Deep sleep gives a deep cleaning to your brain
A new study has observed for the first time that cerebrospinal fluid washes in waves during sleep in and out of the brain, helping to clear up waste.
During sleep, immune cells are more active in the brain, engaged in maintenance work.
Researchers know that sleep is important — not only to allow the brain to reactualize, as well as to make space for “cleaning” processes to take place..
Many of the mechanisms by which brain waste clearing takes place during sleep, however, remain unclear.
Researchers at Boston University in Massachusetts have now found that the fluid in the brain and spinal cord called the cerebrospinal fluid washes in and out like waves during sleep, helping the brain to get rid of accumulated metabolic “trash.”
“We’ve known for a while that that there are there are these electrical activity waves in the neurons, but we haven’t realized before that there are waves in the cerebrospinal fluid, too,” says Laura Lewis, co-author of the study.
The new study — whose results appear in the Science journal — involved 13 participants between the ages of 23 and 33 who decided to undergo brain scans while they were asleep.
They seen that cerebrospinal fluid appears to “synchronize” with brainwaves, which is likely to help remove brain waste. Such waste includes potentially toxic proteins that otherwise can form buildups that may impede information flow between neurons.
These findings could also shed new light on the underlying mechanisms in conditions like Alzheimer’s disease, where toxic protein plaques play a key role in memory loss and other cognitive impairments.
They also explain that normal aging can be linked to poorer brain self-cleaning. Human brains tend to generate fewer slow waves with age, which can reduce blood flow in the brain, as well as pulsations of the cerebrospinal fluid.
“We see how the neural change always appears to occur first, and then blood flows out of the head and then a wave of cerebrospinal fluid into the head,” Lewis says. She adds, however, that there are still many unknowns.
The team claims that they need less oxygen when neurons switch off during sleep, leading to blood drainage from the brain. This, in turn, means that pressure also drops in the brain, which means that the cerebrospinal fluid needs to increase so as to maintain normal pressure in the absence of blood.
Laura Lewis say’s “But that’s just one possibility. What are the causal links? Is one of these processes causing the others? Or is there some hidden force that is driving all of them?”


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