Ideational apraxia and naturalistic action

It is frequently claimed that ideational apraxia, an impairment of the performance of complex actions with objects, is a left-hemisphere syndrome. We assessed the consequences of left-hemisphere damage for naturalistic action performance in two studies. In Study 1, we compared the action errors of left-hemisphere stroke patients (LCVA) to previously reported patients with right-hemisphere stroke (RCVA) and closed head injury (CHI), and found that LCVA were no more vulnerable to errors of action than the other patient groups once differences in severity were controlled. In Study 2, we compared the naturalistic action performance of a patient with severe ideational apraxia and left-hemisphere damage to that of two RCVA patients of equal clinical severity. There was considerable quantitative and qualitative similarity in the errors of the three patients. From these-and other findings, we argue that deficits in left-hemisphere systems do not compromise complex action in a unique or transparent manner. We offer an alternative account based on nonspecific resource limitations that accommodates the data from all patient groups.