Neurospychological Studie of the Mechanism of Higher Brain Function Using Brain Damaged Patients with Pure Syndrome

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We investigated many brain damaged patients including several types of pure syndrome and obtained following results.1)A 60-year-old, right-handen man suddenly developed severe pure word dumbness and slight dysgraphia. CT obtained in the second day of symptom shows a well defined old infarcrtion in the right frontal lobe. MRI reveals the lesion localized in the lower part of the precentrasl gyrus and pars opacularis of the third frontal gyrus, and also new infarction in the lower part of the left prefrontal gyrus. It is obvious that the first infarction in the right frontal lobe did not show any symptom and the second infarction occured in the similar parts of the-left hemisphere ca used severe pure word dumbness.2)Four prosopagnosic patients, two were bilateral and two were unilateral infarction in the teritory of the posterior cerebrtal artery, were investigated with several visuo-perceptual tests including familiar and unfamiliar faces. The results indecated that(1)the prosopagnosia can be occured as a isolated symptom without any other visuo-perceptual and vvisuo-cognitive deficits, (2)the prosopagnosia can be occured after unilateral right occipitotemporal lesion including lingual and fusiform gyrie. As the mechanism of the prosopagnosia, it was suggested that the memories of the familiar faces stored in the temporal visual association cortex were not activated by the visual inputs processed adequately in the visual cortices.Besides those patients we investigated several other patients including a pure alexic showing selective impairment of KANA reading, a left-hand apraxic and a patient with left-hand abnormal grasping both had a long and narrow infarction in the centrume semiovale along the longitudinal cerebral fissure, two patients with topographical memory loss after right unilateral infarction in the retrosplenial cortex etc.