A magnetic resonance imaging scan of an adult brain with cerebrospinal fluid overlaid in blue
Stephanie D. Williams (CC-BY 4.0)
The brain’s “waste disposal system” may be triggered after intense neural activity — and it may be possible to intentionally turn on the process.
Until recently, this system was thought to be activated only during sleep, but now researchers have observed it in people after viewing a flickering checkerboard pattern on a screen.
The finding provides a tantalizing clue that people may be able to intentionally clear out waste products from their brains by staring at intense visual stimuli, says Laura Lewis at Boston University in Massachusetts.
“The real surprise was that they found it in awake people,” says Edoardo Rosario de Natale at the University of Exeter in the UK, who was not involved in the work.
Cerebrospinal fluid (CSF) is pumped into the brain in the brain’s waste disposal system and released through a network of fine tubes called the glymphatic system, which was only discovered in 2012.
Animal research shows that the fluid flushes out waste products made by brain cells, including harmful compounds that may be involved in Alzheimer’s disease and Parkinson’s disease, such as beta-amyloid and alpha-synuclein.
Since the discovery of the glymphatic system, there has been an increase in research aimed at understanding how promoting fluid flow may improve brain health, but how the system functions in people is still unclear. .
Lewis’ team took advantage of a new brain-scanning technique using existing magnetic resonance imaging machines, which highlights any CSF that enters the brain’s fourth ventricle, a cavity at the base of the head. Fluid entering this chamber exits through the glymphatic system.
They asked 20 volunteers to watch a screen inside the scanner that displayed a pattern known to cause higher brain activity: a flickering black-and-white spiral checkerboard. Apart from short breaks, the display was switched on and off at 16-second intervals for approximately one hour.
When shown the pattern, it increased blood flow to the visual centers of the brain, as expected. When the screen went dark, blood flow decreased and CSF flow to the brain increased.
Brain-scanning techniques could not detect whether fluid was released through the glymphatic vessels, nor whether there was a decrease in waste products within the brain. These are questions that need to be tackled further, says Rosario de Natale. “It’s opening a new door.”
“It’s still an open question whether the fluid goes directly into the brain tissue or if it seeps into the ventricles. But we certainly think it has an effect on the fluid in the rest of the brain,” said the team. member says Stephanie WilliamsAlso at Boston University.
“We are now very interested in understanding the impact of these changes in fluid flow and how this intersects with brain health,” says Lewis.
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