Insufficient, restless sleep can impair memory and judgement, and also lead to increased risk of medical conditions such as stroke, obesity and cardiovascular disease, scientists warn.
"Sleep is even more multifaceted and fascinating than we realise," said Sigrid Veasey, from the University of Pennsylvania in the US.
"The findings reveal interesting new aspects of the complex relationship between sleep and the brain, and the vital role that sleep plays in everyday human functioning," said Veasey.
MicroRNA expression may serve as an indicator of sleep loss in rats and humans, suggesting a possible method for predicting those at risk for diseases and cognitive deficits typically associated with sleep debt, the scientists said.
They found that three species of spiders have amazingly fast circadian clocks, raising questions about how they avoid the negative effects typically associated with deviating from the normal biological time frame.
The brain preferentially reactivates negative memories during sleep, prioritising the retention of these emotional memories, they said.
A computerised algorithm can determine whether people viewed images of faces or houses by comparing patterns of electrical activity in the brain during sleep.
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