How Task Interactivity Shapes Action Observation

Abstract

Action observation triggers imitation, a powerful mechanism permitting interpersonal coordination. Coordination, however, also occurs when the partners’ actions are nonimitative and physically incongruent. One influential theory postulates that this is achieved via top-down modulation of imitation exerted by prefrontal regions. Here, we rather argue that coordination depends on sharing a goal with the interacting partner: this shapes action observation, overriding involuntary imitation, through the predictive activity of the left ventral premotor cortex (lvPMc). During functional magnetic resonance imaging (fMRI), participants played music in turn with a virtual partner in interactive and noninteractive conditions requiring 50% of imitative/nonimitative responses. In a full-factorial design, both perceptual features and low-level motor requirements were kept constant throughout the experiment. Behaviorally, the interactive context minimized visuomotor interference due to the involuntary imitation of physically incongruent movements. This was paralleled by modulation of neural activity in the lvPMc, which was specifically recruited during the interactive task independently of the imitative/nonimitative nature of the social exchange. This lvPMc activity reflected the predictive decoding of the partner’s actions, as revealed by multivariate pattern analysis. This demonstrates that, during interactions, we process our partners’ behavior to prospectively infer their contribution to the shared goal achievement, generating motor predictions for cooperation beyond low-level imitation.

Mechanisms for mutual support in motor interactions

“…The present findings also replicate our previous observations on the effect of task interactivity on action observation and its impact on the agent's behavior, which we demonstrated in adults 15,16 (see 40 for an independent Table 3. The Table illustrates, per each melody, what a sequence with Action-and Goal-Errors looked like.…”

“…Accordingly, having a playbook in mind would trigger specific expectations of the team-mates' upcoming behavior. This interpretation would be in line with our and others' suggestion that one's and the partner's actions are integrated within a dyadic motor plan (DMP 15,16 , Fig. 1b), resembling what happens for left-and right-hand movements during bimanual coordination [17][18][19][20] .…”

“…60 . Specifically, in the present paradigm, the left ventral premotor cortex might play a critical role 16 , because it is responsible for goal predictions for hand movements in humans 61,62 and non-human primates 63,64 .…”

“…49 ). While physical congruence of actions interferes with motor execution when the partner's action outcome is irrelevant and no expectation is present 15,16 , the outcome and the ensuing action-outcome associations are taken into account during interactions (see also Ref. 50 ), possibly requiring additional neural resources.…”

“…Experimental tasks (Joint Action vs. Non-Interactive) 15,16 . There were separate sessions for the Joint Action (JA) and Non-Interactive (Non-Int) tasks, which were presented in counterbalanced order between the participants.…”