A new study suggests that the brain chemical dopamine - associated with pleasure and reward - can make the brain feel wired and tired even though the body is exhausted by missing a night's sleep.

In the research, mild and acute sleep deprivation was induced in mice before an analysis of their behaviour and brain activity revealed that the rodents were in a bubbly mood for a number of days after missing out on rest.

Study author Professor Yevgenia Kozorovitskiy, of Northwestern University, said: "Chronic sleep loss is well studied, and its uniformly detrimental effects are widely documented.

"But brief sleep loss - like the equivalent of a student pulling an all-nighter before an exam - is less understood.

"We found that sleep loss induces a potent antidepressant effect and rewires the brain.

"This is an important reminder of how our casual activities, such as a sleepless night, can fundamentally alter the brain in as little as a few hours."

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