Unlocking the Mysteries of Sleep
Nov. 1, 2001 -- "I'll sleep on it" may seem like a last resort when problems get too murky. But new science is revealing why this time-tested remedy works. Researchers are also learning more about the role that sleep plays -- or doesn't play -- in helping us cram for tests or learn new skills like dancing, tennis, and the piano.
The studies appear in the current issue of the journal Science.
Researchers have long debated the connection between REM (rapid eye movement) sleep and learning. A popular notion has been that sleeping allows the brain to consolidate memories, to facilitate learning. But one group of researchers finds just the opposite, that sleep plays little role in helping us learn new material.
"Learning occurs during alert, waking hours, not during sleep," says Jerome M. Siegel, PhD, professor of psychiatry at UCLA and chief of neurobiology research at Sepulveda VA Medical Center in Los Angeles.
If anything, getting a good night's sleep helps with concentration -- that's the benefit, Siegel tells WebMD. "It's very important to be well-rested if you want to learn something. You don't want to fall asleep in the test. It's like eating before a test; you have to take care of yourself. It's not that REM sleep helps learning. It's not important for memory."
In his paper, Siegel reviewed numerous animal and human studies, looking at the effects of REM sleep. Many found that depriving animals and humans of REM sleep did not impair their ability to form long-term memories.
"The switch from temporary memory to permanent memory seems to occur during waking hours," he says. "You don't need sleep to retain it."
There are plenty of people who have no REM sleep -- for various reasons -- who don't have memory problems, Siegel says. People taking drugs known as MAO inhibitors for depression are a perfect example; so are some brain injury patients.
Also, people who learn very well -- those with high IQs -- do not seem to have any pattern of greater REM sleep than those who are retarded. Likewise, some of the smartest animals -- dolphins, whales -- get very little REM sleep whereas the platypus, an entirely instinct-driven animal, gets more REM sleep than any other animal.
In fact, among all the animals, humans don't have especially high or low amounts of REM sleep, he tells WebMD. "We really don't know the purpose of REM sleep," Siegel says. "We don't even fully understand learning."
REM sleep may actually help us with certain types of learning -- what's called "procedural" learning, "when you're learning how rather than what," says Robert Stickgold, PhD, assistant professor of psychiatry at Harvard Medical School and a cognitive neuroscientist.
Stickgold agrees with Siegel, that "simple declarative memory" -- like remembering facts for a test, phone numbers, or word lists -- is not dependent on sleep. "Everything we learn while waking gets learned before we sleep. So clearly those are not dependent on sleep for their initial consolidation," he tells WebMD.