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Wednesday
Mar302011

Can Too Little Sleep Leave You Laughing?

Erik Snyder/Photodisc(NEW YORK) -- It's easy to spot someone who has missed an entire night of sleep. Grumpy. Irritable. Focusing on the negative. Now scientists at the University of California, Berkeley, and the Harvard Medical School suggest adding a new word to that list -- euphoric.

Researchers have found evidence that the human brain, deprived of sleep, swings both ways, focusing on positive, as well as negative, experiences. And, they add, that's not necessarily a good thing.

According to their study, published in the current issue of the Journal of Neuroscience, sleep deprivation sensitizes the networks in the brain that have long been associated with rewards. And that, they suggest, could contribute to rash decisions and risky behavior.

"Our previous research showed that when you are sleep deprived your brain is excessively reactive to negative or unpleasant emotional experiences," psychologist Matthew Walker of UC Berkeley said. "But what we didn't know at the end of that study is what happens on the other side of the coin. What happens when you are sleep deprived and you see rewarding stimuli or experiences?”

Some who suffer from severe depression appear to get better if they are deprived of sleep, but the benefit is often short lived. Walker wondered if healthy adults would also look on the bright side of life if they missed an entire night of sleep. He noted that people who have partied or worked through the night are sometimes giddy and prone to giggling. Is it real, or are they just punch drunk?

To find out, he and his colleagues recruited 27 adults, age 18-30, and divided them into two groups. Some of the participants lived a normal couple of days, separated by a full night of sleep. The rest were confined to the sleep lab at Berkeley, where they ate a normal diet, but were kept awake for an entire night. They got no caffeine, no alcohol and not even a brief nap.

The experimenters monitored the participants throughout the period, ensuring that none of them fell asleep even for a few minutes. During the experiment each of the participants, both the sleepers and the none sleepers, were shown a series of 100 images and instructed to push a button indicating if each image was neutral or pleasant. And they did this while inside a brain scanner.The images were roughly half and half, with around 50 percent positive and the rest neutral. And that's exactly what the sleepers found. But the non-sleepers found far more of the images pleasurable than the sleepers, suggesting they wanted to look for positive experiences. And the brain scans revealed something that the experimenters found very interesting. Participants who had missed a night of sleep were dramatically affected by the images.

"The regions of the brain showed extensive reactivity to the emotionally positive pictures, and it was appearing in the classical reward centers of the brain largely regulated by the chemical dopamine, which is obviously associated with pleasure," Walker said. "It's as though the sleep-deprived brain swings equally in both emotional directions, the negative, and now the positive."

There was significantly less response in the brains of the sleepers.

"When functioning correctly, the brain finds the sweet spot on the mood spectrum," Walker said. "But the sleep-deprived brain will swing to both extremes, neither of which is optimal for making wise decisions."

Too little of it can make us cranky, difficult, and, it now seems, giddy.

Copyright 2011 ABC News Radio

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