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TUCKERED OUTA brain chemical called dopamine can help you stay alert even when you feel tired. Some people's brains are better at this than others letting them perform well on tests and pick up new information even after staying up all night. Science still shows though that learning and test-taking are best done after a good night's sleep.sjlocke / iStockphoto.com

When the school year starts, it can be tough to switch from lazy summer mornings to the blaring buzz of an alarm clock. After a few early mornings, extreme fatigue might make you feel like you’re going to fall over. The amazing thing is that you probably manage to stay awake all day long and into the night. But how?

A chemical in the brain called dopamine might be part of the answer. According to new research, dopamine is what keeps people who don’t get enough sleep from conking out. The chemical also has a complicated influence on your ability to think and learn when you don’t get enough zzzzz’s.

To study sleep loss and its effect on the brain, scientists from the National Institutes of Health in Bethesda, Md., and the Brookhaven National Laboratory in Upton, N.Y., rounded up 15 healthy volunteers. The scientists tested each person’s memory and ability to pay attention twice: once after a good night’s sleep and once after being kept up all night long. During the tests, the scientists measured levels of dopamine in the brains of the volunteers.

The results showed that when the volunteers stayed up all night, dopamine levels increased in two parts of the brain: the striatum and the thalamus. The striatum responds to motivations and rewards. The thalamus controls how alert you feel.

Higher levels of dopamine, the study suggested, kept the volunteers awake even though they felt tired.

In addition, the new research suggests that dopamine levels might play a part in controlling how well people can function without sleep.

Some people are miraculously able to think clearly and react quickly, even when they haven’t had much sleep. Other people have a really hard time paying attention when exhausted, and their reaction times slow way down. The researchers found that higher levels of dopamine don’t fend off the trouble people have thinking and learning while sleep-deprived. But the new research does suggest that dopamine levels may play a part in controlling how well people can function without sleep.

Dopamine is a complicated chemical, and sleep-deprivation is a complicated state of mind. Even when people think they feel OK, exhaustion makes it difficult for them to learn or think as well as they can when they’re rested.

“A little bit of dopamine is good,” says Paul Shaw, a sleep researcher at Washington University in St. Louis. “More is bad. Less is bad too. You’ve got to be in the sweet spot,” to think, respond and learn to your full potential.

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