During deep sleep, waterlike fluid moves through and around brain, helping remove metabolic waste associated with disorders including Alzheimer’s disease. This cleanup process is known as glymphatic system. It was first described in 2012 by Maiken Nedergaard, pioneering neuroscientist and co-director of University of Rochester Center for Translational Neuromedicine.
Although scientists have learned great deal about glymphatic system, major questions remain about how it actually works. One of biggest uncertainties is speed at which fluid travels through different parts of brain. Measuring such slow circulation in living brain is especially challenging because researchers need to observe it without causing permanent damage.
Challenge Of Measuring Brain Fluid Flow Slow Circulation
“You can put microscope on small patch of brain and watch what’s happening there with lot of detail, and we’ve worked with that type of data in past, but it’s only tiny view of overall process,” says Professor Douglas Kelley from URochester’s Department of Mechanical Engineering.
“If you want to image whole brains, MRI is great approach because it gives you three-dimensional view. But MRI has serious limitations too, biggest of which is that it does not capture fluid flow velocity, at least not for flows this slow,” Kelley explained.
To overcome limitation, Kelley and researchers from URochester, Brown University, and University of Copenhagen turned to artificial intelligence. New study, published in Science Advances, describes method that uses physics-informed artificial intelligence to extract fluid flow speeds from MRI data. Researchers trained neural networks using videos that showed dye spreading through brain tissue over time. From those changes, AI models could estimate both speed of fluid and permeability of surrounding brain tissue.
Analysis: Brain’s Cleanup System Has Two Dramatically Different Speeds
Results revealed two major pathways by which glymphatic system helps remove particles from brain, including amyloid beta proteins associated with Alzheimer’s disease. Researchers found these pathways operate at dramatically different speeds.
In more open areas around brain, including region between skull and brain’s surface, waterlike fluid travels at few microns per second. Deeper inside brain tissue, however, fluid moves far more slowly.
Flow rate inside dense tissue is roughly 50 times lower than in open spaces. This large difference gives researchers clearer picture of how waste may be transported through different brain environments.
Fluid can move relatively quickly through open spaces, while movement through dense brain tissue is much more gradual. Therefore, waste clearance is fast in outer channels and slow inside.
From Animal Brains To Human Health: Screening Alzheimer Early
For now, research team is working to establish baseline measurements of brain fluid flow in animals such as mice. Those measurements are helping researchers refine and improve AI tools. Eventually, they hope to compare glymphatic circulation in healthy and diseased brains, as well as in young and old brains. Major long-term goal is to extend technique to humans.
“We’re working hard toward being able to measure flow of waterlike fluids in and around human brains because then clinical applications get lot more important and exciting,” says Kelley. “We hope to someday be able to see whether Alzheimer’s patient has poor circulation in their brain or even screen for poor circulation earlier in life to try to stave off Alzheimer’s,” he said.
“Or we could check when somebody has been concussed to see whether fluid circulation in brain is disrupted. This study gets us step closer,” Kelley added.
If researchers can eventually measure these slow fluid movements reliably in people, technique could offer new way to investigate whether brain’s natural waste-clearing circulation changes with Alzheimer’s disease, aging, or traumatic brain injury. Good deep sleep may therefore be critical for allowing this two-speed cleaning system to work efficiently each night.
Q&A
Q: How does brain clean itself while you sleep?
A: During deep sleep, glymphatic system moves waterlike fluid through brain, removing metabolic waste like amyloid beta linked to Alzheimer’s.
Q: How fast does brain fluid flow during sleep?
A: AI study found fluid moves at few microns per second in open areas around brain, but 50 times slower deep inside dense brain tissue.
Q: Can poor brain cleaning cause Alzheimer’s?
A: Researchers hope new AI MRI method will eventually screen if Alzheimer’s patients have poor glymphatic circulation, potentially enabling earlier detection.
FAQ
1. What is glymphatic system?
Glymphatic system is brain’s waste-clearing network first described in 2012 by Maiken Nedergaard, using fluid to remove toxins during deep sleep.
2. Where was new brain cleaning study published?
Study published in Science Advances by researchers from University of Rochester, Brown University, and University of Copenhagen using physics-informed AI.
3. How did AI measure slow brain fluid flow?
Team trained neural networks on videos of dye spreading through brain tissue, allowing AI to estimate fluid speed and tissue permeability from MRI data.
4. Why is deep sleep important for brain health?
Deep sleep enables glymphatic fluid to circulate and clear Alzheimer’s-associated proteins; disrupted circulation may link to aging and brain injury.
5. Can this technique be used in humans yet?
Not yet; team is establishing baselines in mice, with long-term goal to measure waterlike fluid flow in human brains for clinical screening.
Disclaimer: This article is for informational purposes only and does not constitute medical advice.
