A topic covered in lecture and also in the Lilienfeld text this past week was the Split brain subject test. This test is performed on someone who has had a procedure done to their corpus callosum in which the fibers connecting the two hemispheres of the brain are split. This procedure typically offers relief from epileptic seizures. The studies done on these individuals offer an interesting insight into how the human brain works. Basically, the left side of our brain is responsible in forming the words around what we are seeing. This is validated in a test performed, where a subject with a split-brain is instructed to focus on a dot in the center of a projection screen. Then for a split-second an image is flashed onto both sides of the screen. The subject is then instructed to choose from a group of cards what best represented the image they saw. In the test that was demonstrated in class, an image of a snowy scene was flashed on the left side of the screen while a picture of a chicken was flashed on the right. When the subject was instructed to select a card from the group it selected a shovel while saying the word "chicken". Although the subject was unaware of why they made this choice, they still tried to rationalize their choice by saying that you need a shovel to clean out a chicken coop. This test confirms that the left side of the brain is used for speech because it was the subjects left hemisphere that would process the image of the chicken on the right side of the screen.
Source: Lilienfeld text, Lecture