The hemisphere of the brain that specializes in spoken and written language, logic, number skills, and scientific concepts.

The left-brain hemisphere neurologically controls the right side of the body and is connected to the right-brain hemisphere by an extensive bundle of over a million nerve fibers called the corpus callosum. Scientific study of the brain hemispheres dates back to the 1800s. In the 1860s, French physician Paul Broca (1824-1880) observed speech dysfunction in patients with lesions on the left frontal lobes of their brains. Initially, the discovery of specialized functioning of the right and left sides of the brain led to the assumption that all higher...