's sleep can lead to better inferential ability. In other words: You may learn about a concrete relationship between A and B and B and C, but you don't see there might be an A and C connection, she said. Our evidence suggests that when you sleep, you learn the hierarchy of information, you learn to extract the more sophisticated relationships.
Sleep is not only important for your ability to remember, she said, but it also helps you be more creative, find more interesting and distant connections and be more innovative.
In truth, he said, sleep deprivation has been linked with obesity because it disrupts insulin regulation, in turn easing weight gain. And the sleep-and-illness and sleep-and-memory links are well known.
Though the amount of sleep needed does vary, Stickgold has an easy test to decide if you're getting enough. Watch what happens on the weekend if you don't set an alarm, he said. If you sleep more than you sleep during the week, you aren't getting enough sleep.
Stickgold suspects that anyone who does this will find that lots of daily tasks -- driving and checkbook balancing among them -- will become easier. And along with that might come the realization that getting an extra hour or two of sleep a night can pay big -- and perhaps even life-saving -- benefits.