<P> Experiments on covert orienting of spatial attention using the Posner paradigm confirm the existence of two different attentional systems in the two hemispheres . The right hemisphere was found superior to the left hemisphere on modified versions of spatial relations tests and in locations testing, whereas the left hemisphere was more object based . The components of mental imagery are differentially specialized: the right hemisphere was found superior for mental rotation, the left hemisphere superior for image generation . It was also found that the right hemisphere paid more attention to landmarks and scenes whereas the left hemisphere paid more attention to exemplars of categories . </P> <P> Patient W.J. was the first patient to undergo a full corpus callosotomy in 1962, after undergoing fifteen years of convulsions resulting from grand mal seizures . 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 . </P> <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 great success, leading to a decrease 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>

Who conducted the first experiments using split-brain patients