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Matthew Walker, of the University of California Berkeley, and colleagues at Harvard University have published a study on sleep deprivation in the journal Current Biology.
Using functional magnetic resonance imaging (fMRI), they kept half their young adult volunteers awake for an entire day, night, and then another full day. The other half slept normally.
Two full days without sleep, the brain images showed, seemed to rewire their brains, redirecting activity from the calming and rational prefrontal cortex to the “fear center” — the amygdala.
“It’s almost as though without sleep the brain had reverted back to more primitive patterns of activity, in that it was unable to put emotional experiences into context and produce controlled, appropriate responses,” said Walker.
It’s not news that a lack of sleep can make people grumpy. “We all know implicitly the link between bad sleep the night before and bad mood the next day. We are just adding the brain basis to what we know.”
According to Walker, “We found a strong overreaction from the emotional centers of the brain. It was almost as if the brain had been rewired, and connected to the fright, flight or fight area in the brain stem.”
Lab workers noticed a difference in behavior of the sleep-deprived volunteers.
“They seemed to swing like a pendulum between the broad spectrum of emotions,” Walker said. “They would go from being remarkably upset at one time to where they found the same thing funny. They were almost giddy — punch drunk.”
Next, Walker would like to test people who are chronicallly sleep deprived, perhaps by letting them have just five hours of sleep over several days. (The average adult need 7 to 9 hours of sleep a night.)
He said the findings may shed light on psychiatric diseases. “This is the first set of experiments that demonstrate that even healthy people’s brains mimic certain pathological psychiatric patterns when deprived of sleep.”
“Before, it was difficult to separate out the effect of sleep versus the disease itself. Now we’re closer to being able to look into whether the person has a psychiatric disease or a sleep disorder.”
In the same issue of the journal, a second study suggests that daylight-savings time regimes may cause similar effects.
Till Roenneberg of Ludwig-Maximillian University in Munich, Germany examined the sleep patterns of people in Central Europe.
He found people’s internal circadian clocks adjusted when the clock moved back in the autumn months, but failed to adjust when it moved forward, costing them an hour of sleep, in the spring.
The effects held for weeks, he said, perhaps causing people to feel continually sleep-deprived in the spring and summer.
sole source: online from Reuters, article by Maggie Fox on October 24, 2007. www.reuters.com
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