Supercomputing reveals mechanisms behind brain's waste handling
Our simulations show that amyloid beta, the substance underlying plaque aggregates that eventually is killing brain cells in Alzheimer's disease, should be able to diffuse out to the blood vessels. This is in contrast to a recent popular theory that the brain fluid flows like rivers through the tiny clefts around the brain cells, bringing the waste products along. It is, however, not possible to measure the pressure differences within these tiny clefts. We solved this by using electron microscopy images of the clefts and then simulating the flow through these clefts. This required huge simulations, solving 100 million differential equations, and to our surprise we found that brain fluid will not be able to flow like rivers thorough the extracellular volumes. The cleft are too narrow. However, simulations revealed that amyloid and other waste products is transported out of these clefts by diffusion, the same mechanism bringing molecules of smell into your nose in a room....