Neuro-cognitive and social components of dyadic motor interactions revealed by the kinematics of a joint-grasping task

This thesis describes a PhD project is based on the notion that we live our whole life dipped into an interactive social environment where we observe and act together with others and where our behavior is influenced by first sight impressions, social categorizations and stereotypes which automatically and unavoidably arise during interactions. Nevertheless, the bidirectional impact of interpersonal coding on dyadic motor interactions has never been directly investigated. Moreover, the neurocognitive bases of social interaction are still poorly understood. In particular, in every-day dyadic encounters we usually interact with others in non-imitative fashions (Sebanz et al. 2006), challenging the hypothesis of a direct matching between action observation and action execution within one system (“common coding approach”, Prinz 1997), which is instead supported by neurophysiological data on the so called “mirror neurons”(Rizzolatti and Sinigaglia 2010) which fire both during action execution and observation of similar actions performed by others. Suggestion is made that what characterizes joint action is the presence of a common goal (i.e. the “shared” goal, Butterfill 2012) which organizes individuals’ behaviour and channel simulative processes. During her PhD, Lucia Sacheli developed a novel interactive scenario able to investigate face-to-face dyadic interactions within a naturalistic and yet controlled experimental environment, with the aim to build a more coherent model of the role of simulative mechanisms during social interaction and on the role of socio-emotional variables in modulating these processes. This scenario required pairs of participants to reciprocally coordinate their reach-to-grasp movements and perform on-line mutual adjustments in time and space in order to fulfill a common (motor) goal. So far, she demonstrated by means of kinematic data analysis that simulation of the partner’s movement is task-dependent (Sacheli et al. 2013) and modulated by the interpersonal relationship linking co-agents (Sacheli et al. 2012) and by social stereotypes as ethnic biases (Sacheli et al. under review). Moreover, she used the same scenario to investigate the different contribution of the parietal and frontal nodes of the fronto-parietal “mirror” network during joint-action by means of Transcranial Magnetic Stimulation combined with analysis of kinematics

Neuro-cognitive and social components of dyadic motor interactions revealed by the kinematics of a joint-grasping task

This thesis describes a PhD project is based on the notion that we live our whole life dipped into an interactive social environment where we observe and act together with others and where our behavior is influenced by first sight impressions, social categorizations and stereotypes which automatically and unavoidably arise during interactions. Nevertheless, the bidirectional impact of interpersonal coding on dyadic motor interactions has never been directly investigated. Moreover, the neurocognitive bases of social interaction are still poorly understood. In particular, in every-day dyadic encounters we usually interact with others in non-imitative fashions (Sebanz et al. 2006), challenging the hypothesis of a direct matching between action observation and action execution within one system (“common coding approach”, Prinz 1997), which is instead supported by neurophysiological data on the so called “mirror neurons”(Rizzolatti and Sinigaglia 2010) which fire both during action execution and observation of similar actions performed by others. Suggestion is made that what characterizes joint action is the presence of a common goal (i.e. the “shared” goal, Butterfill 2012) which organizes individuals’ behaviour and channel simulative processes. During her PhD, Lucia Sacheli developed a novel interactive scenario able to investigate face-to-face dyadic interactions within a naturalistic and yet controlled experimental environment, with the aim to build a more coherent model of the role of simulative mechanisms during social interaction and on the role of socio-emotional variables in modulating these processes. This scenario required pairs of participants to reciprocally coordinate their reach-to-grasp movements and perform on-line mutual adjustments in time and space in order to fulfill a common (motor) goal. So far, she demonstrated by means of kinematic data analysis that simulation of the partner’s movement is task-dependent (Sacheli et al. 2013) and modulated by the interpersonal relationship linking co-agents (Sacheli et al. 2012) and by social stereotypes as ethnic biases (Sacheli et al. under review). Moreover, she used the same scenario to investigate the different contribution of the parietal and frontal nodes of the fronto-parietal “mirror” network during joint-action by means of Transcranial Magnetic Stimulation combined with analysis of kinematics

Transitory Inhibition of the left anterior intraparietal sulcus impairs joint actions: a continuous Theta-Burst stimulation study

Although temporal coordination is a hallmark of motor interactions, joint action (JA) partners do not simply synchronize; they rather dynamically adapt to each other to achieve a joint goal. We created a novel paradigm to tease apart the processes underlying synchronization and JA and tested the causal contribution of the left anterior intraparietal sulcus (aIPS) in these behaviors. Participants had to synchronize their congruent or incongruent movements with a virtual partner in two conditions: (i) being instructed on what specific action to perform, independently from what action the partner performed (synchronization), and (ii) being instructed to adapt online to the partner's action (JA). Offline noninvasive inhibitory brain stimulation (continuous theta-burst stimulation) over the left aIPS selectively modulated interpersonal synchrony in JA by boosting synchrony during congruent interactions and impairing it during incongruent ones, while leaving performance in the synchronization condition unaffected. These results suggest that the left aIPS plays a causal role in supporting online adaptation to a partner's action goal, whereas it is not necessarily engaged in social situations where the goal of the partner is irrelevant. This indicates that, during JAs, the integration of one's own and the partner's action goal is supported by aIPS

