Dynamic similarity promotes interpersonal coordination in joint-action

Human movement has been studied for decades and dynamic laws of motion that are common to all humans have been derived. Yet, every individual moves differently from everyone else (faster/slower, harder/smoother etc). We propose here an index of such variability, namely an individual motor signature (IMS) able to capture the subtle differences in the way each of us moves. We show that the IMS of a person is time-invariant and that it significantly differs from those of other individuals. This allows us to quantify the dynamic similarity, a measure of rapport between dynamics of different individuals' movements, and demonstrate that it facilitates coordination during interaction. We use our measure to confirm a key prediction of the theory of similarity that coordination between two individuals performing a joint-action task is higher if their motions share similar dynamic features. Furthermore, we use a virtual avatar driven by an interactive cognitive architecture based on feedback control theory to explore the effects of different kinematic features of the avatar motion on the coordination with human players

Unravelling socio-motor biomarkers in schizophrenia

We present novel, low-cost and non-invasive potential diagnostic biomarkers of schizophrenia. They are based on the ‘mirror-game’, a coordination task in which two partners are asked to mimic each other’s hand movements. In particular, we use the patient’s solo movement, recorded in the absence of a partner, and motion recorded during interaction with an artificial agent, a computer avatar or a humanoid robot. In order to discriminate between the patients and controls, we employ statistical learning techniques, which we apply to nonverbal synchrony and neuromotor features derived from the participants’ movement data. The proposed classifier has 93% accuracy and 100% specificity. Our results provide evidence that statistical learning techniques, nonverbal movement coordination and neuromotor characteristics could form the foundation of decision support tools aiding clinicians in cases of diagnostic uncertainty

Socio-motor improvisation : what are its impacts on motor behaviors?

Ce travail de thèse étudie l’improvisation socio-motrice, entre deux personnes. Nos capacités d’improvisation reflètent notre faculté à interagir avec autrui en adaptant nos réponses comportementales à celles de l’autre. Deux paramètres rendent compte de ces capacités : la créativité motrice, c’est-à-dire la richesse des mouvements, et la coordination interpersonnelle. Bien que fondamentaux dans le succès de nos interactions sociales, leur investigation conjointe, jamais réalisée, semble nécessaire. Le but de cette thèse était donc d’investiguer les comportements moteurs inter- et intra-personnels en situation d’improvisation. Pour cela, nous avons d’abord : (i) recueilli et défini les méthodes d’analyse de la créativité motrice et de la coordination, (ii) analysé les capacités d’improvisation et leur acquisition, (iii) mesuré l’effet de l’improvisation sur l’organisation posturale de chacun, et finalement (iv) évalué les capacités d’improvisation en présence d’un déficit d’interaction sociale (associé à la schizophrénie). Pris ensemble, nos résultats indiquent que l’improvisation socio-motrice est un bon témoin de nos interactions sociales. Nous montrons précisément que les capacités d’improvisation permettent de discriminer un individu sain d’un individu souffrant de déficit social. La coordination interpersonnelle semble jouer un rôle fondamental, aussi bien dans l’acquisition de l’improvisation que dans la stabilité posturale qui la sous-tend. Ces résultats sont discutés à travers l’approche des patrons dynamiques de coordination. Nous proposons un modèle simplifié de l’improvisation intégrant la coordination et la créativité. Nos conclusions offrent des perspectives permettant de mieux comprendre et améliorer nos interactions sociales, en présence ou non de désordres sociaux.This work investigates the socio-motor improvisation that occurs between two people. Improvisation capacities rely on our ability to interact with others by adapting our own behavioral answers to those of the other. Two parameters display these capacities: motor creativity (i.e., the richness of our movements) and interpersonal coordination. Although these two parameters are fundamental in the success of social interaction, they were never investigated jointly. This was the goal of our thesis. We aimed to explore intra- and interpersonal motor behaviors during improvisation. To do so, (i) we reviewed existing methods analyzing creativity and coordination, and proposed new ones, (ii) we measured improvisation capacities and their possible acquisition, (iii) we evaluated the influence of improvisation on postural organization of each person and (iv) we assessed the ability to improvise in presence of social deficits (associated with schizophrenia). Taken together, our results demonstrate that socio-motor improvisation is a good candidate to capture our social interactions. More precisely, we show that such capacities could discriminate healthy people from patients suffering from social deficits. Interpersonal coordination seems fundamental since it improves improvisation capacities and postural stability during social interaction. These results are discussed in the conceptual framework of the dynamical approach to movement coordination. We propose a simplified model of socio-motor improvisation including creativity and coordination. Finally, our conclusions offer new perspectives for the understanding and the improvement of social interactions, in presence or not of social disorders

Improvisation socio-motrice : quels impacts sur le comportement moteur ?

