This is a diffusion spectrum MR image of human brain showing curvature of two-dimensional sheets of parallel neuronal fibers that cross each other at right angles. (Credit: Van Wedeen, M.D., Martinos Center for Biomedical Imaging, Massachusetts General Hospital)
"We found the brain is built from parallel and perpendicular fibers that cross each other in an orderly fashion. Finding this kind of simple organization in the forebrain of higher animals was completely unsuspected," says Van Wedeen, MD,
It is well known that neural pathways in the spinal cord and brain stem are organized in three principal directions -- head to tail, side to side, and front to back -- all of which are either parallel or perpendicular to each other and reflect the basic patterns of embryonic development.