Dissociation of visual and auditory language comprehension capacity in aphasia

Visual language comprehension capacity was compared with auditory language comprehension capacity in 26 aphasic subjects. The Token Test was used for both modalities. By the means of the difference in scores on the two tests three groups were separated, that is (1) a group with no essential difference between the two capacities, (2) a group with superior reading capacity and (3) a group with superior auditory capacity. Particular attention was directed to the second group. Seven subjects showed this type of dissociated comprehension. The group was found to be heterogeneous in their linguistic characteristics. The clinical type of aphasia included not only Wernicke's aphasia but also Broca's aphasia. A possible psychological explanation underlying this phenomenon was attempted. Anatomical correlation was also attempted. The hypothesis of sparing the left inferior parietal lobe is proposed as an explanation of why visual comprehension was better preserved than auditory comprehension.