This work investigates the socio-motor improvisation that occurs between two people. Improvisation capacities rely on our ability to interact with others by adapting our own behavioral answers to those of the other. Two parameters display these capacities: motor creativity (i.e., the richness of our movements) and interpersonal coordination. Although these two parameters are fundamental in the success of social interaction, they were never investigated jointly. This was the goal of our thesis. We aimed to explore intra- and interpersonal motor behaviors during improvisation. To do so, (i) we reviewed existing methods analyzing creativity and coordination, and proposed new ones, (ii) we measured improvisation capacities and their possible acquisition, (iii) we evaluated the influence of improvisation on postural organization of each person and (iv) we assessed the ability to improvise in presence of social deficits (associated with schizophrenia). Taken together, our results demonstrate that socio-motor improvisation is a good candidate to capture our social interactions. More precisely, we show that such capacities could discriminate healthy people from patients suffering from social deficits. Interpersonal coordination seems fundamental since it improves improvisation capacities and postural stability during social interaction. These results are discussed in the conceptual framework of the dynamical approach to movement coordination. We propose a simplified model of socio-motor improvisation including creativity and coordination. Finally, our conclusions offer new perspectives for the understanding and the improvement of social interactions, in presence or not of social disorders.Ce travail de thèse étudie l’improvisation socio-motrice, entre deux personnes. Nos capacités d’improvisation reflètent notre faculté à interagir avec autrui en adaptant nos réponses comportementales à celles de l’autre. Deux paramètres rendent compte de ces capacités : la créativité motrice, c’est-à-dire la richesse des mouvements, et la coordination interpersonnelle. Bien que fondamentaux dans le succès de nos interactions sociales, leur investigation conjointe, jamais réalisée, semble nécessaire. Le but de cette thèse était donc d’investiguer les comportements moteurs inter- et intra-personnels en situation d’improvisation. Pour cela, nous avons d’abord : (i) recueilli et défini les méthodes d’analyse de la créativité motrice et de la coordination, (ii) analysé les capacités d’improvisation et leur acquisition, (iii) mesuré l’effet de l’improvisation sur l’organisation posturale de chacun, et finalement (iv) évalué les capacités d’improvisation en présence d’un déficit d’interaction sociale (associé à la schizophrénie). Pris ensemble, nos résultats indiquent que l’improvisation socio-motrice est un bon témoin de nos interactions sociales. Nous montrons précisément que les capacités d’improvisation permettent de discriminer un individu sain d’un individu souffrant de déficit social. La coordination interpersonnelle semble jouer un rôle fondamental, aussi bien dans l’acquisition de l’improvisation que dans la stabilité posturale qui la sous-tend. Ces résultats sont discutés à travers l’approche des patrons dynamiques de coordination. Nous proposons un modèle simplifié de l’improvisation intégrant la coordination et la créativité. Nos conclusions offrent des perspectives permettant de mieux comprendre et améliorer nos interactions sociales, en présence ou non de désordres sociaux

Understanding the Impact of Expertise in Joint and Solo-Improvisation

International audienceJoint-improvisation is not only an open-ended creative action that two or more people perform together in the context of an artistic performance (e.g., theatre, music or dance). Joint-improvisation also takes place in daily life activities when humans take part in collective performance such as toddlers at play or adults engaged in a conversation. In the context of this article, joint-improvisation has been looked at from a social motor coordination perspective. In the literature, the nature of the social motor coordination characteristics of joint-improvisation for either the creative aspect or daily life features of this motor performance remains unclear. Additionally, both solo-improvisation and joint-improvisation need to be studied conjointly to establish the influence of the social element of improvisation in the emergence of multi-agent motor coordination. In order to better understand those two types of improvisation, we compared three level of expertise - novice, intermediate and professional in dance improvisation to identify movement characteristics for each of the groups. Pairs of the same level were asked to improvise together. Each individual was also asked to perform an improvisation on his/her own. We found that each of the three groups present specific movement organization with movement complexity increasing with the level of expertise. Experts performed shorter movement duration in conjunction with an increase range of movement. The direct comparison of individual and paired Conditions highlighted that the joint-improvisation reduced the complexity of the movement organization and those for all three levels while maintaining the differences between the groups. This direct comparison amongst those three distinct groups provides an original insight onto the nature of movement patterns in joint-improvisation situation. Overall, it reveals the role of both individual and collective properties in the emergence of social coordination

iTUG features of 71 patients with THA (pre & 6 months post-surgery) and 52 control participants

