It's no wonder we feel refreshed after a good night's sleep — scientists have discovered that our brains have a self-cleaning mechanism that clears toxins when we're snoozing.
It turns out the glymphatic system kicks into action when we're sleeping to pump cerebral spinal fluid through our brain cells to flush out toxic by-products that build when we're awake. It then sends them to the liver to be eliminated.
Using two-photon microscopy, a new brain imaging technique that allows scientists to see deep inside tissue, University of Rochester researchers observed mice brains, which are similar to human brains.
They found that during sleep, brain cells contract to increase the space between them so that spinal fluid can wash freely through the tissue.
"We have a cleaning system that almost stops when we are awake and starts when we sleep. It's almost like opening and closing a faucet — it's that dramatic," said lead author Dr Maiken Nedergaard.
"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."
Now the researchers are hopeful that their findings could pave the way for new treatments for brain diseases, such as Alzheimer's, because patients get a build-up of the protein amyloid beta, which forms plaques on the brain.
Nedergaard is trialling drugs in mice to increase the brain's cleaning function.
"Understanding how and when the brain activates the glymphatic system and clears waste is a critical first step in efforts to potentially modulate the system and make it work more efficiently," she said.
They found the glymphatic system is about 10 times more active during sleep than when awake.
The study was published in the journal Science.