Split brain surgery: effects and neurological outcomes

Split Brain Surgery: History And Scientific Overview

"Even more startling was Paul's ability to write answers to questions asked of his right half-brain. Instead of wondering whether or not Paul's right hemisphere was sufficiently powerful to be dubbed conscious, we were now in a position to ask Paul's right side about its views on matters of friendship, love, hate, and aspirations. 'Who are you?' He writes: 'Paul.' 'Where are you?' He writes: 'Vermont.' 'What do you want to be?' He writes: 'Automobile racer.' When the left hemisphere was asked this same question, he wrote (with his right hand), 'Draftsman"(Split brain consciousness, 2010, Macalester University)

What could explain Paul's perplexing behavior? Despite Paul's completely different answers to the same questions, asked within minutes of one another, Paul was neither delusional nor suffering from a split personality. However, as a recipient of split brain surgery, Paul's consciousness had undergone a fundamental alteration. His left and right brain hemispheres had developed two different 'selves' with two different opinions.

Split-brain surgery, or the severing of the corpus callosum, is a procedure used to treat severe epilepsy in extreme instances when the afflicted individual does not respond to medication or other treatments. An epileptic seizure is the result of abnormal neurons in the patient's brain 'firing' or sending uncontrollable signals to other neurons. Eventually this will cause other neurons to also begin firing, generating a grand mal seizure. The corpus callosum connects the left and right hemispheres, allowing both sides of the brain to communicate with one another. "When a split-brain surgery is performed, the left and right hemispheres can no longer fully send messages to one another" and thus the epileptic seizures cease or are greatly reduced in intensity (Palmer 2003). Preventing the left and right hemispheres from communicating reduces the severity of the seizures by preventing the storm of firing neurons from moving from one side of the brain to the other side of the brain.

The surgery was not the only type of surgery used to treat epilepsy but initially proved successful as a means of treatment. Surgeons tried to do the surgery in as noninvasive a manner as possible, first severing only a few connections, and then taking more radical action and cutting all connections. The surgery was first developed by Roger Sperry and Ronald Meyers in the late 1950's. Initially Sperry and Meyers began experimenting with cats, and later proceeded to study monkeys. In 1961 the first human patient was subject to the surgery. However, some unanticipated results occurred that could not have been discovered, when Sperry and Meyers were only testing the responses of cats.

Post-surgery, the surgery recipients initially appeared to be unaffected. However, when tested, the patients exhibited abnormal responses regarding their ability to process language: "In one experiment, a word (for example 'fork') was flashed so only the right hemisphere of a patient could receive the information. The patient would not be able to say what the word was. However, if the subject is asked to write what he saw, his left hand would begin to write the word 'fork'. If asked what he had written, the patient would have no idea. He would know that he had written something, he could feel his hand going through the motion, yet he could not tell observers what the word was" because his capacity for producing and processing language had been damaged (A brief history, 2010, Macalester University).

Split brain operations unintentionally provided important clues about hemispheric activity and the brain. The results of the experiment demonstrated that the left brain generally assumes the responsibility of language-related functions. The left brain was also shown to be dominant in figuring out logic-related puzzles and details, while the right was dominant for interpreting spatial relationships and 'big picture' issues. The right brain also plays a role in interpreting emotions: split brain surgery recipients often suffered from problems interpreting faces and speaking about their emotions. However, it is important to note that although this left and right distinction is true for most individuals, the right brain is not necessarily nonverbal, particularly for left-handed people: "In over 95% of right-handed people the left hemisphere is dominant for speech. The figure is somewhat lower for left handers, approximately 70%" (Hemisphere specialization, 2010, Macalester University).

The fact that some people's right hemispheres do possess the ability to 'speak' enabled further illuminating results to be generated by studying split brain patients: in the case of one split brain operation patient 'Paul,' for example, Paul's right hemisphere was able to express itself alone: "Paul's right hemisphere stated that he wanted to be an automobile racer while his left hemisphere wanted to be a draftsman" (Behavior, 2010, Macalester University). It was as if Paul's different hemispheres had different personalities, even different political opinions. The left side of the brain controls the right side of the individual's body and the right side controls the left hand. Paul wrote with his right-dominated left hand that he wanted to be a presumably exciting occupation -- and that he hated Richard Nixon. The left side, using the right hand said he would prefer a more practical occupation, and expressed a more balanced view of Nixon.

Not all patients' right sides were as verbal as Paul's, and some patients merely experienced difficulty in emotional expressiveness. Other accounts of post-surgery behavior were extremely disturbing in terms of patient's development of split identities. One patient "would sometimes find himself pulling his pants down with one hand and pulling them up with the other. Once, he grabbed his wife with his left hand and shook her violently, with the right hand trying to come to his wife's aid in bringing the left belligerent hand under control. Once, while I [the patient's doctor] was playing horseshoes with the patient in his backyard, he happened to pick up an ax with his left hand. Because it was entirely likely that the more aggressive right hemisphere might be in control, I discretely left the scene-not wanting to be the victim for the test case of which half-brain does society punish or execute," said the doctor who performed the procedure (Dewey 2010).