AbstractThis database includes the biomechanical features of the fastest of three instrumented Timed Up-and-Go (iTUG) test of 71 THA patients and 52 controls. Patients performed the iTUG test before and 6 months after surgery while controls performed the test only once. Method: - Participants were equipped with 35 reflective skin markers attached over their whole body according to the Conventional Gait Model. Markers’ trajectories were measured at 100 Hz using an eight-camera optoelectronic system (MXT 40, Vicon, Oxford, UK), filtered at 6 Hz using a fourth-order Butterworth design and then occlusions were corrected using marker intercorrelations. - Participants were asked to perform the TUG test. They sat in an armchair with a seat at 47 cm off the ground, stood up, walked to a line on the ground three meters away, turned around and came back to sit in the chair. The whole task was made at a self-selected speed, and participants were allowed to use the armrests. - Instructions were as follows: “At the start signal, stand up from the chair without using the armrests, if possible, then walk towards the line in front of you, turn back at the line and come back to the chair and sit down, without using the armrests, if possible.” - The fastest of the first three tests was retained for analysis. When sitting, the participant’s back could not touch the armchair’s backrest because of the motion capture equipment. - The TUG test was divided into four phases : sit-to-stand, walking (back and forth), turn and turn-to-sit. - The beginning and end of the TUG test phases as well as the biomechanical features were identified using a custom algorithm

Asymmetries of bilateral isometric force matching with movement intention and unilateral fatigue

International audienceDuring bilateral coordination, some level of inter-hemispheric remapping (i.e., the congruency between afferent and efferent force signals from both hemispheres) is required. In this case, sensory-motor information is exchanged between the two hemispheres, but it remains unclear whether this information exchange is always equivalent or not, especially in a bilateral isometric force-matching task. We used unilateral fatigue applied to one arm in order to determine whether inter-hemispheric remapping can vary asymmetrically during a bilateral isometric matching task. Because fatigue is considered to bias the sensory-motor system, we hypothesized that if bimanual coordination is modulated solely in function of the state of the sensory-motor system (motor efferences, inter-hemispheric inhibitions, and sensory reafferences), we should not observe any asymmetric effect of fatigue with movement intention (leading vs. matching arm). However, if any other process could participate in the modulation of inter-hemispheric remapping, we should observe an interaction between movement intentions and fatigue on the force produced. We found that, when the leading arm was the non-fatigued arm, participants succeeded in reproducing the force level with their fatigued arm. By contrast, when the leading arm was fatigued, subjects over-estimated the force level produced with their non-fatigued arm. Hence, lateralized fatigue exacerbates an asymmetric behavior that seems modulated by movement intention (leading vs. matching). In other words, when unilateral fatigue is introduced in a bilateral isometric force-matching task, inter-hemispheric remapping is asymmetrical. Intensity levels of motor commands sent to both arms (directly or modulated through inter-hemispheric inhibitions) and sensory reafferences alone cannot explain these observations. Some attentional focus may be not balanced continuously between both arms but may be mainly directed toward the matching arm

Inter-Hemispheric Remapping between Arm Proprioception and Vision of the Hand is Disrupted by Single Pulse TMS on the Left Parietal Cortex

