Latin for “tough body,” this mass of more than 200 million nerve fibers helps connect the left and right hemispheres of the cerebrum, our brain’s largest and uppermost section. This connection allows the two hemispheres to communicate more efficiently. And while there’s been much debate over whether or not women have bigger corpora callosa, there’s evidence that musicians may have the edge: Researchers have found that starting musical training before the age of 7 can boost connectivity in this brain area.