BEIJING, Oct. 23 (Xinhuanet) -- Dramatic overreaction
in the emotional centers of our brain to bad experiences is one result of a lack
of sleep, research detailed in the Oct. 23 issue of the journal Current Biology
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," researcher Matthew Walker, a
neuroscientist at the University of California, Berkeley, told LiveScience.
Although 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 ¡ª 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 ¡ª 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."
Future research can focus on which components of
sleep help restore emotional stability ¡ª "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," Walker added.
(Agencies)
