<P> Before his surgery, both hemispheres functioned and interacted normally, his sensory and motor functions were normal aside from slight hypesthesia, 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 . </P> <P> Patient JW is 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 . At 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 . Post-surgical MRI also revealed no evidence of other neurological damage . </P> <P> One of the experiments involving JW attempted to determine each hemisphere's ability to perform simple addition, subtraction, multiplication and division . On each trial, an arithmetic problem was presented in the center of the screen followed by a central cross hair . After studying the problem, a number posing as the answer was presented to each hemisphere exclusively by JW's vision fixated on a central cross hair . Probes (stimuli) were then presented for 150 ms to either the left visual field / right hemisphere (LVF / RH) or to the right visual field / left hemisphere (RVF / LH). The position of the probe fell outside any zone of naso - temporal overlap (binocular vision) to ensure that stimuli were perceived only by the hemisphere contralateral to the visual field of the stimuli . JW was instructed to press a certain key if the probe was the correct solution and another key if the probe was the incorrect solution . Results showed that the effects of visual field was significant with performance of the left hemisphere being better than that of the right hemisphere; the left hemisphere correctly chose the correct answer on all four arithmetic operations approximately 90% of the time while the right hemisphere was at chance . These results suggest left hemisphere specialization for calculation . </P> <P> J.W. was further tested to determine after - effects on his self - recognition and familiar facial recognition . He was tested in a study where he would respond yes or no to images presented, by pressing a button . These images were ranging from 0--100% "JW", with the 0% images being of Dr. Michael Gazzaniga, and the 100% images being of J.W. himself . What researchers found supported the idea that there are cortical networks in the left hemisphere that play an important role in execution of the self - recognition process . </P>

If the corpus callosum is severed how might this affect the way that we perceive the world