Here is an excerpt from an article posted by Thu-Huong Ha at the TED website. To read the complete article and watch the film of Russell Foster’s TED program, please click here.

Photo: James Duncan Davidson

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Neuroscientist Russell Foster opens a session of TEDGlobal all about … us, asking the question: Why do we sleep? Thirty-six percent of our lives are spent asleep, which means, if you live to 90, you’ll have slept for 32 years. But we don’t appreciate sleep enough, says Foster. He quotes Thomas Edison — “Sleep is a criminal waste of time, inherited from our cave days” — and Margaret Thatcher — “Sleep is for wimps.” Simply put, says Foster, not only do we not appreciate sleep, but we treat it like an illness and an enemy.

Of course this simply shouldn’t be the case. In fact, some areas of the brain are more active during the sleep stage than while the body is awake. But the essential question that we — ahem — lose sleep over: Why do we sleep? There is no real consensus, but Foster gives three popular answers:

1. Sleep is for restoration, to replenish and repair metabolic processes. Indeed, a whole host of genes are “turned on” only during sleep — genes associated with restoration and metabolic pathways.

2. Sleep is for energy conservation, to save calories. This may seem an intuitive answer, says Foster, except that the difference between sleeping and quietly resting is about 110 calories a night, the equivalent of a hot dog bun. Not a very good upshot for such a complex process.

3. Finally, sleep is for brain processing and memory consolidation. This is the explanation Foster espouses. Studies show that if you prevent people from sleeping after a learning task, their ability to learn is basically smashed. And worse, our abilities to come up with novel solutions after a complex task are reduced after sleep deprivation.

The danger of sleep deprivation can’t be stressed enough. For one thing, sleep-deprived people fall asleep involuntarily, taking “microsleeps” they can’t control. Thirty-one percent of drivers, says Foster, will fall asleep while driving at least once in their lifetime. That is: 100,000 accidents a year happen because of tiredness.

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To read the complete article and watch the film of Russell Foster’s program, please click here.

Russell Grant Foster, FRS (born circa 1959) is a British professor of circadian neuroscience, currently based at Brasenose College at the University of Oxford. He and his group are credited with the discovery of the non-rod, non-cone, photosensitive ganglion cells in the mammalian retina which provide input to the circadian rhythm system. Foster was elected a fellow of the Royal Society in 2008 and a member of the Biotechnology and Biological Sciences Research Council in 2011. To check out Sleep: A Very Short Introduction, a book Russell co-authored with Steven W. Lockley, please click here.