Can Someone Live After Having Their Corpus Callosum Cut

Editor's note: Sarah Walls created the above image for this article. You lot can find the total image and all relevant information here.

In the 1950s and 1960s, Roger Sperry performed experiments on cats, monkeys, and humans to study functional differences between the two hemispheres of the brain in the United States. To do and then he studied the corpus callosum, which is a large bundle of neurons that connects the ii hemispheres of the brain. Sperry severed the corpus callosum in cats and monkeys to study the function of each side of the brain. He plant that if hemispheres were not connected, they functioned independently of one another, which he called a split-brain. The split up-brain enabled animals to memorize double the information. Later, Sperry tested the same idea in humans with their corpus callosum severed every bit handling for epilepsy, a seizure disorder. He found that the hemispheres in human brains had different functions. The left hemisphere interpreted language merely non the right. Sperry shared the Nobel Prize in Physiology or Medicine in 1981for his carve up-brain research.

Sperry also studied other aspects of encephalon function and connections in mammals and humans, across divide-brains, in 1940s and 1950s. In 1963, he developed the chemoaffinity hypothesis, which held that the axons, the long cobweb-like procedure of encephalon cells, continued to their target organs with special chemic markers. This explained how complex nervous systems could develop from a gear up of private fretfulness. Sperry and then as well studied brain patterns in frogs, cats, monkeys, and human volunteers. Sperry performed much of his inquiry on the split-encephalon at California Constitute of Technology, or Caltech, in Pasadena, California, where he moved in 1954.

Sperry began his research on carve up-encephalon in belatedly 1950s to determine the function of the corpus callosum. He noted that humans with a severed corpus callosum did not bear witness whatever significant difference in office from humans with intact corpus callosum, even though their hemispheres could non communicate due to the severing of the corpus callosum. Sperry postulated that there should be major consequences from cutting the brain construction, as the corpus callosum continued the two hemispheres of the encephalon, was large, and must have an important function. Sperry began designing experiments to document the effects of a severed corpus callosum. At the time, he knew that each hemisphere of the brain is responsible for movement and vision on the opposite side of the body, and so the right hemisphere was responsible for the left eye and vice versa. Therefore, Sperry designed experiments in which he could carefully monitor what each middle saw and therefore what information is was going to each hemisphere.

Sperry experimented with cats, monkeys, and humans. His experiments started with divide-brain cats. He airtight one of their eyes and presented them with ii different blocks, one of which had food under it. After that, he switched the eye patch to the other eye of the cat and put the food under the other block. The cat memorized those events separately and could non distinguish betwixt the blocks with both eyes open. Next, Sperry performed a similar experiment in monkeys, only made them use both optics at the aforementioned time, which was possible due to special projectors and calorie-free filters. The split-brain monkeys memorized two mutually sectional scenarios in the same time a normal monkey memorized i. Sperry concluded that with a severed corpus callosum, the hemispheres cannot communicate and each ane acts as the merely brain.

Sperry moved on to man volunteers who had a severed corpus callosum. He showed a word to 1 of the eyes and found that split-brain people could only remember the discussion they saw with their right heart. Next, Sperry showed the participants two different objects, ane to their left center but and one to their right eye only and then asked them to draw what they saw. All participants drew what they saw with their left eye and described what they saw with their right heart. Sperry concluded that the left hemisphere of the brain could recognize and clarify speech, while the right hemisphere could not.

In the 1960s when Sperry conducted his split-brain research on humans, multiple scientists were studying brain lateralization, the idea that one hemisphere of the brain is better at performing some functions than the other hemisphere. However, researchers did not know which tasks each side of the brain was responsible for, or if each hemisphere acted independently from the other.

Sperry describes his inquiry in cats in the article "Cerebral Organisation and Behavior" published in 1961. To test how the cut of the corpus callosum affected mammals, Sperry cut the corpus callosum of multiple cats and had them perform some tasks that involved their vision and response to a visual stimulus. After severing each cat´s corpus callosum, he covered one of the true cat´s eyes to monitor with which heart the true cat could see. Sperry could switch the heart patch from one eye to the other, depending on which visual field he wanted the true cat to use. Next, Sperry showed the cats two wooden blocks with different designs, a cross and a circle. Sperry put food for the cat under one of the blocks. He taught the cats that when they saw the blocks with 1 eye, for instance, the correct heart, the food was under the circle block, simply when they saw it with the left eye, the nutrient was under the cake with a cross. Sperry taught the cats to differentiate between those two objects with their paws, pushing the correct wooden block away to become the nutrient.

