On a basic level, the brain consists of regions of gray matter that are interconnected by white matter. Composed primarily of neuronal cell bodies, gray matter is the center of activity, from higher learning and memory to sensory reception and muscular responses. White matter consists mainly of myelinated axons, the part of neurons that relay signals to and from gray matter regions. “This research shows that you don’t ramp up the output of your gray matter regions as well when you’re older. “More and more, research shows us that the structure of the brain affects its function, especially in terms of aging and white matter.