Causative role of left aIPS in coding shared goals during human-avatar complementary joint actions

Successful motor interactions require agents to anticipate what a partner is doing in order to predictively adjust their own movements. Although the neural underpinnings of the ability to predict others' action goals have been well explored during passive action observation, no study has yet clarified any critical neural substrate supporting interpersonal coordination during active, non-imitative (complementary) interactions. Here, we combine non-invasive inhibitory brain stimulation (continuous Theta Burst Stimulation) with a novel human-avatar interaction task to investigate a causal role for higher-order motor cortical regions in supporting the ability to predict and adapt to others' actions. We demonstrate that inhibition of left anterior intraparietal sulcus (aIPS), but not ventral premotor cortex, selectively impaired individuals' performance during complementary interactions. Thus, in addition to coding observed and executed action goals, aIPS is crucial in coding 'shared goals', that is, integrating predictions about one's and others' complementary actions

Inhibition of left anterior intraparietal sulcus shows that mutual adjustment marks dyadic joint-actions in humans

Creating real-life dynamic contexts to study interactive behaviors is a fundamental challenge for the social neuroscience of interpersonal relations. Real synchronic interpersonal motor interactions involve online, inter-individual mutual adaptation (the ability to adapt one's movements to those of another in order to achieve a shared goal). In order to study the contribution of the left anterior Intra Parietal Sulcus (aIPS) (i.e. a region supporting motor functions) to mutual adaptation, here, we combined a behavioral grasping task where pairs of participants synchronized their actions when performing mutually adaptive imitative and complementary movements, with the inhibition of activity of aIPS via non-invasive brain stimulation. This approach allowed us to investigate whether aIPS supports online complementary and imitative interactions. Behavioral results showed that inhibition of aIPS selectively impairs pair performance during complementary compared to imitative interactions. Notably, this effect depended on pairs' mutual adaptation skills and was higher for pairs composed of participants who were less capable of adapting to each other. Thus, we provide the first causative evidence for a role of the left aIPS in supporting mutually adaptive interactions and show that the inhibition of the neural resources of one individual of a pair is compensated at the dyadic level

Interpersonal motor interactions shape multisensory representations of the peripersonal space

This perspective review focuses on the proposal that predictive multisensory integration occurring in one’s peripersonal space (PPS) supports individuals’ ability to efficiently interact with others, and that integrating sensorimotor signals from the interacting partners leads to the emergence of a shared representation of the PPS. To support this proposal, we first introduce the features of body and PPS representations that are relevant for interpersonal motor interactions. Then, we highlight the role of action planning and execution on the dynamic expansion of the PPS. We continue by presenting evidence of PPS modulations after tool use and review studies suggesting that PPS expansions may be accounted for by Bayesian sensory filtering through predictive coding. In the central section, we describe how this conceptual framework can be used to explain the mechanisms through which the PPS may be modulated by the actions of our interaction partner, in order to facilitate interpersonal coordination. Last, we discuss how this proposal may support recent evidence concerning PPS rigidity in Autism Spectrum Disorder (ASD) and its possible relationship with ASD individuals’ difficulties during interpersonal coordination. Future studies will need to clarify the mechanisms and neural underpinning of these dynamic, interpersonal modulations of the PPS

Competence-based social status and implicit preference modulate the ability to coordinate during a joint grasping task

Studies indicate that social status influences people’s social perceptions. Less information is available about whether induced social status influences dyadic coordination during motor interactions. To explore this issue, we designed a study in which two confederates obtained high or low competence-based status by playing a game together with the participant, while the participant always occupied the middle position of the hierarchy. Following this status-inducing phase, participants were engaged in a joint grasping task with the high- and low-status confederates in different sessions while behavioural (i.e., interpersonal asynchrony and movement start time) indexes were measured. Participants’ performance in the task (i.e., level of interpersonal asynchrony) when interacting with the low-status partner was modulated by their preference for him. The lower participants’ preference for a low- relative to a high-status confederate, the worse participants’ performance when interacting with the low-status confederate. Our results show that participants’ performance during motor interactions changes according to the social status of the interaction partner