Cerebral Lateralization and Functionality

Cerebral lateralization research has four methods that help gain a better understanding of brain function. One method is the sodium amytal test. In this test, researchers are able to access language abilities before neurosurgery. With this test, the procedure is to inject sodium amytal into a patient’s carotid artery in the neck. The injection anesthetizes the side of the hemisphere that is injected and allows the other hemisphere’s capacities to be assessed for language abilities.

  A second method of cerebral lateralization is dichotic listening. During a dichotic listening test, “three pairs of spoken digits are presented through ear phones: the digits of each par are presented simultaneously, one to each ear.” (Pinel, 2009) An example of this would be a person who is taking the test might hear four, zero, eight in one ear and at the same time can hear five, three, and six in the other. This testing shows that most individuals show left-hemisphere dominance because a person’s right ear will register more.

Functional brain imaging is a third method, and involves a subject engaging in an activity, say for example reading. During this activity the brain is monitored by positron emission tomography. In this test, the left hemisphere of the subject’s brain shows more activity then the right.

Early research in cerebral lateralization was through experimenting with lesions in both the left and right hemispheres of the brain. Researchers would study the effects of lesions which helped to determine certain functionalities of the left hemisphere and the right. Discoveries of left hemisphere damage and the effect on functions of the brain led to a belief that the left hemisphere is dominant over the right. This method is known as the unilateral brain lesions test.



  Pinel, J. P. J. (2009). Biopsychology. Boston, MA: Pearson.