"Sleep is critical to the function of the brain's waste removal system and this study shows that the deeper the sleep the better," said Maiken Nedergaard, M.D., D.M.Sc., co-director of the Center for Translational Neuromedicine at the University of Rochester Medical Center (URMC) and lead author of the study. "These findings also add to the increasingly clear evidence that quality of sleep or sleep deprivation can predict the onset of Alzheimer's and dementia."
The study, which appears in the journal Science Advances, indicates that the slow and steady brain and cardiopulmonary activity associated with deep non-REM sleep are optimal for the function of the glymphatic system, the brain's unique process of removing waste. The findings may also explain why some forms of anesthesia can lead to cognitive impairment in older adults.
System - Nedergaard - Colleagues - Point - Scientists
The previously unknown glymphatic system was first described by Nedergaard and her colleagues in 2012. Prior to that point, scientists did not fully understand how the brain, which maintains its own closed ecosystem, removed waste. The study revealed a system of plumbing which piggybacks on blood vessels and pumps cerebral spinal fluid (CSF) through brain tissue to wash away waste. A subsequent study showed that this system primarily works while we sleep.
Because the accumulation of toxic proteins such as beta amyloid and tau in the brain are associated with Alzheimer's disease, researchers have speculated that impairment of the glymphatic system due to disrupted sleep could be a driver of the disease. This squares with clinical observations which show an association between sleep deprivation and heightened risk for Alzheimer's.
Study - Researchers - Experiments - Mice - Regimens
In the current study, researchers conducted experiments with mice that were anesthetized with six different anesthetic regimens. While the animals were under anesthesia, the researchers tracked brain electrical activity, cardiovascular activity, and the cleansing flow of CSF through the brain. The team observed that...
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