Neurosychological Studies of the Relation between Lesion Localization by MRI and the Disorders of Higher Brain Functions.

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The relation between neurological signs and symptoms and computed tomography (CT) and magnetic resonance imaging (MRI) was examined in 11 cases of pure alexia. The results revealed that lesions of the inferior occipital cortex (lingual and fusiform gyri) and the subjacent white matter of the left hemisphere were necessary and sufficient to produce pure alexia. And contrary to conventional view, it is suggested that pure alexia may occur without lesions of the corpus callosum.Also many patients with various neurological signs and symptoms were examined. Among them, the important and the most interest cases were as follows: 1.a patient with left unilateral agraphia for kanji but not for kana: This patient was diagnosed by MRI as having a lesion of the posterior body of the corpus callosum, and it is suggested that different neural pathways are used for kanji and kana not only intrahemispherically but also interhemispherically. 2.a case with pure word deafness: This patient was diagnosed by MRI as having a lesion of the subcortical area in left temporoparietal cortex with intact Wernicke's area. From this lesion, it is suggested that the pure word deafness occurred as the isolation of Wernicke's area from auditory information by the associated disconnection of the left auditory radiation and the callosal pathway from the right auditory cortex.