Scientists have tested the effect of pink noise on the protective processes of the brain
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- Scientists have tested the effect of pink noise on the protective processes of the brain
Researchers at the Massachusetts Institute of Technology have discovered a way to amplify waves of cerebrospinal fluid during sleep using short sound pulses. Correctly synchronized bursts of so-called pink noise amplified slow waves of brain activity, followed by an increased flow of fluid involved in the removal of waste products of nerve cells. About how sound can affect the natural process of cleansing the brain during sleep and how the discovery may be useful in the future, see the "Izvestia" material.
Pink noise was synchronized with brain activity
The results are published in the journal Science Translational Medicine (STM). During the experiment, experts tested whether it is possible to amplify the waves of cerebrospinal fluid with the help of sound effects — a transparent liquid that surrounds the brain and spinal cord, protects them and participates in the removal of waste generated during the work of nerve cells.
To do this, the scientists used short pulses of pink noise lasting 50 ms. It looks like white noise, but the low frequencies in it sound stronger than the high ones, so such a signal is perceived as a soft, uniform sound, reminiscent of the sound of rain or a distant waterfall. Unlike the constant background noise, the researchers sent impulses only at a certain moment — at the peak of slow waves of electrical activity in the brain.
Laura Lewis, senior author of the study
You can generate more of these slow electrical waves with an auditory stimulus if it arrives at the right moment. Like a child on a swing: if you push him at the right moment of movement, you can swing the swing further.
To determine this moment, participants simultaneously recorded brain activity using EEG and monitored the movement of cerebrospinal fluid using functional MRI. The magnetic field of the tomograph interferes with the EEG, so the researchers developed a system that removed them in less than 100 ms. An additional algorithm predicted the approach of the slow wave peak and allowed the sound pulse to be turned on in time.
How the brain gets rid of waste during sleep
The study involved 14 healthy volunteers. The sound pulses were not loud enough to wake a person up, but after they were delivered, the amplitude of the slow electrical brain waves increased. At the same time, the waves of movement of the cerebrospinal fluid became stronger. Thus, scientists have managed to influence the sleep-related process, which was previously mainly observed as a natural part of the brain.
The connection between slow waves and fluid movement is especially important. They occur during slow-wave sleep, and become more pronounced as it deepens. According to MRI data, slow waves cause the blood vessels of the brain to alternately constrict and expand. Due to this, they work as a kind of pump that promotes the movement of cerebrospinal fluid through the brain.
Cerebrospinal fluid helps to remove waste products from nerve cells that accumulate during the day. Among them are molecules and proteins formed during the brain's work. Therefore, a full sleep is considered not only as a rest period, but also as a time when the processes of maintaining the normal state of the nervous system are activated.
Laura Lewis
We have found that we can increase the amplitude of the wave of cerebrospinal fluid flow during sleep, which, as far as we know, has not been achieved by any method before. Now that we can enhance the flow of cerebrospinal fluid during sleep in healthy adults, we are very excited to introduce this technology into clinical practice to see what results we can achieve.
How the discovery can help in the future
The authors of the study do not yet claim that pink noise can improve memory, prevent dementia, or treat sleep disorders. The experiment was conducted on a small group of healthy adults in the laboratory, so the results should be verified in further studies. In the next step, the scientists want to find out whether increasing the flow of cerebrospinal fluid can actually improve sleep recovery and cognitive function.
Researchers are also interested in the potential connection of the method with neurodegenerative diseases. In Alzheimer's disease and some other similar conditions, abnormal proteins accumulate in the brain, including amyloid and tau. Therefore, scientists want to test whether strengthening the natural waste disposal process can affect the accumulation of such substances in the future. However, a new study does not show this yet.
Joshua Levitt, lead author of the study
Removing waste from the brain is of great importance in Alzheimer's disease and other forms of dementia, which are partly caused by the accumulation of molecules such as amyloid and tau protein in the brain. If we can improve waste removal from the brain, we may be able to help prevent the accumulation of these plaques that lead to disease.
Levitt has already started work on a potential device that could provide a sound stimulus at the right moment of sleep and thereby enhance the flow of cerebrospinal fluid. In the future, the researchers plan to test the approach on people with sleep disorders and other diseases. So far, the results only show that a precisely calculated sound pulse is capable of amplifying sleep-related brain waves and the movement of cerebrospinal fluid.
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