Sleep 'Detoxes' The Brain, New Research Suggests
Sleep 'Detoxes' The Brain, New Research Suggests
When you sleep, your brain undergoes a mop-up process that removes waste products linked to Alzheimer’s and dementia, according to new research published yesterday in the online version of Science.
A team of researchers at the University of Rochester Medical Center (URMC) used high-tech imaging to look deep into the brains of mice and discovered that the brain functions differently while asleep than awake, ridding itself of accumulated proteins at a much faster rate. (In mice, that is – but researchers use mouse brains because they’re considered surprisingly similar to human brains.)
Led by Maiken Nedergaard, M.D., who co-directs the URMC’s Center for Translational Neuromedicine, the researchers discovered that a waste-draining system they call the “glymphatic system” is ten times more active during sleep than while awake. This nocturnal cleaning system removes proteins called amyloid-beta, which accumulate into the plaques that contribute to Alzheimer’s disease and dementia.
Nedergaard and her team coined the term “glymphatic system” last year, when they used new imaging technology known as two-photon microscopy to discover a scrubbing process taking place around brain cells, known as glial cells. The mechanism of this cleanup process is fascinating: Nedergaard and colleagues found that cerebrospinal fluid flows through the spaces between neurons, flushing proteins and other neural waste into the circulatory system and away.
In this year’s research, they discovered that not only does the “glymphatic system” kick into high gear only during sleep, but it also mops up significantly more of the toxic protein amyloid-beta, considered a primary culprit in Alzheimer’s disease. Again using two-photon microscopy, the researchers looked at the timing of this flushing process and discovered that brain cells contract noticeably during sleep, thus expanding the areas between brain cells by as much as 60 percent. With brain cells smaller and the space between them larger, there’s more room for the cerebrospinal fluid to move freely.
Likening the changes during sleep to “turning on a faucet,” Nedergaard says it appears that a sleep state is necessary for this “active clearance of the by-products of neural activity” to take place. This would offer a convincing explanation of why sleep has such an essential restorative function, she says.
The discovery of the brain’s nocturnal cleaning service, coupled with previous research out of Washington University showing that levels of beta-amyloid drop during sleep, could open up new avenues of prevention and treatment for Alzheimer’s and dementia, experts say. Previous research found that depriving mice of sleep led to accumulation of amyloid-beta protein, also in mice. A few years ago, a New York Times report suggested that new insights into how some people’s brains hold on to beta-amyloid plaques more than others offered new hope for Alzheimer’s disease breakthroughs.
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