When Sperry removed the heart patch and the cats could see with both eyes, he performed the same experiment. When the cats could utilize both optics, they hesitated then chose both blocks almost equally. The correct eye connects to the left hemisphere and the left eye connects to the right hemispheres. Sperry suspected that since he cutting the corpus callosum in those cats, the hemispheres could not communicate. If the hemispheres could not communicate and the information from one centre only went to i hemisphere, then only that hemisphere would remember which block usually had nutrient nether it. From that, Sperry concluded that the cats remembered two different scenarios with two different hemispheres. He suspected that the cats technically had two unlike brains, equally their hemispheres could non interact and acted as if the other one did not exist.

Sperry performed a similar experiment with monkeys, in which he likewise cut their corpus callosum. He wanted to exam if both hemispheres could operate at the same fourth dimension, even though they were not connected. That required separation of visual fields, or making sure that the right middle saw a circle, while the left eye saw a cross, like in the cat experiment, but without an eye patch and both eyes would see something at the aforementioned time instead of interchanging between the open eyes. Sperry solved that by using two projectors that were positioned side-by-side at an angle and showed mutually exclusive images. For example, the projector on the correct showed a circumvolve on the left and a cross on the right, while the projector on the left showed a cantankerous on the left and a circle on the right. Sperry placed special light filters in front of each of the monkey´s eyes. The lite filters fabricated information technology then that each eye saw the images from but one of the projectors. That meant one of the eyes saw the circle on the correct and the cantankerous on the left, while the other heart saw the cross on the right and the circle on the left. From his experiments with cats, Sperry knew that there was no sharing of information from right and the left hemispheres, and then he made the monkeys memorize two different scenarios at the same time.

The left heart saw a scenario where nutrient would be dispersed when the monkey pressed the push corresponding to a cantankerous, while the correct eye saw a scenario where nutrient would exist dispersed when the monkey pressed a button corresponding to a circumvolve. Ultimately, it was the aforementioned push, but the eyes saw it differently because of 2 projectors and special calorie-free filters. Sperry concluded that both hemispheres of the brain were learning ii dissimilar, reversed, issues at the same time. He noted that the split-brain monkeys learned two issues in the time that it would take a normal monkey to learn one, which supported the assumption that the hemispheres were not communicating and each one was acting as the only brain. That seemed as a benefit of cut corpus callosum, and Sperry questioned whether there were drawbacks to the procedure.

Sperry performed the next set of experiments on human volunteers, who had their corpus callosum severed previously due to outside factors, such as epilepsy. Sperry asked volunteers to perform multiple tests. From his previous experiments with cats and monkeys, Sperry knew that one, the opposite, hemisphere of the brain would only clarify information from one center and the hemispheres would not exist able to communicate to each other what they saw. He asked the participants to look at a white screen with a black dot in the centre. The blackness dot was the dividing point for the fields of view for a person, and so the correct hemisphere of the brain analyzed everything to the left of the dot and the left hemisphere of the encephalon analyzed everything that appeared to the correct of the dot. Next, Sperry showed the participants a discussion on ane side of the black dot for less than a 2nd and asked them to tell him what they saw. When the participants saw the word with their right center, the left hemisphere of the encephalon analyzed it and they were able to say what they saw. However, if the participants saw the word with their left eye, processed past right hemisphere, they could not remember what the give-and-take was. Sperry concluded that the left hemisphere could recognize and articulate linguistic communication, while the right one could not.

