Understanding how the brain functions, particularly how information is processed during different activities, is difficult without knowing how many axons are in the brain and how many connect different functional regions. An approach by Burke Rosen and Eric Halgren at the University of California, San Diego, U.S. published March 24 in the open-access journal PLOS Biology, shows that despite the functional importance of connections between far-reaching regions of the brain, the actual number of these connections is low.