cerebral hemisphere [L, cerebrum + Gk, hemi, half, sphaira, ball] , one of the halves of the cerebrum. The two cerebral hemispheres are divided by a deep longitudinal fissure and are connected medially at the bottom of the fissure by the corpus callosum. Prominent grooves, subdividing each hemisphere into four major lobes, are the central sulcus, the lateral fissure, and the parietooccipital fissure. Each hemisphere also has a fifth major lobe deep in the brain. The hemispheres consist of an external gray layer and an internal white matter that surrounds islands of gray matter called nuclei (the basal ganglia).
