Researchers at the USC Mark and Mary Stevens Neuroimaging and Informatics Institute have assembled diffusion MRI scans from 54,583 people across 19 international datasets to map how the brain's white matter - the wiring that lets separate brain regions talk to each other - develops, matures and declines with age. The work, published in Nature Communications, produces what amounts to a set of growth charts for neural pathways, one of the largest reference models of its kind built for the human brain.
The comparison to pediatric growth charts is the researchers' own. "Just as pediatric growth charts help clinicians determine whether a child's height or weight is developing as expected, these brain charts provide a reference for how the brain's neural pathways typically change over the lifespan," said Julio E. Villalon-Reina, MD, PhD, the postdoctoral researcher who is the study's first author. The point of a reference curve is comparison: it lets researchers see when an individual's brain wiring sits outside the expected range for their age.
Diffusion MRI works by tracking how water moves through brain tissue. Because that movement is constrained by microscopic structures such as nerve fibers and the myelin sheaths that insulate them, the method picks up changes in tissue organization that a standard structural scan would miss. Until now, interpreting those measurements has been difficult without a large-scale sense of what normal looks like at a given age.
For dementia research, the practical value lies in detection. The team says the charts give investigators a new way to spot subtle patterns tied to aging, Alzheimer's disease, schizophrenia risk and other neurological and psychiatric conditions - deviations that might otherwise be dismissed as normal variation. This is a research tool rather than a clinical test, but reference models of this scale are the sort of infrastructure that makes it possible to ask whether white matter changes show up before symptoms do.