Scientists combined MRI with physics-informed artificial intelligence to measure the slow waterlike flows that help clear metabolic waste from the brain. The glymphatic system was first described in 2012 by Maiken Nedergaard at the University of Rochester; it has been linked to conditions such as Alzheimer’s disease. Professor Douglas Kelley, from the University of Rochester’s mechanical engineering department, says MRI cannot capture velocities this slow in living brains, so the team turned to AI.
In a study published in Science Advances, researchers trained neural networks on videos that show dye spreading through brain tissue. The AI estimated both fluid velocity and tissue permeability from those videos. The results identify two main clearance routes: a faster flow that moves at a few microns per second around open regions (for example the surface between skull and brain) and a much slower trickle through deep tissue at about fifty times lower speed. These pathways help remove particles such as amyloid beta proteins linked to Alzheimer’s.
So far the team has gathered baseline data in animals such as mice and hopes to compare fluid flow in healthy and sick brains and in young and old subjects. Kelley says measuring human brain circulation would make the clinical applications more important, for example checking circulation in Alzheimer’s patients, screening earlier in life, or assessing fluid disruption after a concussion. Additional collaborators are from Brown University, URochester, and University of Copenhagen. The research was supported by the NIH National Center for Complementary and Integrative Health and the NIH BRAIN Initiative.
Difficult words
- glymphatic system — Brain pathways that remove fluid and waste.
- permeability — How easily fluid moves through tissue.
- neural network — Computer model that learns from example data.neural networks
- clearance — Removal of unwanted material or fluid.
- amyloid beta protein — Protein that can form plaques in brain.amyloid beta proteins
- baseline — Initial data used for comparison later.
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Discussion questions
- How could measuring brain fluid circulation in humans help diagnose or treat Alzheimer’s?
- What challenges might researchers face when comparing fluid flow in young versus old or healthy versus sick brains?
- Do you think AI trained on dye videos from animals will give accurate results for human brains? Why or why not?
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