Editing Split-brain (section)

== Case studies of split-brain patients ==

=== Patient WJ ===

Patient WJ was the first patient to undergo a full corpus callosotomy in 1962, after experiencing fifteen years of convulsions resulting from [[grand mal seizure]]s. He was a World War II paratrooper who was injured at 30 years old during a bombing raid jump over the Netherlands, and again in a prison camp following his first injury. After returning home, he began to suffer from blackouts in which he would not remember what he was doing or where, and how or when he got there. At age 37, he suffered his first generalized [[convulsion]]. One of his worst episodes occurred in 1953, when he suffered a series of convulsions lasting for many days. During these convulsions, his left side would go numb and he would recover quickly, but after the series of convulsions, he never regained complete feeling on his left side.<ref name = Eldridge>Eldridge, A. D. (n.d.). Discovering the unique individuals behind split-brain patient anonymity. Doctoral dissertation, University of North Carolina at Wilmington, Wilmington, NC. Retrieved from http://people.uncw.edu/puente/405/PDFpapers/Split-brain%20Patients.pdf {{Webarchive|url=https://web.archive.org/web/20160304102136/http://people.uncw.edu/puente/405/PDFpapers/Split-brain%20Patients.pdf |date=2016-03-04 }}</ref>

Before his surgery, both hemispheres functioned and interacted normally, his sensory and motor functions were normal aside from slight [[hypoesthesia]], and he could correctly identify and understand visual stimuli presented to both sides of his visual field. During his surgery in 1962, his surgeons determined that no [[massa intermedia]] had developed, and he had undergone [[atrophy]] in the part of the right frontal lobe exposed during the procedure. His operation was a success, in that it led to decreases in the frequency and intensity of his seizures.<ref name = Eldridge />

=== Patient JW ===

Funnell et al. (2007) tested patient JW some time before June 2006.<ref name = Funnellet2007>{{cite journal |author1=Funnell M. G. |author2=Colvin M. K. |author3=Gazzaniga M. S. | year = 2007 | title = The calculating hemispheres: Studies of a split-brain patient | journal = Neuropsychologia | volume = 45 | issue = 10| pages = 2378–2386 | doi=10.1016/j.neuropsychologia.2007.01.017 | pmid=17420034|s2cid=21620141 }}</ref> They described JW as

{{Blockquote
|text=a right-handed male who was 47 years old at the time of testing. He successfully completed high school and has no reported learning disabilities. He had his first seizure at the age of 16 and the age of 25, he underwent a two-stage resection of the corpus callosum for relief of intractable epilepsy. Complete sectioning of the corpus callosum has been confirmed by MRI.<ref name=":0">{{Cite journal|last1=Gazzaniga|first1=M. S.|last2=Holtzman|first2=J. D.|last3=Deck|first3=M. D.|last4=Lee|first4=B. C.|date=1985-12-01|title=MRI assessment of human callosal surgery with neuropsychological correlates|journal=Neurology|volume=35|issue=12|pages=1763–1766|issn=0028-3878|pmid=4069368|doi=10.1212/wnl.35.12.1763|s2cid=39978354}}</ref> Post-surgical MRI also revealed no evidence of other neurological damage.{{verify inline|reason=Citation seems misplaced. Is this text after the citation part of the quotation or not?|date=September 2023}}
}}

Funnell et al.'s (2007) experiments were to determine each of JW's hemisphere's ability to perform simple addition, subtraction, multiplication and division. For example, in one experiment, on each trial, they presented an arithmetic problem in the center of the screen for one second, followed by a central crosshair JW was to look at. After one more second, Funnell et al. presented a number to one or the other hemisphere / visual field for 150 ms—too fast for JW to move his eyes. Randomly in half the trials, the number was the correct answer; in the other half of the trials it was the incorrect answer. With the hand on the same side as the number, JW pressed one key if the number was correct and another key if the number was incorrect.<ref name = Funnellet2007 />

Funnell et al.'s results were that performance of the left hemisphere was highly accurate (around 95%)—much better than performance of the right hemisphere, which was at chance for subtraction, multiplication, and division. Nevertheless the right hemisphere showed better-than-chance performance for addition (around 58%).<ref>{{cite journal |last1=Funnell |first1=Margaret G. |title=The calculating hemispheres: studies of a split-brain patient |journal=Neuropsychologia |date=2007 |volume=45 |issue=10 |pages=2378–2386 |doi=10.1016/j.neuropsychologia.2007.01.017 |pmid=17420034 |s2cid=21620141 |url=https://www.sciencedirect.com/science/article/pii/S002839320700053X|url-access=subscription }}</ref>

Turk et al. (2002) tested hemispheric differences in JW's recognition of [[self-recognition|himself]] and of familiar faces.<ref>{{cite journal |author1=Turk D. J. |author2=Heatherton T. F. |author3=Kelley W. M. |author4=Funnell M. G. |author5=Gazzaniga M. S. |author6=Macrae C. N. | year = 2002 | title = Mike or me? Self-recognition in a split-brain patient | journal = Nature Neuroscience | volume = 5 | issue = 9| pages = 841–842 | doi = 10.1038/nn907 |pmid=12195428 |s2cid=36040335 }}</ref> They used faces that were composites of JW's face and Dr. Michael Gazzaniga's face. Composites ranged from 100% JW, through 50% JW and 50% Gazzaniga, to 100% Gazzaniga. JW pressed keys to say whether a presented face looked like him or Gazzaniga. Turk et al. concluded there are cortical networks in the left hemisphere that play an important role in self-recognition.{{citation needed|date=December 2020}}

