Conduction aphasia is a subtype of aphasia whose core disturbances are in the processing of phonological mapping. We have observed eight cases of conduction aphasia during the past 10 years. Five subjects were right-handed and the rest were not right-handed. Six subjects had been affected in the left hemisphere, and the rest in the right hemisphere. We studied their lesions by MRI, CT and/or SPECT, and evaluated the neuropsychological symptoms in each subject. The results were as follows. (1)The five right-handed subjects who had damage in the left hemisphere exhibited a common lesion in the supra marginal gyrus, suggesting that in humans with “normal” cerebral lateralization the center for phonological mapping is in the supra marginal gyrus. (2)Results for the three non-right-handed subjects thought to have “anomalous” cerebral lateralization suggested that among the subcomponents of language processing, the phonological mapping system is able to localize independently in either hemisphere. (3)All subjects showed buccofacial apraxia, suggesting that phonological mapping and buccofacial praxis have some compatibility in terms of localization in the brain.
