An experimental investigation of the automatic/voluntary dissociation in limb apraxia

The ability of apraxic patients to perform gestures in everyday life is a controversial issue. In this paper, we aimed to evaluate the automatic/voluntary dissociation (AVD) in four patients affected by clinically relevant limb apraxia. For this purpose, we sampled different kinds of gestures belonging to patients' motor repertoire and then assessed their production in a testing session. Our experimental procedure consisted of two steps: in the first phase, we recorded gestures produced by patients in two natural conditions; in the second phase, we assessed production of correctly produced tool-actions, and of spontaneous non tool-actions and meaningless conversational (cohesive and beats) gestures under different modalities. AVD was observed for all types of gestures, albeit to different degree in single patients. The present findings demonstrate that the context provides strong bottom-up cues for the retrieval of motor patterns, while artificial testing conditions impose an additional cognitive load.