=== Patient VP ===

Patient VP<ref>{{cite journal |author1=Funnell M. G. |author2=Corballis P. M. |author3=Gazzaniga M. S. | year = 2000 | title = Insights into the functional specificity of the human corpus callosum | journal = Brain | volume = 123 | issue = 5| pages = 920–926 | doi=10.1093/brain/123.5.920|pmid=10775537 | doi-access = free }}</ref> is a woman who underwent a two-stage callosotomy in 1979 at the age of 27. Although the callosotomy was reported to be complete, a follow-up MRI in 1984 revealed spared fibers in the rostrum and splenium. The spared rostral fibers constituted approximately 1.8% of the total cross-sectional area of the corpus callosum and the spared splenial fibers constituted approximately 1% of the area.<ref name=":0" /> VP's postsurgery intelligence and memory quotients were within normal limits.<ref>{{cite journal |vauthors=Gazzaniga MS, Nass R, Reeves A, Roberts D | year = 1984 | title = Neurologic perspectives on right hemisphere language following surgical section of the corpus callosum | journal = Seminars in Neurology | volume = 4 | issue = 2| pages = 126–135 | doi=10.1055/s-2008-1041542| s2cid = 260318839 }}</ref>

One of the experiments involving VP attempted to investigate systematically the types of visual information that could be transferred via VP's spared splenial fibers. The first experiment was designed to assess VP's ability to make between-field perceptual judgments about simultaneously presented pairs of stimuli. The stimuli were presented in varying positions with respect to the horizontal and vertical midline with VP's vision fixated on a central crosshair. The judgments were based on differences in color, shape or size. The testing procedure was the same for all three types of stimuli; after presentation of each pair, VP verbally responded "yes" if the two items in the pair were identical and "no" if they were not. The results show that there was no perceptual transfer for color, size or shape with binomial tests showing that VP's accuracy was not greater than chance.{{citation needed|date=December 2020}}

A second experiment involving VP attempted to investigate what aspects of words transferred between the two hemispheres. The set up was similar to the previous experiment, with VP's vision fixated on a central crosshair. A word pair was presented with one word on each side of the crosshair for 150 ms. The words presented were in one of four categories: words that looked and sounded like rhymes (e.g. tire and fire), words that looked as if they should rhyme but did not (e.g. cough and dough), words that did not look as if they should rhyme but did (e.g. bake and ache), and words that neither looked nor sounded like rhymes (e.g. keys and fort). After presentation of each word pair, VP responded "yes" if the two words rhymed and "no" if they did not. VP's performance was above chance and she was able to distinguish among the different conditions. When the word pairs did not sound like rhymes, VP was able to say accurately that the words did not rhyme, regardless of whether or not they looked as if they should rhyme. When the words did rhyme, VP was more likely to say they rhymed, particularly if the words also looked as if they should rhyme.{{citation needed|date=December 2020}}

Although VP showed no evidence for transfer of color, shape or size, there was evidence for transfer of word information.<ref>{{cite journal | last = Gazzaniga |first=M. S. | year = 2000 | title = Cerebral specialization and interhemispheric communication | journal = Brain | volume = 123 | issue = 7| pages = 1293–1326 | doi = 10.1093/brain/123.7.1293 | pmid = 10869045 | doi-access = free }}</ref> This is consistent with the speculation that the transfer of word information involves fibers in the ventroposterior region of the [[splenium]]—the same region in which VP had callosal sparing. VP is able to integrate words presented to both visual fields, creating a concept that is not suggested by either word. For example, she combines "head" and "stone" to form the integrated concept of a tombstone.{{citation needed|date=December 2020}}

=== Kim Peek ===

[[Kim Peek]]<ref>{{cite journal |last1=Treffert |first1=D. A. |last2=Christensen |first2=D. D. | year = 2006 | title = Inside the mind of a savant | journal = Scientific American Mind | volume = 17 | issue = 3| pages = 52–55 | doi = 10.1038/scientificamericanmind0606-50 |s2cid=1844071 }}</ref> was arguably the most well-known [[savant syndrome|savant]]. He was born on November 11, 1951, with an enlarged head, [[encephalocele|sac-like protrusions]] of the brain and the membranes that cover it through openings in the skull, a malformed [[cerebellum]], and without a corpus callosum, an anterior commissure, or a posterior commissure. He was able to memorize over 9,000 books, and information from approximately 15 subject areas. These include: world/American history, sports, movies, geography, actors and actresses, the Bible, church history, literature, classical music, area codes/zip codes of the United States, television stations serving these areas, and step-by-step directions within any major U.S. city. Despite these abilities, he had an IQ of 87, was diagnosed as autistic, was unable to button his shirt, and had difficulties performing everyday tasks. The missing structures of his brain have yet to be linked to his increased abilities, but they can be linked to his ability to read pages of a book in 8–10 seconds. He was able to view the left page of a book with his left visual field and the right page of a book with his right visual fields so he could read both pages simultaneously.<ref name="psychologytoday.com">{{cite web |last=Brogaard |first=B. |date=November 6, 2012 |title=The superhuman mind: Split brains |access-date=April 26, 2014 |website=Psychology Today |url=http://www.psychologytoday.com/blog/the-superhuman-mind/201211/split-brains}}</ref> He also had developed language areas in both hemispheres, something very uncommon in split-brain patients. [[Language]]<ref name="psychologytoday.com"/> is processed in areas of the left temporal lobe, and involves a [[contralateral]] transfer of information before the brain can process what is being read. In Peek's case, there was no transfer ability—this is what led to his development of language centers in each hemisphere. 

Although Peek did not undergo corpus callosotomy, he is considered a natural split-brain patient and is critical to understanding the importance of the corpus callosum. Kim Peek died in 2009.<ref name="psychologytoday.com"/>