Common dimensions of visual and auditory agnosia and an explanation of the auditory recognition deficit in aphasia.
An experimental analysis of auditory recognition disturbances was performed; 81 patients with localized cerebral lesions were examined with a recognition test for meaningful sounds and with a nonverbal intelligence test (Block Design). Sensory stimulation was 5 or 15 sec for each sound. Nonverbal intelligence accounted for a considerable and significant amount of variance in recognition performance. The aphasic group was more impaired in auditory recognition than were both the other groups, i.e., patients with right or left hemispheric lesions without aphasia. The auditory recognition disturbance in the aphasic group depended to a significant extent on stimulus duration, which means a slowing down of the recognition process in aphasia. The analogies to studies on visual agnosia are striking. In both modalities, recognition depends on intellectual functioning, sensory disturbances or reduced sensory input, and the presence of aphasia.