Good to sleep your brains out

THE Bard knew the value of sleep. But how does this marvellous therapy work?

There are several theories. Giulio Tononi and Chiara Cirelli, professors of psychiatry at the University of Wisconsin-Madison, put forward a new one in the current edition of Scientific American. They want to turn accepted wisdom on its head.

All animals, even flies and cockroaches, sleep. Hibernators are out for the count all winter. Swifts and house-martins cat-nap on the wing. Falling asleep is risky; a predator can creep up on you, the house may go on fire or burglars may break in. Sleep must be essential to an animal’s welfare that it’s prepared to take such a risk.