Donald Trump is known for his lack of sleep (tweeting in the small hours of the morning). Problem is he's got a growing nation of insomniacs, frightened awake at his erratic, upsetting behavior. What is sleep and why do we need it to maintain health? This article from the Dana Foundation gives an overview. Learn about brain essentials in our book, Healing the Brain.
A good deal of progress has been made recently in understanding
why sleep is so important. Recent studies have shown that both acute sleep
deprivation (staying awake all night) and chronic sleep restriction (sleeping
only a few hours/night for 1-2 weeks) impair many cognitive functions, from
vigilance and attention to speech and humor appreciation.
We also know that it
may take more than one or two days to recover after chronic sleep loss, so
oversleeping during the week-end may not be enough, if the accumulated sleep
debt is large. There is also strong evidence that sleep need varies
significantly among individuals, although why some of us can function well with
much less sleep than others remains unclear. Other studies show that a night of
sleep benefits the acquisition of new information the next day (new learning
during sleep, instead, remains largely a dream).
Sleep also leads to
the consolidation and integration of memories, both declarative memories - those
one can recollect consciously, such as lists of words or associations between
pictures and places, as well as non-declarative memories such as perceptual and
motor skills. These experimental results fit the common observation that after
intensive learning, say practicing a piece over and over on the guitar,
performance often becomes fluid only after a night of sleep. It is likely that
when we learn and repeatedly activate certain brain circuits, many synapses end
up strengthening, not only when you play the right notes well, but also when you
do it badly, or fumble other notes. The result is that, while by practicing you
get better and better on average, your performance remains a bit noisy and
After sleep, it is as if the core of what you learned had been
preserved, whereas the chaff is eliminated - that is, sleep seems to notch-up
the signal-to-noise ratio. Something similar may happen also with declarative
memories: in the face of the hundreds of thousands of scenes we encounter in
waking life, memory is particularly effective at gist extraction, where
the details (the noise) may be lost, but the main point of what happened to us
(the signal) is preserved. So far, it seems that the memory benefits of sleep,
especially for declarative memories, are due primarily to NREM sleep, but in
some instances REM sleep or a combination of NREM-REM cycles may also play a
role. One should not forget that memories can also consolidate during wake.
Moreover, to some extent sleep helps memory consolidation simply because it
reduces the interference caused by later memory traces.
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