A new US study found an additional benefit of sleep: It creates the right conditions to clean our brains from "metabolic trash."
The metabolic trash is formed by toxic proteins that if accumulated, could weaken the flow of information between neurons, causing a number of diseases such as Alzheimer's.
During the study, which was published recently in the Science journal, researchers at the Boston University have found that during sleep, the fluid present in the brain and spinal cord, called the cerebrospinal fluid, washes in and out, like waves, helping the brain get rid of accumulated metabolic "trash."
Before this study, scientists thought that the benefits of this colorless liquid are limited to the protection of the brain, as it provides a protective layer that protects the brain inside the skull and contributes to the flow of cerebral blood.
In a report published on Saturday by the Medical News Today website, co-author Laura said: "We've known for a while that there are these electrical waves of activity in the neurons. But before now, we didn't realize that there are actually waves in the cerebrospinal fluid."
The new study included 13 participants aged 23–33 who agreed to undergo brain scans while asleep. The participants had to wear EEG caps that allowed the researchers to measure electrical activity in their brains while lying in an MRI machine.
"However, sleeping in this location can be difficult, as MRI machines are very noisy. It turns out that the participants' job is actually almost the hardest part of our study. Despite these challenges, the researchers managed, probably for the first time, to monitor the activity of cerebrospinal fluid in the participants' brains during sleep," noted Lewis.
They saw that cerebrospinal fluid appears to "synchronize" with brainwaves, which likely helps remove brain waste.
Although the study linked sleep to the cerebrospinal fluid, these findings, Lewis adds, could also shed fresh light on the underlying mechanisms in conditions such as Alzheimer's disease, in which toxic protein plaques play a key role in memory loss and other cognitive impairments.