While the brain sleeps, it clears out harmful toxins, a process that may reduce the risk of Alzheimer's, researchers say.
During sleep, the flow of cerebrospinal fluid in the brain increases dramatically, washing away harmful waste proteins that build up between brain cells during waking hours, a study of mice found.
"It's like a dishwasher," says Dr. Maiken Nedergaard, a professor of neurosurgery at the University of Rochester and an author of the study in Science.
The results appear to offer the best explanation yet of why animals and people need sleep. If this proves to be true in humans as well, it could help explain a mysterious association between sleep disorders and brain diseases, including Alzheimer's.
Nedergaard and a team of scientists discovered the cleaning process while studying the brains of sleeping mice.