Sperry so tested the function of the right hemisphere. He asked the participants of the same experiment that could not remember the discussion because it was in the left visual field to close their eyes and depict the object with their left hand, operated by the correct hemisphere, to which he presented the word. Most people could draw the picture of the word they saw and recognize it. Sperry besides noted that if he showed the word to the same visual field twice, then the person would recognize it equally a discussion they saw, but if he showed it to the different visual fields, then the participants would not know that they saw the give-and-take earlier. Sperry ended that the left hemisphere was responsible not only for articulating language, but also for understanding and remembering information technology, while the right hemisphere could only recognize words, simply was not able to articulate them. That supported the previously known idea that the language center was in the left hemisphere.

Sperry performed another similar experiment in humans to farther written report the ability of the right hemisphere to recognize words. During that experiment, Sperry asked volunteers to place their left mitt into a box with unlike tools that they could not see. After that, the participants saw a discussion that described one of the objects in the box in their left field of view only. Sperry noted that nearly participants then picked upwardly the needed object from the box without seeing it, just if Sperry asked them for the proper noun of the object, they could non say it and they did not know why they were holding that object. That led Sperry to conclude that the right hemisphere had some language recognition power, just no speech articulation, which meant that the right hemisphere could recognize or read a word, but it could not pronounce that word, so the person would not be able to say it or know what it was.

In his concluding serial of experiments in humans, Sperry showed ane object to the right center of the participants and some other object to their left eye. Sperry asked the volunteers to draw what they saw with their left hand only, with closed optics. All the participants drew the object that they saw with their left centre, controlled by the right hemisphere, and described the object that they saw with their right eye, controlled by the left hemisphere. That supported Sperry´s hypothesis that the hemispheres of brain functioned separately every bit two different brains and did non acknowledge the beingness of the other hemisphere, as the clarification of the object did non match the drawing. Sperry concluded that even though there were no apparent signs of disability in people with a severed corpus callosum, the hemispheres did not communicate, so information technology compromised the full function of the encephalon.

Sperry received the 1981 Nobel Prize in Physiology or Medicine for his split-encephalon enquiry. Sperry discovered that the left hemisphere of the brain was responsible for language understanding and joint, while the correct hemisphere could recognize a word, simply could not articulate it. Many researchers repeated Sperry´sf experiments to study the split-brain patterns and lateralization of office.

Sources

1. Sperry, Roger West. "Cerebral Arrangement and Behavior." Scientific discipline 133 (1961): 1749–57. http://people.uncw.edu/puente/sperry/sperrypapers/60s/85-1961.pdf (Access December 8, 2017).
2. Sperry, Roger Due west. "Hemisphere Deconnection and Unity in Witting Awareness." American Psychologist 28 (1968): 723–33. http://people.uncw.edu/Puente/sperry/sperrypapers/60s/135-1968.pdf (Access December 8, 2017).
3. Sperry, Roger W. "Split-encephalon Approach to Learning Issues." In The Neurosciences: A Study Program, eds. Gardner C. Quarton, Theodore Melnechuk, and Francis O. Schmitt, 714–22. New York: Rockefeller University Printing, 1967. ttp://people.uncw.edu/puente/sperry/sperrypapers/60s/130-1967.pdf (Accessed November15, 2017).
4. "The Separate Brain Experiments." Nobelprize.org. https://world wide web.nobelprize.org/educational/medicine/split-brain/background.html (Accessed May 3, 2017).

Lienhard, Dina A., "Roger Sperry'southward Separate Encephalon Experiments (1959–1968)". Embryo Projection Encyclopedia (2017-12-27). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/13035.

Arizona State University. Schoolhouse of Life Sciences. Center for Biology and Social club. Embryo Projection Encyclopedia.

Copyright Arizona Board of Regents Licensed as Creative Commons Attribution-NonCommercial-Share Alike 3.0 Unported (CC By-NC-SA 3.0) http://creativecommons.org/licenses/by-nc-sa/3.0/

Brain Mapping; Split-Brain Procedure; Brain; Epilepsy; Cerebral localization; corpus callosum; Separate Brain; Brain--Localization of functions; Studies of brain function; Homo brain part; corpus callosum; Cognitive localization; Experiment

morristhisicland67.blogspot.com

Source: https://embryo.asu.edu/pages/roger-sperrys-split-brain-experiments-1959-1968

Share this post