The brain needs to flush out waste products to stay healthy and fend off conditions like Alzheimer’s disease. Scientists are beginning to understand how the the brain’s waste removal system works.
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A MARTÍNEZ, HOST:
Turns out the brain needs regular cleaning. Otherwise, it gets clogged up with waste products, including some associated with diseases such as Alzheimer’s and Parkinson’s. NPR’s Jon Hamilton reports that scientists are finally figuring out just how the brain cleans itself.
JON HAMILTON: In most of the body, waste disposal is pretty simple. Jonathan Kipnis of Washington University in St. Louis says the system is a lot like what you’d find in a home.
JONATHAN KIPNIS: You have the water pipes and the sewage pipes. Water comes in clean, and then you wash your hands and then the dirty water goes down.
HAMILTON: Into the sink and down the drain. In the body, this process relies on the lymphatic system, a network of tubes connected to the bloodstream. But that system doesn’t extend to the brain. So Kipnis says scientists had a question.
KIPNIS: How does the dirt molecule – let’s assume there is a waste molecule from the middle of the brain will make all the way out to the borders of the brain into the brain’s sink?
HAMILTON: Part of the answer came in 2012 and 2013. A team led by a Danish scientist found evidence that during sleep, cerebrospinal fluid flowed quickly through the brain, flushing out waste. But what was pushing the fluid? Kipnis and his team began looking at what the brain was doing as it slept. As part of that effort, they measured the power of a slow electrical wave that appears during deep sleep. And, he says, they realized something.
KIPNIS: By measuring the wave, we are measuring also the flow of interstitial fluid.