Artificial intelligence reveals hidden fluid flow patterns in sleeping brains

When a person goes into deep sleep, waterlike fluid circulates around the brain, washing away metabolic waste that is linked to diseases such as Alzheimer's. This process, known as the glymphatic system, was first described in 2012 by Maiken Nedergaard-a pioneering neuroscientist and co-director of the University of Rochester Center for Translational Neuromedicine.

But questions remain about the system's mechanics-notably, how quickly the fluid circulates around the brain. Studying the circulation within a living brain is difficult to do without causing irreparable harm to a subject.

You can put a microscope on a small patch of the brain and watch what's happening there with a lot of detail, and we've worked with that type of data in the past, but it's only a tiny view of the overall process. If you want to image whole brains, an MRI is a great approach because it gives you a three-dimensional view. But an MRI has serious limitations too, the biggest of which is that it does not capture the fluid flow velocity, at least not for flows this slow."

Kelley and his colleagues from URochester, Brown University, and the University of Copenhagen turned to artificial intelligence for help. In a new study published in Science Advances, they outline how they used physics-informed artificial intelligence to determine fluid flow velocities from magnetic resonance imaging (MRI) data. Using videos of dye spreading across brain tissue over time, the neural networks the researchers built were able to deduce how fast the fluid flows and how permeable the brain tissue is.