Apraxia is not associated to a disproportionate naming impairment for manipulable objects

The relevance of gesture knowledge for the semantic representation of manipulable objects was investigated in a series of 15 patients with a focal left-hemisphere lesion. The patients were classified according to the presence/absence of ideomotor and ideational apraxia. We investigated picture naming and word-picture matching (pointing to a picture on verbal command) with stimuli including items from three categories: manipulable objects, non-manipulable objects, and animals. The analysis was performed at group level and at single-patient level. Nine patients were affected by ideational apraxia and nine by ideomotor apraxia: two cases presented ideomotor but not ideational apraxia, and two cases presented the opposite dissociation. Patients affected by ideational apraxia were more severely impaired in all tasks, but did not show a disproportionate impairment with the category of manipulable objects in contrast to the other categories. The presence of ideomotor apraxia did not cause a greater impairment in any task or category. Finally, we observed a patient with ideational apraxia who performed flawlessly in naming and word-picture matching for all the stimuli, including manipulable objects. In conclusion, we did not find a relationship between ideational apraxia and a disproportionate impairment of the semantic knowledge of manipulable objects.