Dissociable distal and proximal motor components: Evidence from perseverative errors in three apraxic patients

In the present study we analysed the perseverative behaviour of three apraxic patients (FG, CEO, and VCR) while they were pantomiming the use of common objects and during their real use. The three patients were found to perseverate from one trial to later ones aspects of a given action in the pantomiming and in real use tasks. In particular, our main result was a striking double dissociation between patients in perseverating hand and arm movements. Patients FG and CEO made more perseveration errors involving the hand than VCR did, whereas the perseverative errors made by VCR involving the arm were more numerous than those made by FG and CEO. The patients differed also in other aspects of the perseverations, e.g., their median lags. Results are used to exend previous theories developed in the linguistic domain to that of actions.