Cerebral Lateralization

There are four methods of studying cerebral lateralization and the functions of the right and left hemispheres of the brain. Three of these are: the sodium amytal test, dichotic listening, and functional brain imaging. The relationship between left and right handedness and language has also long been considered a method of cerebral lateralization.

When the sodium amytal test is given, a neurosurgeon injects the chemical into the carotid artery on one side of the neck anesthetizing that side of the brain for a few minutes and allowing the other side to be tested for language functionality. The process is then repeated for the other side. Since the left hemisphere controls language function, the subject may temporarily lose speech when that side is anesthetized. Generally the right hemisphere makes more mistakes on presented flash cards than the left. (Pinel, 2007)

When the dichotic listening test is given, "three pairs of spoken digits are presented through earphones; the digits of each pair are presented simultaneously, one to each ear" (Pinel, 2007, p. 445). The subject is then asked to repeat back the digits heard. As a rule, memories of digits spoken into the right ear are stronger as it is the left hemisphere that is dominant for language though, of course, this is not always the case. For example; if 4, 7, 2 was given in the right ear and 9, 1, 3 simultaneously into the left, the subject should have a greater likelihood of remembering 4, 7, 2.

During the Functional Brain Imaging test the subject engages in some activity such as speaking or reading and brain activity in each hemisphere is monitored using either MRI (Magnetic Resonance imaging) equipment or PET (Positron Emission Tomography). If the subject is reading brain activity in the left hemisphere should be higher. (Pinel, 2007, p. 445)

Left and right handedness has a connection with cerebral lateralization and language. It has been determined that the "the left hemisphere is dominant for...