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

Autistic traits affect interpersonal motor coordination by modulating strategic use of role-based behavior

Background: Despite the fact that deficits in social communication and interaction are at the core of Autism Spectrum Conditions (ASC), no study has yet tested individuals on a continuum from neurotypical development to autism in an on-line, cooperative, joint action task. In our study, we aimed to assess whether the degree of autistic traits affects participants' ability to modulate their motor behavior while interacting in a Joint Grasping task and according to their given role. Methods: Sixteen pairs of adult participants played a cooperative social interactive game in which they had to synchronize their reach-to-grasp movements. Pairs were comprised of one ASC and one neurotypical with no cognitive disability. In alternate experimental blocks, one participant knew what action to perform (instructed role) while the other had to infer it from his/her partner’s action (adaptive role). When in the adaptive condition, participants were told to respond with an action that was either opposite or similar to their partner. Participants also played a non-social control game in which they had to synchronize with a non-biological stimulus. Results: In the social interactive task, higher degree of autistic trait s predicted less ability to mod ulate joint action according to one’s interactive role. In the non-social task, autistic traits did not predict differences in movement preparation and planning, thus ruling out the possibility that social interact ive task results were due to basic motor or executive function difficulties. Furthermore, when participants played the non-social game, the higher their autistic traits, the more they were interfered by the non-biological stimulus. Conclusions: Our study shows for the first time that high autistic traits predict a stereotypical interaction style when individuals are required to modulate their movements in order to coordinate with their partner according to their role in a joint action task. Specifically, the infrequent emergence of role-based motor behavior modulation during on-line motor cooperation in participants with high autistic traits sheds light on the numerous difficulties ASC have in nonverbal social interaction

Kinematics fingerprints of leader and follower role-taking during cooperative joint actions

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Interactional leader-follower sensorimotor communication strategies during repetitive joint actions

Non-verbal communication is the basis of animal interactions. In dyadic leader – follower interactions, leaders master the ability to carve their motor behaviour in order to ‘signal’ their future actions and internal plans while these signals influence the behaviour of follower partners, who automatically tend to imitate the leader even in complementary interactions. Despite their usefulness, signalling and imitation have a biomechanical cost, and it is unclear how this cost – benefits trade-off is managed during repetitive dyadic interactions that present learnable regularities. We studied signalling and imitation dynamics (indexed by movement kinematics) in pairs of leaders and followers during a repetitive, rule-based, joint action. Trial-by-trial Bayesian model comparison was used to evaluate the relation between signalling, imitation and pair performance. The different models incorporate different hypotheses concerning the factors (past interactions versus online movements) influencing the leader’s signalling (or follower’s imitation) kinematics. This approach showed that (i) leaders’ signalling strategy improves future couple performance, (ii) leaders used the history of past interactions to shape their signalling, (iii) followers’ imitative behaviour is more strongly affected by the online movement of the leader. This study elucidates the ways online sensorimotor communication help individuals align their task representations and ultimately improves joint action performanc

Antifungal Resistance in Dermatophytes: Genetic considerations, Clinical Presentations and Alternative Therapies

Numerous reports describe the emergence of resistance in dermatophytes, especially in T. rubrum and T. mentagrophytes/indotineae strains. We here present a review of the current status of resistance in dermatophytes worldwide. Resistance to terbinafine is mainly discussed, with dif-ferent mutations found in the squalene epoxidase gene also considered. Resistance to azoles is also approached. Clinical presentations caused by resistant dermatophytes are presented, to-gether with alternative therapies that help to better manage these kind of infections

And yet they act together: Interpersonal perception modulates visuo-motor interference and mutual adjustments during a joint-grasping task

Prediction of “when” a partner will act and “what” he is going to do is crucial in joint-action contexts. However, studies on face-to-face interactions in which two people have to mutually adjust their movements in time and space are lacking. Moreover, while studies on passive observation have shown that somato-motor simulative processes are disrupted when the observed actor is perceived as an out-group or unfair individual, the impact of interpersonal perception on joint-actions has never been directly addressed. Here we explored this issue by comparing the ability of pairs of participants who did or did not undergo an interpersonal perception manipulation procedure to synchronise their reach-to-grasp movements during: i) a guided interaction, requiring pure temporal reciprocal coordination, and ii) a free interaction, requiring both time and space adjustments. Behavioural results demonstrate that while in neutral situations free and guided interactions are equally challenging for participants, a negative interpersonal relationship improves performance in guided interactions at the expense of the free interactive ones. This was paralleled at the kinematic level by the absence of movement corrections and by low movement variability in these participants, indicating that partners cooperating within a negative interpersonal bond executed the cooperative task on their own, without reciprocally adapting to the partner's motor behaviour. Crucially, participants' performance in the free interaction improved in the manipulated group during the second experimental session while partners became interdependent as suggested by higher movement variability and by the appearance of interference between the self-executed actions and those observed in the partner. Our study expands current knowledge about on-line motor interactions by showing that visuo-motor interference effects, mutual motor adjustments and motor-learning mechanisms are influenced by social perception