Two forms of ideomotor apraxia.

Destruction of parietal areas containing visuokinesthetic motor engrams, where motor acts may be programmed, should be distinguishable from apraxia induced by disconnection of these parietal areas from frontal motor areas. Destruction should result in inability to distinguish well-performed from poorly performed movements, whereas disconnection should not. We gave movement and act-discrimination tasks to apraxic and nonapraxic patients with anterior lesions or nonfluent aphasia, and to patients with posterior lesions or fluent aphasia. On both tasks, the performance of posterior/fluent patients was worse than that of all other patients. Our results suggest that there are two types of patients with ideomotor apraxia.