Feeling a bit muddled after a sleepless night? It may be because your brain didn't get a chance to flush out built-up toxins, NPR reports. While we're asleep, the brain acts, in a researcher's words, "like a dishwasher"—at least in animals studied, including mice and baboons. Last year, the BBC notes, experts discovered a "plumbing" system in the brain. During sleep, it seems, it's working in overdrive, "pumping fluid into the brain and removing fluid from the brain in a very rapid pace," researcher Maiken Nedergaard says.
Mouse brain cells, the scientists found, contracted during sleep, and fluid was able to move between them more easily. Upon a mouse's waking, the cells expanded. Not only could the phenomenon explain why extensive sleep deprivation can kill—it may also teach us about an observed link between sleep disorders and Alzheimer's Disease, among other brain diseases. Beta amyloid, whose buildup is tied to the illness, is one of the chemicals the brain gets rid of while asleep.