The rhythmic waves of blood and cerebrospinal fluid (CSF) that occur when we are sleeping, appear to function much like a washing machine’s rinse cycle, which may help to clear the brain of toxic waste on a regular basis.

Laura Sanders, Science News »

Every 20 seconds, a wave of fresh cerebrospinal fluid rolls into the sleeping brain. These slow, rhythmic blasts, described for the first time in the Nov. 1 Science, may help explain why sleep is so important for brain health.

Studies on animals have shown that the fluid, called CSF, can wash harmful proteins, including those implicated in Alzheimer’s disease, out of the brain. The new results give heft to the idea that a similar power wash happens in sleeping people.

Dr. Francis Collins, NIH Director’s Blog »

The findings, published recently in the journal Science, are the first to suggest that the brain’s well-known ebb and flow of blood and electrical activity during sleep may also trigger cleansing waves of blood and CSF. While the experiments were conducted in healthy adults, further study of this phenomenon may help explain why poor sleep or loss of sleep has previously been associated with the spread of toxic proteins and worsening memory loss in people with Alzheimer’s disease.

From Science News via YouTube »

During non-REM sleep, oxygen-rich blood (colored red) flows out of the brain just before a wave of cerebrospinal fluid (blue) rolls in, entering from a lower part called the fourth ventricle. That cerebrospinal fluid may help clean harmful proteins out of the brain.