Yet something clearly goes terribly wrong. Researchers have known for more than a decade that a rat prevented from sleeping will lose the ability to maintain body heat and die in about three weeks, leaving no clues in the form of physiological damage. For humans, sleep deprivation undermines thinking, but science has no explanation. Sleepers lower their metabolic rate, thereby conserving energy. But this does not explain why we lose consciousness.
Most researchers believe sleep benefits the brain, perhaps by giving neurons a chance to recuperate.
Although it is too soon to proclaim the conundrum of sleep solved, findings are illuminating processes that seem to control it. At the same time, investigators are refining their ideas about the benefits of slumber for the brain. Understanding its purposes may ultimately help the millions of people who suffer from sleep disorders, which range in severity from the merely irritating to the fatal. The starting point for many investigations into the control of sleep has been the hypothalamus, a platformlike structure in the brain that has long been known to have an important role. Damage to the back part of the hypothalamus causes somnolence, suggesting that when intact, it maintains alertness.