Mysterious things that happen to your body while
you sleep: John Steinbeck once noted that “it is a
common experience that a problem difficult at night
is resolved in the morning after the committee of
sleep has worked on it.” When my head hits the
pillow and I can’t seem to turn off my thoughts, I
like to picture the committee gathering in a miniature
boardroom in my brain. I imagine tiny committee
members heatedly arguing over my dilemmas while I
snooze. What a relief to leave the toughest calls up
to somebody else.
Whether you’ve imagined it or not, you’ve
probably benefited from such a committee’s
hard work. While we doze, our brains and
bodies aren’t slacking off, they’re at work,
repairing us after the day’s battles and
refueling us for tomorrow’s slog—in more
ways than you likely realize.
There’s probably no teeny boardroom. But
here’s what’s actually going on while you’re
conked out:
- You aren’t sleeping deeply
most of the time.
Not all sleep was created equal: When you
first drift off, you get only very light sleep,
then progress deeper and deeper into
dreamland. The sleep cycle starts in what’s
called non–rapid eye movement or NREM
stage 1 (the kind of sleep you might nab if
you were the type to doze off during your
college lectures; you know who you are).
Then you move into a deeper NREM 2 and
then to the deepest, NREM 3, also called
slow-wave sleep. Finally, you land in rapid
eye movement, or REM, sleep, the wild part
of the ride when most of our dreams occur.
The whole shebang usually takes
somewhere between 90 and 120 minutes, so
on a typical night you’ll cycle through four
or five times, waking up for just a sec
As the night goes on, you spend less time in
that deliciously deep stage 3 and more time
in REM sleep, which explains why your
alarm so often wakes you up in the middle
of a totally bizarre dream, says Sigrid C.
Veasey, MD, a neuroscientist and a
professor of medicine at the University of
Pennsylvania’s Center for Sleep and
Circadian Neurobiology. But we don’t really
know why REM periods get longer in the wee
hours, says Daniel A. Barone, MD, an
assistant professor of neurology at the Weill
Cornell Medical College’s Center for Sleep
Medicine. One theory, he says, is that REM
sleep may somehow prepare you to get your
butt out of bed. - Your brain cleans house.
Our brains are “on” throughout the night,
especially in that dream-heavy REM sleep,
Barone says, when they’re actually almost
as active as they are when we’re wide
awake.
Among other things, they may be taking out
the trash. That’s one of the more exciting
new ideas about the purpose of sleep: A
2013 study in mice found that waste
removal systems in the brain are more
active during sleep. Perhaps, the
researchers theorized, we sleep to allow
time to clear away toxic byproducts that
would otherwise pile up and cause
problems, like the trademark plaques of
Alzheimer’s disease, Veasey says.
Your brain’s also busy cementing new
memories while you sleep. “We think the
brain is processing the information we
gained throughout the day and filtering out
the information we don’t need, which may
be one of the reasons we dream,” Barone
says. The theory goes that maybe
connections between brain cells are
strengthened or weakened during sleep,
depending on how much we used them
during the day, he says. The important stuff
gets reinforced while the factoids we just
don’t need get trashed.