Science: do our brains clean themselves when we sleep?

February 13, 2020 / BIOON / -- a new study from Boston University shows that when you sleep at night, something wonderful happens to your brain Your neurons will be quiet In a few seconds, blood will come out of your head Then, a water-like fluid called cerebrospinal fluid (CSF) flows into the brain, washing your brain with rhythmic pulses The study, published in the journal Science, is the first to show that CSF pulses during sleep are closely related to brain wave activity and blood flow Photo source: https://cn.bing.com "we've known for a long time that neurons have these waves of activity," said study co-author Laura Lewis, assistant professor of Biomedical Engineering and faculty member of the center for systems neuroscience at Boston University School of engineering "But before that, we didn't realize that there were waves in the cerebrospinal fluid "This study may also be the first to take pictures of CSF during sleep Lewis hopes that one day, the study will give people a deeper understanding of a variety of neurological and psychological disorders that are often associated with sleep pattern disorders, including autism and Alzheimer's disease The coupling of EEG with blood flow and CSF can also provide information about age-related injury Early studies have shown that both CSF flow and slow wave activity help clear the brain of toxic, memory damaging proteins As people grow older, their brains produce fewer and fewer slow waves In turn, this will affect the blood flow of the brain, reduce the pulse of cerebrospinal fluid during sleep, and lead to the accumulation of toxic proteins and the decline of memory ability Although researchers tend to evaluate these processes individually, they now appear to be closely linked To further explore how aging affects blood flow and cerebrospinal fluid during sleep, Lewis and her team plan to enlist older people in their next study, which currently includes 13 subjects between the ages of 23 and 33 Lewis said they also hope to find a more sleep friendly method of cerebrospinal fluid imaging - wearing an EEG cap to measure their brain waves The first 13 subjects were asked to doze off in a noisy MRI machine, which is not easy for anyone who has done MRI to imagine "A lot of us are very excited to be involved because they want to be paid for their sleep," Lewis said But it turns out that this is almost the hardest part of our research We have all kinds of fancy equipment and complex technology, and usually a big problem is that people can't sleep because they are in a very noisy metal tube, which is a strange environment "But now, she's happy to have the opportunity to take pictures of CSF One of the most interesting results of the study, Lewis said, was that they could use a brain scan to check a small amount of cerebrospinal fluid to see if a person was sleeping "It's such a dramatic effect," she said "(cerebrospinal fluid pulse during sleep) is something that we don't know happened at all Now we just need to look at an area of the brain, and we can immediately read a person's brain state "As the research continues, Lewis's team wants to solve another problem: how do our brain waves, blood flow and cerebrospinal fluid coordinate so perfectly? "We do see that changes in the nervous system always seem to occur first, then blood flows out of the head, and then CSF goes into the head," Lewis said "One explanation might be that when neurons shut down, they don't need as much oxygen, so the blood leaves the area When the blood leaves, the pressure in the brain drops and the cerebrospinal fluid flows in quickly, maintaining the pressure at a safe level "But it's just a possibility," Lewis said "What is causation? Is one of these processes leading to the others? Or is there some hidden force driving them? These are all the questions we want to make clear, "reference: N.E fultz El Al., coupled electronic, hemodynamic, and cererospinal fluid situations in human sleep," science 01 Nov 2019: Vol 366, issue 6465, pp 628-631 doi: 10.1126/science.aax5440