Retrieval by a patient with apraxia of sensorimotor information from visually presented objects.

Motor representations are reported to be implicitly evoked when one observes manipulatable objects (action potentiation). The relationship was examined between action potentiation and pantomime deficit in apraxia. Participants responded to line drawings of manipulatable objects with either the left or right hand, according to the color of the stimulus. In normal participants (N= 10, four women, six men, M age = 28.5 yr., SD = 5.6), responses were faster when the orientation of the stimulus was compatible with the response-hand grasp. However, the apraxic patient did not exhibit this compatibility effect. On a control task in which a nonobject (circle) was presented, all participants exhibited the compatibility effect. These results indicated that the apraxic patient was impaired in evoking motor representation associated with objects. Thus, in some cases, apraxic disorders may be attributable to a deficit in retrieving object-specific information for manipulation.