The human brain contains about 100 billion interconnecting neurons, or cells that create and transmit messages. Scientists are just beginning to understand how this extremely complicated organ is "wired" to process information and relay commands to the body. Using a cutting-edge brain imaging technique called diffusion spectrum imaging, a team of Swiss and American researchers has produced the first detailed map of nerve fibers in the human cerebral cortex, the outer layer of the brain that is believed to be responsible for our species' unique mental capacity.