Verbal commands help the execution of endogenous movements in anarchic hand

Patients with anarchic hand (AH) syndrome exhibit involuntary but seemingly purposeful controlesional upper limb movements. Here we report on the case of a patient (AC) presenting with a right AH following a left medial frontal lesion. Previous literature indicated that endogenous movements, particularly in the presence of distractors, are impaired in AH, whereas exogenous movements are spared. In this study we examined exogenous and endogenous (or sequential) movements using a new experimental procedure. Our main aim was to investigate whether the ability to perform sequential movements improves under verbal command as anecdotally observed in patients with AH. Results showed that the performance of AC's right AH was impaired in sequential tasks and that this impairment was improved by verbal command. The observed reduction in errors in sequential tasks under external verbal command was coupled with a compensatory increase in response times.