Since that time, a number of discoveries have been made about the specific parts in the brain that are related to language functions. We now know that the most important parts are in areas above the left ear. In order to describe them in greater detail, we need to look more closely at some of the gray matter. So, take a head, remove hair, scalp, skull, then disconnect the brain stem (connecting the brain to the spinal cord) and cut the corpus callosum (connecting the two hemispheres). If we disregard a certain amount of other material, we will basically be left with two parts, the left hemisphere and the right hemisphere. If we put the right hemisphere aside for now, and place the left hemisphere down so that we have a side view, we’ll be looking at something close to the accompanying illustration (adapted from Geschwind, 1991).

The shaded areas in this illustration indicate the general locations of those language functions involved in speaking and listening. We have come to know that these areas exist largely through the examination, in autopsies, of the brains of people who, in life, were known to have specific language disabilities. That is, we have tried to determine where language abilities for normal users must be by finding areas with specific damage in the brains of people who had identifiable language disabilities.