Unlocking the Mysteries of Sleep
Studies of procedural learning, however, "show clear evidence that you don't get improvement until you sleep," Siegel says.
A perfect example: studies show that when learning muscle-related tasks -- like dancing, piano playing, gymnastics -- there is significant improvement after a night's sleep, he tells WebMD.
This type of learning occurs in the cortex of the brain, Siegel explains. "The hippocampus hands out the 'episodic details' like phone numbers, what you had for breakfast this morning." The facts you crammed for today's test are likely delivered via the hippocampus.
But it's the neocortex that's working when you need to re-process information, as in learning muscle-related tasks. It's also the neocortex that will provide the answer when someone asks what you would like for breakfast, he says.
"Your neocortex would process all the information -- the fact that you prefer waffles, but the last couple of times you had them they were kinda soggy," Stickgold tells WebMD.
It's also your neocortex that makes "sleeping on a problem" -- a concept that seems known across all cultures -- so effective, he says. "You're offered the perfect job, but it's not in an ideal city. You can't decide which college is right for you. Everybody knows that you can count on the fact that if you go to bed confused, when you wake up, you'll have the answer, or the answer isn't to be found."
"I think the mysteries of sleep, of REM sleep, are yielding," says David Dinges, PhD, a sleep researcher, professor of psychology and psychiatry at the University of Pennsylvania School of Medicine.
Dinges is currently president of the Sleep Research Society, and agreed to comment on the studies for WebMD.
"As the technology gets better, our ability to penetrate the brain gets better, allowing these and other scientists to push the envelope in our understanding," Dinges tells WebMD. These are small pieces of evidence in a giant, endless puzzle."
Sleep is known to be important to cognitive function, he says. "We know that if you are sleep-deprived, it's tougher to remember, harder to think quickly, more difficult to think of new solutions. The debate among scientists is whether those are completely different functions, or are they related? Does REM sleep restabilize us from a cognitive and emotional perspective or is it necessary so that our brains can lay down memories?"
Likely so, says Dinges. "I'd be surprised if there was not some fundamental role of sleep in facilitating learning and memory, but how specific we can be remains to be debated. It's partly tied up with how we define memory and learning -- which may not be exactly how nature separates it out."