Scientists make waves in awake brains
Controlling spinal fluid might help treat neurological diseases.
Waves of cerebrospinal fluid that normally wash over brains during sleep can be made to pulse in the brains of people who are wide awake, a new study finds.
Previous research has suggested that the clear fluid may flush out harmful waste, such as the sticky proteins that accumulate in Alzheimer’s disease (SN: 7/21/18, p. 22). So being able to control the fluid flow in the brain might have implications for treating certain brain disorders. I think this [finding] will help with many neurological disorders,” says Jonathan Kipnis, a neuroscientist at Washington University in St. Louis who was not involved in the work. “Think of Formula One. You can have the best car and driver, but without a great maintenance crew, that driver will not win the race:’ Spinal fluid flow in the brain is a major part of that maintenance crew, Kipnis says. But he and other researchers, including the study’s authors, caution that any potential therapeutic applications are still far off.
I think this [finding] will help with many neurological disorders,” says Jonathan Kipnis, a neuroscientist at Washington University in St. Louis who was not involved in the work. “Think of Formula One. You can have the best car and driver, but without a great maintenance crew, that driver will not win the race:’ Spinal fluid flow in the brain is a major part of that maintenance crew, Kipnis says. But he and other researchers, including the study’s authors, caution that any potential therapeutic applications are still far off. In 2019, neuroscientist Laura Lewis of Boston University and colleagues reported that strong waves of cerebrospinal fluid wash through our brains while we slumber, suggesting that sleep may give the brain a deep clean (SN: 11/23/19, p.11). The slow neural oscillations that characterize deep, non-REM sleep occur in lockstep with the waves of spinal fluid, the team showed. These flows are far larger than the rhythmic influences that breathing and heartbeat have on spinal fluid.
As brain activity during sleep causes blood to flow through the brain, spinal fluid flows in behind the blood. Such fluid infusions clear out toxic proteins and maintain constant pressure in the skull, experiments in mice have shown.
In the new study, “the first question we wanted to answer is, can you manipulate [blood flow] enough to also drive [fluid] flow when someone’s awake?” says Stephanie Williams, a neuroscientist also at Boston University.
To stimulate blood flow in the brain, Williams, Lewis, and colleagues showed six healthy adults a flickering checkerboard pattern. A mix of techniques, including functional MRI and electrodes, confirmed that the intense stimulation affected blood flow in the brain and allowed the team to see the order of events.
Neural activity increased when the flashing pattern was turned on, followed by increased blood flow. Cerebrospinal fluid flow was suppressed while blood flow increased, and then surged into the brain as blood flow ebbed when the stimulation stopped, the team reports March 30 in NOS Biology. Longer stimulation produced larger spinal fluid flows, suggesting it was possible to maximize the response.
The effect of brain activity on spinal fluid flow is separate from the influences of heartbeat and breathing, the team found. The brain has a way to control its own fluid flow; Lewis says.
The team did not measure whether the waking flows cleared waste from the brain. However, previous studies in mice have found that certain audiovisual stimuli reduce levels of toxic proteins linked to Alzheimer’s and Parkinson’s. Testing of the technique in humans is underway.
“It’s a beautiful study, butt wouldn’t draw therapeutic conclusions from this; says neurologist Steven Goldman of the University of Rochester Medical Center in New York. The brain’s fluid flow system is optimally set up for cleaning during sleep. “It would be more effective to just ensure a good night’s sleep; Goldman says. “Any manipulations over and above that would be best employed during sleep; Lewis’ team acknowledges that the induced flows were smaller than those seen during sleep.
But the change in flow was still ‘pretty substantial; Lewis says. The technique could help scientists figure out how the process might be disrupted in diseases like Alzheimer’s, she says.
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