Editing Split-brain (section)

=== 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}}