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Sleep is important for the breakdown of pollutants in the brain
A recent study provides an understanding of how our bodies remove toxins from our brains during sleep. In the future, this could open up new ways of treating and preventing neurodegenerative diseases such as Alzheimer's.
The current study at Boston University found how the body can break down toxins in the brain during sleep. The results of the study were published in the English-language journal "Science".
Toxins are removed from the brain during sleep
When we sleep, our brain goes through various phases, from light sleep to deep sleep to REM sleep (Rapid Eye Movement). An important 2013 study in mice showed that toxins such as beta-amyloid were removed during rodent sleep. In their current study, the researchers wanted to find out how these toxins were excreted and why this process only took place during sleep.
How did the study work?
The participants slept in an MRI machine. To get realistic sleep cycles, the tests were run at midnight. The participants wore a so-called EEG cap so that electrical currents can be recorded in the brain. It was thus possible to determine the stage of sleep the people were in. MRI was also used to show how much cerebrospinal fluid (CSF) flows in and out of the brain.
What happens in the brain during sleep?
Large, slow waves of cerebrospinal fluid washed over the brain during non-REM sleep. The EEG values helped to show why this is so. During non-REM sleep, the neurons start to synchronize and they turn on and off at the same time. Since the neurons all stopped firing for a short time, they no longer needed as much oxygen. This resulted in less blood flowing to the brain. Liquor could so enter and fill the space left behind.
Sleep is not just for relaxation
The electrical activity of the brain can move fluid, this was an extremely interesting finding, the researchers report. The systems responsible for this are of great importance both in mice and in humans. Sleep is not only a means of rest and relaxation, sleep has a completely different function: Because so many neurons switch off at the same time - which would not be possible when awake - the amount of blood in the brain drops so much that larger amounts of cerebrospinal fluid circulate around the brain and metabolic by-products can be eliminated.
Do the results make treatment for Alzheimer's possible?
The study could open up clinical applications for the treatment of Alzheimer's. Recent attempts to develop drugs target beta amyloid. But drugs that initially looked promising failed when they entered clinical trials. Instead of trying to act on a particular molecule, new interventions could instead focus on increasing the amount of cerebrospinal fluid. In this way harmful substances could be removed better. (as)
Author and source information
This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
- Nina E. Fultz, Giorgio Bonmassar, Kawin Setsompop, Robert A. Stickgold, Bruce R. Rosen et al .: Coupled electrophysiological, hemodynamic, and cerebrospinal fluid oscillations in human sleep, in Science (query: 01.11.2019), Science