Why sleeping on a problem often helps

Kate Ravilious, "Why sleeping on a problem often helps", Guardian,
October 27, 2005,
Link:
http://education.guardian.co.uk/high...601430,00.html

For sleep researchers it has been a mystery tinged with irony: why is
it that when we are faced with a tricky problem, the solution is much
clearer if we sleep on it?

The answer, according to a series of papers in the journal Nature
today, lies in the hidden goings on in our brains while we slumber. In
different stages of sleep our brains piece together thoughts and
experiences, then file them in a structured way, giving us clearer
memories and ultimately, better judgment.

Most people spend around a third of their lives asleep, and each
nightly cycle can be divided into five stages that each take on a
separate role in helping us organise our thoughts and consolidate our
memories. "It seems that different kinds of memories are enhanced by
different kinds of sleep and this may be why we have the different
stages of sleep," said Robert Stickgold, a sleep researcher at Harvard
medical school in Boston.

Recent experiments suggest the final stage of sleep, rapid eye movement
(REM) sleep, is crucial for reorganising and cross-referencing our
memories, while non-REM "slow-wave-sleep" plays more of a role in
re-enforcing our memories. "If people are deprived of their REM sleep
then their learning doesn't improve," Professor Stickgold said.

Brain imaging has shown that the brain works in a different way after a
good night's sleep. In an experiment where people were asked to learn
to tap simple numerical sequences on a computer keyboard they improved
significantly after a night of sleep. The brain images showed that
different regions of the brain were activated before and after sleep.
"Sleep seems to nail down the information we have and reorganise the
way it is stored in the brain," Prof Stickgold added. Which perhaps
explains why sleeping on a problem often provides the best solution.

While scientists are sure sleep is crucial to help us store memories,
the extremes of time spent sleeping seen in the animal kingdom have
been another source of puzzlement. But studies of the varying sleep
patterns of animals are revealing extraordinary details of why we sleep
as much as we do, and why other creatures seem to go without or sleep
continuously.

Jerome Siegel of University of California, Los Angeles, in a paper in
Nature today, describes how diet and lifestyle have a huge effect on
how much sleep an animal gets. Carnivores spend most of the day dozing,
omnivores sleep a moderate amount, and herbivores nap when they can.
"These conclusions explain why some animals can survive and reproduce
optimally with only a few waking hours, whereas others need to eat all
day and must have reduced sleep time," he told Nature.