Without sleep, the emotional centers of our brains dramatically
overreact to bad experiences, research now reveals.
"When we're sleep deprived, it's really as if the brain is
reverting to more primitive behavior, regressing in terms of the
control humans normally have over their emotions," said researcher
Matthew Walker, a neuroscientist at the University of California,
Berkeley.
Anyone who has ever gone without a good night's sleep is aware
that doing so can make a person emotionally irrational. While past
studies have revealed that sleep loss can impair the immune system
and brain processes such as learning and memory, there has been
surprisingly little research into why sleep deprivation affects
emotions, Walker said.
Walker and his colleagues had 26 healthy volunteers either get
normal sleep or get sleep deprived, making them stay awake for
roughly 35 hours. On the following day, the researchers scanned
brain activity in volunteers using functional magnetic resonance
imaging (fMRI) while they viewed 100 images. These started off as
emotionally neutral, such as photos of spoons or baskets, but they
became increasingly negative in tone over time -- for instance,
pictures of attacking sharks or vipers.
"While we predicted that the emotional centers of the brain
would overreact after sleep deprivation, we didn't predict they'd
overreact as much as they did," Walker said. "They became more than
60 percent more reactive to negative emotional stimuli. That's a
whopping increase -- the emotional parts of the brain just seem to
run amok."
The researchers pinpointed this hyperactive response to a
shutdown of the prefrontal lobe, a brain region that normally keeps
emotions under control. This structure is relatively new in human
evolution, "and so it may not yet have adapted ways to cope with
certain biological extremes," Walker speculated. "Human beings are
one of the few species that really deprive themselves of sleep.
It's a real oddity in nature."
In modern life, people often deprive themselves of sleep "almost
on a daily basis," Walker said. "Alarm bells should be ringing
about that behavior -- no pun intended."
Future research can focus on which components of sleep help
restore emotional stability -- "whether it's dreaming REM sleep or
slow-wave, non-dreaming forms of sleep," Walker said.
Many psychiatric disorders, "particularly ones involving
emotions, seem to be linked with abnormal sleep," he added.
"Traditionally people mostly thought the psychiatric disorders were
contributing to the sleep abnormalities, but of course it could be
the other way around. If we can find out which parts of sleep are
most key to emotional stability, we already have a good range of
drugs that can push and pull at these kinds of sleep and maybe help
treat certain kinds of psychiatric conditions."
The findings are detailed in the Oct. 23 issue of the journal
Current Biology.
(Agencies via China Daily October 24, 2007)