Your Brain Never Sleeps

When you sleep, your brain burns nearly as much energy as when you are awake. It spends the night replaying the day at high speed, strengthening the neural connections worth keeping and pruning the ones it no longer needs. In effect, your brain edits your memories while you rest, deciding what stays and what fades.

The glymphatic system switches on mainly during sleep, flushing waste products out of brain tissue. As you sleep, the tiny gaps between brain cells widen by roughly 60 percent, letting cerebrospinal fluid flow through and wash away built-up debris such as amyloid plaques linked to Alzheimer's.