Even the most gifted scientist on the planet cannot explain why people sleep. Fifty years of intensive research have yielded a variety of intriguing leads. But researchers who bragged, at a conference in the 1970s, that the secret of sleep would be theirs by the millennium have had to revise their estimates. ‘‘We were too optimistic,’’ said Dr Michel Jouvet, a professor emeritus at Claude Bernard University in Lyon, France, who attended that meet. The discovery of rapid eye movement (REM) sleep in 1953 awakened scientists to the realisation that sleep was not ‘‘a simple turning off of the brain’’, but an active, organised physiological process, said Dr Jerome Siegel, a professor of psychiatry and bio-behavioural sciences at the University of California. Five decades later, few would dispute that sleep serves some critical—if unknown—purpose. What is it about sleep that makes it essential? Experts say it’s not simply the fact that humans need rest. Another theory holds that sleep may serve to protect animals, by taking them out of circulation during the dangerous hours when predators roam. Yet this theory, some experts point out, cannot explain why the sleep winks lost one night are made up the next or why the impact of long-term sleep deprivation is so severe. The most promising theory so far proposes that REM sleep plays a role in brain development. Newborns spend more time in REM than adults. Animals that spend long periods in REM are also more immature at birth. In the meantime, the search continues. The New York Times News Service
