Surgical Severing of the Corpus Callosum - Essay Example

? Study of individuals Study of individuals The surgical severing of the corpus callosum, commonly referred to as the split-brain operation, was initiated during the 1940’s as a means of treating severe cases of epilepsy. At the same time, it was adopted for patients where medication could not manage the condition. The corpus collosum is a special structure that links the left and right hemispheres of the brain, and thus, provides a means through which the two hemispheres can communicate with each other. Lateralisation of the function is a term that is applied to mean the process of allocation of tasks and skills between the two hemispheres (Sperry 1966, p.18). For many decades, the concept of lateralisation of function has been subject to numerous studies and controversies. Gall and Spurzheim came up with the first theory in 1824 when they sought to explain that personality characteristics could be identified by examining the shape of an individual’s skull. Although it was the first theory postulating that different sections of the brain was responsible for different functions, it was disapproved after other theories pointed out that various sections of the human brain were responsible for causing different human behaviours. Major developments in comprehension of lateralisation function came during the 1860’s after Paul Broca, a French physiologist carried out an in-depth examination of the brain of a deceased patient. Modern research of split-brain operation was pioneered during the 1950’s, by Roger Sperry and Michael Gazzaniga. The two researchers worked on each hemisphere so that they could independently examine the specific functions of the sections. The results of their research revealed that there was a particular trend among patients. In addition, interhemispheric transfers of gnostic, sensory, motor, and perceptual tend to be blocked in a dramatic way (Sperry 1966, p.54). The research enabled Sperry and Gazzaniga to gain insights into differences between the two hemispheres and the mechanisms through which they interact. Roger Sperry performed one notable experiment in a bid to comprehend the specific functions of each hemispheres and the nature of communication taking place between the two. The experiment, involved patients being instructed to stare at a point on the centre of a screen, then stimulus was projected on one section of the screen. With the help of the projection, Sperry was able to trace the stimulus to only one hemisphere of the brain, and ultimately examine the function of the corpus collosum in enabling communication to take place between the two hemispheres. He was able to study the role played by the corpus collosum by observing the response of the hemispheres to stimulus without the presence of corpus collosum. The split-brain operation was made possible by the discovery that commissural fibres join hemispheres of the human brain together that aids internal communication. Surgeons discovered that epileptic seizures resulted from millions of brain cells being engaged in excessive firing. People who experience major epileptic seizures can exhibit uncontrollable movements, and finally lose consciousness. Most of the seizures involved both hemispheres, and thus, surgeons noted that if the two hemispheres could be separated, then seizures could be controlled in one half of the brain. Consequently, it would reduce damage caused to the patient. However, in most cases, surgical operation is applied as a last resort if medication fails to contain the impact of epilepsy (Sperry 1966, p.125). Roger Sperry was able to realize a prospect through examination of patients with hemisphere disconnection. In his experiment, he strictly used patients whose cerebral hemispheres had been disconnected since they all had histories of advanced epilepsy. From his examination, there are many insights that could be gained from functionality of the two hemispheres and the manner in which information is exchanged. When patients with disconnected cerebral hemispheres were presented with an image from the left visual field, the patients were unable to vocally name what was observed. The most accurate explanation for such occurrence is that, in most people, speech-control centre is situated on the left side of the brain. Additionally, images viewed from the left visual field are normally transferred to the right side of the brain. Cerebral disconnection inhibits communication between the two hemispheres, and thus, patients could not name an image that was observed from the left visual field. It was also noted that individuals who had their speech control centres located on their right hemispheres exhibited the same symptoms when shown an image from the right visual field. Through Sperry’s experiments, it was also noted that a patient using the left visual field could pick an object with the left hand and perfectly recognize it. This was attributed to the fact that the left hand was controlled by the right side of the brain, and thus, they could be able to name the object. Roger Sperry explained that everything that was observed pointed out that cerebral disconnection left patients with two separate minds, or rather, two separate spheres of consciousness. The observations indicated that what takes place within the right hemisphere was completely separate from the realm of awareness of the left side. The mental division were mainly demonstrated concerning memory, learning, volition, cognition, and perception (Sperry 1966, p. 299). In normal cases, both tactile and visual information from the left visual field are communicated to the right hemisphere, which is responsible for controlling the extremities experienced in the left side. Alternatively, tactile and visual information received from the right visual field are communicated to the left hemisphere, which is also responsible for containing extremities experienced by the right hemisphere. Auditory information acquired by the left or right ear is predominantly communicated to the opposite hemispheres of the brain. This implies that when patients with disconnected cerebral hemispheres are stimulated on the right section of the body, the left side of the brain will not know. Normally, the left hemisphere is responsible for controlling the understanding and articulation of non-emotional language. That is the main reason why split-brain patients are unable to recognize objects presented to their left hand. Split-brain patients are also unable to report the presence of stationary or moving images in the left side of their visual fields. When left hemisphere is disconnected, it cannot verbally describe auditory, images, and odour stimuli that is dichotically or tachistoscopically presented to the light cerebrum. When left on its own, the left hemisphere has trouble in identifying, naming, or recognizing environmental and emotional sounds. Such functionalities are often associated with the right hemisphere. Unlike the left hemisphere, a disconnected right hemisphere is able to indicate when some aspects tactfully or visually presented to the left side. Although disconnected cerebral hemispheres are unable to share information directly, they can independently produce and support mental activity. The right hemisphere mostly concerns itself with a second form of awareness, which dramatically varies from the mental system applied in the left hemisphere. However, it closely accompanies what seems to be central temporal sequence, which is a form of language that is dependent on the flow of consciousness within the left cerebrum. As demonstrated by Sperry, a disconnected right hemisphere, just like the left cerebral hemisphere, is capable of self-awareness, and thus, can plan the future, set goals and aspirations, exhibit social and political awareness, and show likes and dislikes. By so doing, the cerebral hemisphere can knowingly initiate behaviour, direct emotional reactions and response choices, recall and act upon specific desires, and impulses environmental events independently without the aid of the other cerebral hemisphere. Essentially, the brain of a normal person and that of split-brain individuals sustains the neuroanatomy for the sole purpose of supporting the existence of two psychic realms. What remains surprising is that there are no instances of a considerable degree of conflict arising during everyday activities. In most cases that were observed in the experiments, the disconnected right cerebral side demonstrated willingness to assist the left disconnected cerebral side in myriad activities. Such instances do not occur for the reason that both spheres, when joined, experience similar interests and goals. Normal experiences appeared to present a very different argument, even in cases involving normal individuals, since psychic functioning is normally plagued by conflict (Sperry 1966, p.302). A research that was conducted to study the impact of split-brain operation on children revealed that they experienced considerable difficulties in undertaking tasks, which required transfer of visual and tactile information between the two hemispheres. At the age below four years, language is normally lateralised to the left side of the brain. Therefore, when the two hemispheres are disconnected, verbal descriptions are often erroneous, impoverished, and incomplete. Reference Sperry, R., 1966, Hemisphere deconnection and unity in consciousness, McGraw-Hill, New York. Read More