With some exceptions, humans and animals prefer to live in an environment free of filth. We clean our bodies and our homes so we can live healthy and productive lives. It turns out, the brain does too.
Researchers at the University of Rochester discovered that the brain cleans itself during sleep—explaining one of the major reasons we partake in a nightly ritual that has mystified scientists for centuries.
“Sleep has a critical function in ensuring metabolic homeostasis,” Dr. Maiken Nedergaard et al say in their paper published in Science. “The restorative function of sleep may be a consequence of the enhanced removal of potentially neurotoxic waste products that accumulate in the awake central nervous system.”
Instead of a lymphatic system, the brain has what the researchers call a “glymphatic system.” Waste products that build up during waking hours flush out through the membranes of glial cells in the brain’s interstitial space as cerebral spinal fluid (CSF) flows in. In the process, proteins like b-amyloid, which are associated with Alzheimer’s disease, are washed away. The exchange of fluids occurs along the brain’s vasculature; CSF flows in around arteries, while interstitial fluid (ISF) exits in the space around veins.