Preserved human brains have recently revealed the cause of narcolepsy to California researchers at UCLA and Stanford University. Narcolepsy  is a serious and sometimes dangerous sleep disorder that causes some people to fall asleep without warning.

The brains used in the study came from victims of narcolepsy. Before death, they donated their bodies to science. After death, researchers removed their brains and preserved them (that is, mummified them in some type of solution) to use for research.

Scientists then studied brain cells from the narcoleptic brains and compared them to cells from preserved brains of people who did not have the disease. They discovered that narcoleptics were missing special cells (that secrete orexin, a sleep-inducing hormone) from an area of the brain called the hypothalamus. They speculate that these cells may have been destroyed by some type of toxin or perhaps an autoimmune disorder.