International audienceParietal cortical areas are involved in sensori-motor transformations for their respective contralateral hemifield/body. When arms of the subjects are crossed while their gaze is fixed straight ahead, vision of the hand is processed by the hemisphere ipsilateral to the arm position and proprioception of the arm by the contralateral hemisphere. It induces interhemispheric transfer and remapping. Our objective was to investigate whether a single pulse TMS applied to the left parietal cortical area would disturb interhemispheric remapping in a similar case, and would increase a simple reaction time (RT) with respect to a control single pulse TMS applied to the frontal cortical area. Two LED were superimposed and located in front of the subjects on the saggital axis. Subjects were asked to carefully fixate on these LED during each trial. The lighting of the red LED was used as a warning signal. Following the green one was illuminated after a variable delay and served as a go-signal. The hand for the response was determined before the start of each trial. TMS was applied to the left parietal, the left frontal cortical areas, or not applied to the subject. Results revealed that: (1) Irrespective of its location, single pulse TMS induced a non-specific effect similar to a startle reflex and reduced RT substantially (15 ms on average) with respect to a control condition without TMS (mean value = 153 ms). (2) Irrespective of TMS, RT were shorter when the right or the left hand was positioned in the right visual hemi-field (i.e. normal and crossed positions respectively). (3) Finally, RT increased when single pulse TMS was applied to the left parietal area and when hands were crossed irrespective of which hand was used. We concluded that interhemispheric sensori-motor remapping was disrupted by a single pulse TMS that was applied to the left parietal cortex. This effect was also combined some visual attention directed towards the hand located on the right visual hemi-field

Age-related adaptations of lower limb intersegmental coordination during walking

Lower-limb intersegmental coordination is a complex component of human walking. Aging may result in impairments of motor control and coordination contributing to the decline in mobility inducing loss of autonomy. Investigating intersegmental coordination could therefore provide insights into age-related changes in neuromuscular control of gait. However, it is unknown whether the age-related declines in gait performance relates to intersegmental coordination. The aim of this study was to evaluate the impact of aging on the coordination of lower limb kinematics and kinetics during walking at a conformable speed. We then assessed the body kinematics and kinetics from gait analyses of 84 volunteers from 25 to 85 years old when walking was performed at their self-selected speeds. Principal Component Analysis (PCA) was used to assess lower-limb intersegmental coordination and to evaluate the planar covariation of the Shank-Thigh and Foot-Shank segments. Ankle and knee stiffness were also estimated. Age-related effects on planar covariation parameters was evaluated using multiple linear regressions (i.e., without a priori age group determination) adjusted to normalized self-selected gait velocity. Colinearity between parameters was assessed using a variation inflation factor (VIF) and those with a VIF \u3c 5 were entered in the analysis. Normalized gait velocity significantly decreased with aging (r = −0.24; P = 0.028). Planar covariation of inter-segmental coordination was consistent across age (99.3 ± 0.24% of explained variance of PCA). Significant relationships were found between age and intersegmental foot-shank coordination, range of motion of the ankle, maximal power of the knee, and the ankle. Lower-limb coordination was modified with age, particularly the coordination between foot, and shank. Such modifications may influence the ankle motion and thus, ankle power. This observation may explain the decrease in the ankle plantar flexor strength mainly reported in the literature. We therefore hypothesize that this modification of coordination constitutes a neuromuscular adaptation of gait control accompanying a loss of ankle strength and amplitude by increasing the knee power in order to maintain gait efficiency. We propose that foot-shank coordination might represent a valid outcome measure to estimate the efficacy of rehabilitative strategies and to evaluate their efficiency in restoring lower-limb synergies during walking

Standing or swaying to the beat: Discrete auditory rhythms entrain stance and promote postural coordination stability

International audienceHumans seem to take social and behavioral advantages of entraining themselves with discrete auditory rhythms (e.g., dancing, communicating). We investigated the benefits of such an entrainment on posture during standing (spontaneous entrainment) and during a whole-body swaying task (intentional synchronization). We first evaluated how body sway was entrained by different auditory metronome frequencies (0.25, 0.5, and 1.0Hz). We then assessed the stabilizing role of auditory rhythms on postural control, characterized in a dynamical systems perspective by informational anchoring of the head (local stabilization) and fewer transitions from in-phase to anti-phase ankle-hip coordination (global stabilization). Our results revealed in both situations an entrainment of postural movements by external rhythms. This entrainment tended to be more effective when the metronome frequency (0.25Hz) was close to the dominant sway frequency. Particularly, we found during intentional synchronization that head movements were less variable when paced by a slower beat (informational anchoring), and that phase transitions between the two stable patterns in postural dynamics were delayed. Our findings demonstrate that human bipedal posture can be actively or spontaneously modulated by an external discrete auditory rhythm, which might be exploited for the purpose of learning and rehabilitation