Split Brain

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Split-Brain Patients: The independent functioning of the left and right hemisphere when no longer connected by the corpus callosum.

The human brain is a dynamic and elastic processing unit that manages the great extent of human life. This entails both conscious and unconscious functioning of each human system. For example, the brain controls emotions through behaviors, physiological responses (both autonomic and hormonal), and feelings in response to stimuli from the environment (Carlson, 2011). The human brain is constructed of two major hemispheres, each linked to functional processing of opposite sides of the body. The two hemispheres are linked by a dense bundle of nerves referred to as the corpus callosum, or “hard-skinned body.” Though, the human brain should not be thought of as two dependent hemispheres connected by a bridge of dense neuronal fibers because even when the bridge is cut each hemisphere is able to perform independent of the other. Each hemisphere has its own distinct characteristics and specialized abilities, as demonstrated by split-brain patients who have had their corpus callosum severed, in most cases to alleviate extreme epilepsy (Bainbridge, 2008). Split-brain patients show surprising responses to experiments designed to isolate each hemisphere to process information on its own; such experiments have uncovered that while the human brain has specialized interworking parts, the left hemisphere is the literal, talkative side while the right hemisphere interprets information in a more relational manner and is unable to verbalize. Maurice Ravel, a famous composer, suffered a stroke in 1933. As a result of his stroke, Ravel found himself unable to compose music. Worse, Ravel’s ability to enjoy music was in no way compensated and he could still dream up his music ideas, but was unable to transfer any idea from thought to paper. Ravel could no longer write or perform his musical genius. Neurologists believe Ravel’s stroke disabled the left hemisphere of his brain where musical sound is translated and broken down into symbolic parts. The right hemisphere is utilized to enjoy music, but the left is needed to work out notes and instrumental movements. Maurice Ravel was also severely handicapped in his ability to manipulate written language, taking a recorded eight days to write a fifty word letter (Johnson 158-9). The right and left hemispheres play different roles in processing information; when separated the two halves can work separately to make whole understandings of processed stimuli, but if damaged a specialized unit of the brain cannot be easily replaced. Patients who undergo split-brain surgery do not have any noticeable ill effects: personality, memory, or ability to live daily life does not change. Split-brain patients were tested by Gazzaniga and Smylie for facial recognition by asking patients to identify a face on a board of 10 photos after an image had been flashed to either the left or right visual field for 120msec; the research indicated only that the left hemisphere has slight advantage over the right in remembering faces in this way (Bruyer, 1986). R. Sperry conducted research on cats with split brain and found that there is no difference in the ability for the cat to learn with either hemisphere. In R. Sperry’s experiments the brains of cats were surgically manipulated so the connection between hemispheres and the optic nerves were severed so only one hemisphere received data from one eye. The cats were blindfolded on one eye and taught to run a maze to find food. When the blindfold was reversed so the cat could only see out of the opposite eye, the cat was unable to identify its path to food and had to relearn the entire maze (Gazzaniga 1967). In an experiment conducted on split brain patients by D. Zaidel, pictures of faces were distorted by moving facial structures such as the nose or mouth to places were they did not belong. For example, the mouth would be...
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