Not every dream is the same when it comes to cleansing the brain


Posted 28/02/2019 8:05:34CET

MADRID, Feb 28 (Europa Press)

New research shows how deep sleep can affect our brain's ability to effectively eliminate toxic waste and protein. As sleep often becomes lighter and more disturbed as we get older, the study reinforces and potentially explains the links between aging, lack of sleep, and increased risk of Alzheimer's disease.

"Sleep is fundamental to the function of the brain's waste disposal system and this study shows that the deeper the dream, the better"says lead author Maiken Nedergaard, co-director of the Center for Translational Neuromedicine at the University of Rochester Medical Center (URMC) in New York, United States. These results also provide increasingly clear evidence that sleep quality or lack of sleep can predict the onset of Alzheimer's disease and dementia, "he adds.

The study, published in the journal Science Advances, indicates that slow and steady cardiopulmonary activity associated with non-REM deep sleep is ideal for the function of the glyph system, the brain's exclusive process for eliminating waste. The results may also explain why some forms of anesthesia may lead to cognitive decline in older adults.

The previously unknown glyph system was first described by Nedergaard and his colleagues in 2012. Prior to this, scientists did not fully understand how the brain, which maintains its own closed ecosystem, eliminated waste. The study revealed a tubing system that accumulates in the blood vessels and pumps the cerebrospinal fluid (CSF) through the brain tissue to remove the waste. Later work has shown that this system works mainly while we sleep.


As the accumulation of toxic proteins, such as beta-amyloid and tau in the brain, is associated with Alzheimer's disease, the researchers speculated that deterioration of the glyphic system by disruption of sleep could be a major determinant of the disease. This fits into the clinical observations that show an association between sleep deprivation and an increased risk of Alzheimer's.

In the present study, the scientists performed experiments on mice that were anesthetized with six different anesthetic regimens. While the animals were under anesthesia, the researchers tracked the brain's electrical activity, cardiovascular activity, and CSF clearance flow through the brain. The team observed that a combination of ketamine and xylazine (K / X) drugs more closely mimicked slow and steady electrical activity in the brain and slow heart rate associated with non-REM deep sleep. In addition, the electrical activity in rodent brains, given K / X, appeared to be ideal for the function of the glyph system.

"Synchronized waves of neural activity during deep slow-wave sleep, specifically the activation patterns that move from the front of the brain to the back, coincide with what we know about the flow of cerebrospinal fluid in the glyph system," says the first author of the study, Lauren Hablitz, associate postdoctoral researcher at the Nedergaard laboratory. "It seems that the chemicals involved in the activation of neurons, that is, the ions, conduct a process of osmosis that helps extract the fluid through the brain tissue."

The study raises several important clinical issues. It also strengthens the link between sleep, aging and Alzheimer's disease. It is known that as we age, it becomes more difficult to achieve non-REM deep sleep constantly, and the analysis supports the importance of deep sleep for proper functioning of the glyph system.

The study also shows that the glyphic system can be manipulated by improving sleep, a finding that may point to possible clinical approaches such as sleep therapy or other methods to improve sleep quality for populations at risk.

Besides that, since several of the compounds used in the study were analogous to anesthetics used in clinical settingsThe study also sheds light on the cognitive difficulties that older patients frequently experience after surgery and suggests classes of medications that could be used to prevent this phenomenon. Rodents in the study who were exposed to anesthetics that did not induce slow brain activity decreased glomus activity.

"Cognitive impairment following anesthesia and surgery is a major problem," says study co-author Tuomas Lilius of the Center for Translational Neuromedicine at the University of Copenhagen in Denmark. A significant percentage of elderly patients who undergo surgery experience a postoperative period of delirium or have a new or aggravated cognitive impairment at discharge. "


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