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Wednesday, 25 April, 2001, 18:37 GMT 19:37 UK
Sleep 'helps brain work'
Brain scan
Sleep is linked to the memory process
Scientists have shown just what an important role sleep plays in the effective functioning of the brain.

The US study was carried out on cats, but it could have implications for humans wanting to improve their ability to learn and remember.

Students suffering revision nightmares would be better off getting a good night's sleep than opting for late-night cramming sessions, according to the team at the University of California in San Francisco (UCSF).

If you reviewed your notes and then slept, you'd achieve as much ... as if you'd pulled an all-nighter

Prof Michael Stryker
The researchers found sleep dramatically improves the way changes take place in the connections between nerve cells in the brain.

These changes underpin the brain's control of behaviour, learning and memory.

The study measured changes in the brains of cats while they had one eye covered for six hours.

Consolidating experience

The brains of those cats allowed to sleep for six hours after the challenge showed more change and adaptation than those not allowed to sleep.

The researchers believe the findings provide strong evidence sleep helps the brain function well and consolidate experience into memory in animals.

They maintain the study has implications for the human brain, including how we prepare for exams.

Cats' brains adapted better with sleep
Researcher Professor Michael Stryker said: "The [study] suggests that if you reviewed your notes thoroughly until you were tired and then slept, you'd achieve as much plasticity, or 'learning,' in the brain as if you'd pulled an all-nighter repeating your review of the material."

Researchers also found changes in the brain were linked to deep sleep rather than "dream sleep" associated with rapid eye movement (REM).

Evidence that sleep plays a significant part in brain development will help researchers solve the mystery of why we sleep.

Sleep mystery

Dr Marcos Frank, the lead researcher, said: "Every animal sleeps - even flies may have a state like sleep.

"But despite our understanding of the consequences of sleep loss on human performance, why the brain needs sleep has remained a mystery."

Prof Stryker added: "Speculation has ranged from evolutionary theories - we need sleep to prevent us from wandering out of our caves in the dark or keeping us inactive when goblins or sabre tooth tigers are out - to theories having to do with the function of neural networks."

Researchers know that in early development birds and mammals, including humans, sleep as much as three times as long as adult birds and mammals.

Previous studies in humans have shown that sleep and sleep loss influence learning and memory.

The research is published in the medical journal Neuron.

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