Harvard Medical School and Boston College researchers have found that taking music lessons can strengthen connections between the two hemispheres of the brain in children, but only if they practice diligently.

For the children who practiced at least 2.5 hours a week, a region of the corpus callosum that connects movement-planning regions on the two sides of the brain grew about 25% relative to the size of the brain.

With every child, the researchers found that the size increase in the corpus callosum predicted the improvement on a nonmusical test that required the children to tap out sequences on a computer keyboard.