Discuss the implications of the of the split-brain procedure (severing of the corpus callosum) for the understanding of the connections between the left and right hemisphere.
The first known split-brain surgical procedure performed on humans’ was in the early 1940’s by Van Wagenen and Herren, in which both intended to control seizures of patients who suffered intractable epilepsy (Francois Boller, Jordan Graffman, 2000). The procedure performed by Van Wagenen and Herren was based on the speculation as to the role of the corpus callosum in the spread of epilepsy. The patients of the early 1940’s who underwent the split-brain surgery often did not experience any relief of their epilepsy and therefore surgeons had stopped performing this unworkable procedure. It was not until twenty years later that a complete commissurotomy (severing of connections of the hemispheres) was performed on a former Paratrooper who was experiencing life threatening seizures. (Francois et al, 2000). The doctors who performed the surgery, Phillip Vogel and Joseph Bogen felt the corpus callosum was a critical pathway for the spread of epileptic discharge from one hemisphere to the other (Francois et al, 2000). This took place in 1962 and was done by Vogel and Bogen, who successfully separated the two cerebral hemispheres, which was effective in stopping the patient’s seizures. The same procedure was also subsequently performed on a series of patients who suffered intractable epilepsy. Research on split-brain had started with animals such as rats, cats and monkeys, which had led to the development of techniques to assess the function of each hemisphere (Francois et al, Myers 1956, Myers and Sperry 1958). This started 30 years of research on human beings, and in turn it effectively gave insights to the functions of the two hemispheres and the ways in which they interact with each other (Francois et al, Gazzaniga 1998). The early surgeries in the 1940’s involved invasion of the lateral and third ventricles of the brain in order to divide many of the forebrain commisures. Due to these early techniques performed by surgeons, it resulted in a high risk of infection as well as damage to the brains surrounding structures. This technique of surgery on patients frequently exhibited an ‘acute disconnection syndrome’ (Francois et al). Characterised by mutism, apathy, confusion, left limb apraxia and partial motor seizures (Francois et al, Bogen 1993, Wilson, Reeves and Gazzaniga 1982). Dividing just the corpus callosum and hippocamal commissure proved to be an effective way of controlling seizures. Employing this method significantly lowered the risk of infection and damage to the surrounding areas of the brain. The term split-brain is generally applied to both colostomy (corpus callosum) and commissrotomy (Francois et al). The corpus callosum has over 200 million axons passing through it, along with the anterior commissure. It provides the only direct link between the cortical from the left and right hemisphere. The two cerebral hemispheres are connected by the corpus callosum and is the brains largest collection of connective fibre. Because of the callosum each of the brains areas of the association cortex knows what is happening in corresponding to the other side of the brain. According to Wayne Weiten, 2008, the left hemisphere is more dominant than the right hemisphere, because the thoughts are usually coded in terms of language. It was also given the majority of credit for handling the higher mental processes, for example reasoning, problem solving, planning and remembering. The right hemisphere, according to Wayne Wandsworth was viewed as the non-dominant of the two hemispheres, which did not have any particular special abilities or functions. According to Martin et al, 2007 the left hemisphere takes part in analysing information and the right hemisphere is used for putting things together, which makes it good at ‘holistic’ activities. However, this...
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