Vol. 342 no. 6165 pp. 1440-1441
To Sleep, Perchance to Clean
In work that Science‘s editors named a runner-up for Breakthrough of the Year, researchers studying mice have found experimental evidence that sleep helps to restore and repair the brain.
Why do we sleep?
Questions of biology don’t get much more fundamental than that. This year, neuroscientists took what looks like a major stride toward an answer.
Most researchers agree that sleep serves many purposes, such as bolstering the immune system and consolidating memories, but they have long sought a “core” function common to species that sleep. By tracking colored dye through the brains of sleeping mice, scientists got what they think is a direct view of sleep’s basic purpose: cleaning the brain. When mice slumber, they found, a network of transport channels through the brain expands by 60%, increasing the flow of cerebral spinal fluid. The surge of fluid clears away metabolic waste products such as β amyloid proteins, which can plaster neurons with plaques and are associated with Alzheimer’s disease.
Until this discovery, researchers thought the brain’s only way to dispose of cellular trash was to break it down and recycle it inside cells. If future research finds that many other species undergo this cerebral housekeeping, it would suggest that cleaning is indeed a core function of sleep. The new findings also suggest that sleep deprivation may play a role in the development of neurological diseases. But with a causal role far from certain, it’s too early for anyone to stay awake worrying.
References and Web Sites
E. Underwood, “Sleep: The Brain’s Housekeeper?” Science 342, 6156 (18 October 2013).
L. Xie et al., “Sleep Drives Metabolite Clearance From the Adult Brain,”Science 342, 6156 (18 October 2013).