Lateralization of Function in Cerebral Hemispheres

Lateralization of Function in Cerebral Hemispheres

One of the major goals of neuroscience is to be able to understand the relationships between the structures of the nervous system and a persons outward behavior. Often times it is difficult or unethical to directly study the nervous system during a behavior and indirect methods must be used instead. One example of such an indirect method is using a subjects preferred hand to predict which of the two Cerebral Hemispheres is dominant. The are some difficulties with his method of studying lateraliztion of function but if it can be better understood it could have many practical and theoretical implications for the study of neuroscience.

The Cerebral Hemispheres are very similar in appearance, but they differ significantly in their structure. One of the best known differences between the two structures is motor control; the right hemisphere controls the left half of the body and the left hemisphere controls the right half of the body. These motor control differences were discovered mainly through the examination of paralysis caused by stokes or other damage to a specific hemisphere.

In 1861 the theory of lateralization of function was expanded with the discovery by Paul Broca of structure in the right hemisphere that controlled speech, this structure is now known as Broca's area Like many other advances in neuroscience this discovery was made possible by an unfortunate stroke victim, who in this case lost his ability to speak. After his death Broca examined his brain and discovered damage in the right hemisphere at this now famous location. This finding was followed soon after by the discovery of an area, also in the right hemisphere, responsible for understanding of written word. This area become know as Wernicke's area named after the man who discovered it by "studying patients with select comprehension deficits" (1) and comparing these deficits with damages to the brain.

These two discoveries created a watershed of experimentation as other scientists attempted to discover more functional differences between the hemispheres. This body of research has created a very stereotyped understanding of the two hemispheres. The left hemisphere is known as the language hemisphere. It is also believed to control general cognitive functions. Some researchers have gone so far as to ascribe consciousness to the left hemisphere. The right hemisphere is assigned nonverbal process such as special relations and the detection of complicated auditory tones .