cerebral hemisphere

n. One of the two halves of brain separated by the longitudinal or interhemispheric fissure. They are relatively symmetrical. In the convexity of the cerebral hemispheres four lobes are distinguished: frontal, parietal, temporal, and occipital. Two major landmarks are observed: the central (or Rolandic) fissure, separating the frontal and parietal lobes, and the lateral (or Sylvian), separating the temporal lobe from the parietal and the frontal. Parietal and occipital lobes are separated by the parietal-occipital sulcus; there is no evident landmark separating the temporal and occipital lobes. Sometimes, the insula (deep in the lateral fissure) is regarded as a fifth cortical lobe. Both cerebral hemispheres are interconnected mainly by the corpus callosum, as well as by some other smaller commissures: the anterior commissure, posterior commissure, and hippocampal commissure. The outer layer of the cerebral hemispheres corresponds to the cerebral cortex, composed of six layers of neurons (gray matter); internally, they are mainly composed of incoming and outgoing fibers from gray matter (white matter). Cerebral hemispheres are covered by three membranes known as meninges (the dura, arachnoid, and pia).

- AA

► See also CEREBRAL DOMINANCE and HEMISPHERIC SPECIALIZATION