Scientists have just reported the first major mechanical reason our brains need to sleep — certain cleaning mechanisms in the brain work better when we shut the brain down. Just like how dump trucks take to the city streets during the pre-dawn hours because there's less traffic, our brain's cleaners also work best when there's less going on.
"This study shows that the brain has different functional states when asleep and when awake," study researcher Maiken Nedergaard, of the University of Rochester said in a statement. "In fact, the restorative nature of sleep appears to be the result of the active clearance of the by-products of neural activity that accumulate during wakefulness."
We've known that our brains consolidate memories during sleep and perform other important functions.