What’s the News: By videotaping sleepwalkers as they got some shut-eye (with their permission, of course), French and Swiss researchers caught on tape what other studies have deduced through brain recordings and memory tasks: As we sleep, our brains seem to replay what we learned during the day. See an example of a a sleepwalker's re-enactments here: How the Heck:
The researchers recruited 19 sleepwalkers and 20 people with sleep behavior disorder, who physically act out their dreams, plus 18 people without any sleep disorders.
All the subjects learned a physical skill: hitting particular buttons arrayed around them in response to different prompts from a computer.
The researchers then videotaped each person as they slept. One of the sleepwalkers lifted her arms during REM sleep and started moving her hands in a familiar pattern: an “obvious and accurate re-enactment of a short fragment of the recently learned sequence of movements,” the researchers wrote.
What’s the Context:
Most of these studies have compared how sleep-deprived and well-rested people performed on memory tests, or looked at how closely brain activity during sleep resembled brain activity as people learned something new. Watching people who act out their thoughts as they sleep provides a more direct view of what the brain’s up to.
Not So Fast:
Some scientists think that sleep’s impact on memory isn’t as simple as locking down everything we’ve learned. Sleep may only solidify memories when we know we’ll be tested, or may actually help us prune unimportant memories rather than fortify the important ones.