The right hemisphere and optic aphasia/optic apraxia

Abstract

We describe a patient with inordinate impairment in oral picture naming (as opposed to oral naming to definitions and viewed gestures). His naming errors were primarily semantically related or perseverative responses. He also had greater difficulty gesturing in response to viewed pictures than gesturing to verbal commands, and produced many semantic and perseverative gesture errors. He performed relatively well in some visual tasks (e.g. matching, object decision, and drawing), but was impaired on others (e.g. copying pictures). He had intact abilities for basic semantic processing of pictures (category sorting, cross-modal matching), but he demonstrated impairment in picture comprehension tasks requiring more detailed semantic information (matching associated pictures). We propose that this patient's impairment may be classified as optic aphasia and optic apraxia, and not visual associative agnosia in which we expect greater recognition Impairment. Current cognitive models that attempt to explain optic aphasia would have difficulty accounting entirely for this patient's impairments. We suggest that the information gained from right hemisphere visual processing is unable fully to activate and specify phonological and gestural output representations in the left hemisphere, either directly or by way of right hemisphere semantic processing.