New research shows that a recently discovered mechanism that removes waste products from the brain is mainly active during sleep. A team, from University of Rochester Medical Center (URMC), write about their findings in Science.

Lead author Dr. Maiken Nedergaard, co-director of URMC’s Center for Translational Neuromedicine, says:

“This study shows that the brain has different functional states when asleep and when awake. 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.”

While more recent research shows sleep can help with storing and consolidating memory, this alone does not explain what is happening.

From a survival point of view, sleep is rife with risk – all creatures are at their most vulnerable during sleep, especially when predators are around. Lack of sleep is also a real problem for the tired and weary.

In 2012, Nedergaard and colleagues reported that by using new imaging technology on mice, they had discovered a previously unrecognized system that drains accumulated by products of metabolism from the brain. In a paper published in Science Translational Medicine they called  this the “glymphatic system,” because it acts like the body’s lymphatic system but is managed by brain cells known as glial cells.In this study, the team conducted a series of new experiments on mice and found that the glymphatic system is nearly 10 times more active during sleep. They also noted that the sleeping brain removes significantly more amounts of one toxic protein, amyloid-beta, which is implicated in Alzheimer’s disease.