We know that getting even a measly extra hour of sleep a night can have major benefits for us—like more memories, less anxiety, and happier genes. But scientists have tested another hypothesis for why we need to spend so much time horizontal: Sleep cleans our brains.
Ian Sample, the appropriately named science writer for the Guardian, summarizes the phenomenon this way:
Through a series of experiments on mice, the researchers showed that during sleep, cerebral spinal fluid is pumped around the brain, and flushes out waste products like a biological dishwasher.
The process helps to remove the molecular detritus that brain cells churn out as part of their natural activity, along with toxic proteins that can lead to dementia when they build up in the brain, the researchers say.
We might want to take these conclusions with a grain of cerebral salt, given that human brains are more mightily complex than those of mice. Still, the results are super fascinating. As published in the journal Science, University of Rochester professor Maiken Nedergaard led a team that found out that the brain cells of mice shrink while they sleep—creating a space between them that's 60% bigger, which allows for the cerebral spinal fluid in their brains to flow 10 times faster while sleeping than while waking.
Then they wanted to see how the mice brains did with toxins, so they injected them with proteins associated with Alzheimer's disease—and found the proteins were cleaned up faster in the brains of sleeping mice.
This is super fascinating because we've known about the effects of better sleep, like the memory consolidation that we need to remember our lives, but Nedergaard's research sheds light on the actual mechanics of what's happening while we're not waking. If the same holds true for humans, then sleep may be a key to fighting dementia and other degenerative diseases, since it's the time that your brain sweeps clean the toxins that are laying about.
"You can think of it like having a house party," Nedergaard said in a statement. "You can either entertain the guests or clean up the house, but you can't really do both at the same time."
Hat tip: the Guardian.com