By means of a prominent groove, called the longitudinal fissure, the brain is dividid into two halves called hemispheres. At the base of this fissure lies a thick bundle of nerve fibers, called the corpus callosum, which provides a communication link between the hemispheres. The left hemisphere controls the right half of the body, and vice-versa, because of a crossing of the nerve fibers in the medulla.

Although the right and left hemispheres seem to be a mirror image of one another, there are important functional distinctions. In most people, for example, the areas that control speech are located in the left hemisphere, while areas that govern spatial perceptions reside in the right hemisphere.

The central sulcus and the lateral sulcus, divide each cerebral hemisphere into four sections, called lobes (see Division of the Cortex Into Lobes). The central sulcus, also called fissure of Rolando, also separates the cortical motor area (which is anterior to the fissure).

Starting from the top of the hemisphere, the upper regions of the motor and sensory areas control the lower parts of the body.

Cerebral Dominance

This term refers to the fact that one of the cerebral hemispheres is "leading" the other one in certain functions. The difference is most realized in language and manual skills. Although there is an individual and cultural variability, language is mostly represented on the left hemisphere, while non-verbal skills tend to be represented on the right hemisphere.

Broca's area and Wernick's area refers to language function and lie on the left hemisphere.

Contd. The External Architecture of the Brain
By: Silvia Helena Cardoso, PhD
In: Brain & MInd