BBC opens our eyes to a hidden process in the night, when sleep washes away toxic proteins in your brain:
Scientists, who imaged the brains of mice, showed that the glymphatic system became 10-times more active when the mice were asleep.
Cells in the brain, probably the glial cells which keep nerve cells alive, shrink during sleep. This increases the size of the interstitial space, the gaps between brain tissue, allowing more fluid to be pumped in and wash the toxins away.
Dr [Maiken] Nedergaard [of University of Rochester Medical Center] said this was a “vital” function for staying alive, but did not appear to be possible while the mind was awake.
Their next step appears to be to put humans into an MRI and watch them sleep.