The Split Brain In Man Essay, Research Paper
The Split Brain in Man
The effects of a split-brain operation are most dramatic when sensory information is limited to a single hemisphere because when the corpus callosum is cut, the brain is divided into two separate hemispheres, the right and the left. R.Sperry and M.Gazzaniga show the dramatic effects in various experiments conducted. In one such experiment, lights were flashed on the left visual field of a split-brain person; the person reported that they had not seen any lights. This is due to the right hemisphere’s disconnection with the speech centers of the brain, which is located in the left hemisphere. However, the patient could point to the direction where the lights were flashed as pointing does not involve the speech portion of the brain. Another example that shows the dramatic way sensory information is interpreted by a single hemisphere is when the word heart was flashed having the he to the left and the art to the right. When the patient was asked what they had seen flashed on the screen they would answer art as the left hemisphere is responsible for speech. However when asked to point to a card having the word art or he on it the patient would point with their right hand to he therefore showing that when the right hemisphere could express itself it would. From the examples above it is clearly seen that with split-brain patients when doing normal tasks using both sides they can continue fine but when the tasks are specific to one side of the brain they lack the information needed from both sides.
The effects of sectioning the optic chiasm causes the information from the left eye to be dispatched to the left-brain and the information from the right eye only being dispatched to the right brain. When the optic chiasm is cut, an animal could respond normally and learn to perform a task, when that eye was covered the animal would have no recognition to the same problem and would have to learn it over again. (Gazzaniga, The Split Brain in Man). An example of this in patients with split-brain is when they are tested visually. In the test where the word heart was flashed having he on the on the left and art on the right the patient could say they saw the word art as speech is on the left hemisphere. When asked to point to what they had seen the patient would point to the word he showing that the information is being sent to the right hemisphere but can not be expressed verbally. This experiment shows the effect of sectioning the optic chiasm in humans and the effect it plays on visual interpretations.
The ipsilateral motor control can be determined using a split-brain subject by giving an object in the person s right hand, from which sensory information is sent to the left hemisphere, and the patient is able to name and describe the object. When held in the left hand the patient could not describe the object verbally but was able to identify it in a non-verbal test such as matching it in a collection of things. Tests of ipsilateral motor control in these split-brain patients revealed that the left hemisphere of the brain exercised normal control over the right hand but had less than full control of the left hand. Similarly, the right hemisphere does the opposite. When the two hemispheres were in conflict, the hemisphere on the side opposite the hand took control and overruled the side of the brain with weaker control. Each hemisphere not only received input from the opposite side but also from the same side.
The phenomenon of unilateral emotions is that in certain mental processes the left and right hemispheres were almost identical. In tests done by Roger Sperry and Michael Gazzaniga unilateral emotions were observed. One test was presenting the split-brain patients with ordinary images and then suddenly a picture of a nude woman an amused reaction was seen on both sides of the hemispheres when tested independently. When presented to the left hemisphere the female patient laughed and identified what she had seen as the left hemisphere contains speech. On the other hand, when the nude picture of the woman was presented to the right hemisphere the patient said she did not see anything but then immediately after a sly smile spread over here face and she began to chuckle. The two hemispheres both showed an emotional response and this showed that in a spilt-brain situation they were really dealing with two brains able to have separate emotions.