Oscillatory Activity in Mouse Lemur Primary Motor Cortex During Natural Locomotor Behavior

In arboreal environments, substrate orientation determines the biomechanical strategy for postural maintenance and locomotion. In this study, we investigated possible neuronal correlates of these mechanisms in an ancestral primate model, the gray mouse lemur. We conducted telemetric recordings of electrocorticographic activity in left primary motor cortex of two mouse lemurs moving on a branch-like small-diameter pole, fixed horizontally, or vertically. Analysis of cortical oscillations in high β (25–35 Hz) and low γ (35–50 Hz) bands showed stronger resting power on horizontal than vertical substrate, potentially illustrating sensorimotor processes for postural maintenance. Locomotion on horizontal substrate was associated with stronger event-related desynchronization than vertical substrate, which could relate to locomotor adjustments and/or derive from differences in baseline activity. Spectrograms of cortical activity showed modulation throughout individual locomotor cycles, with higher values in the first than second half cycle. However, substrate orientation did not significantly influence these variations. Overall, these results confirm that specific cortical mechanisms are solicited during arboreal locomotion, whereby mouse lemurs adjust cortical activity to substrate orientation during static posture and locomotion, and modulate this activity throughout locomotor cycles

Does Observation of Postural Imbalance Induce a Postural Reaction?

Import JabRef | WosArea Life Sciences and Biomedicine - Other TopicsInternational audienceBackground: Several studies bring evidence that action observation elicits contagious responses during social interactions. However automatic imitative tendencies are generally inhibited and it remains unclear in which conditions mere action observation triggers motor behaviours. In this study, we addressed the question of contagious postural responses when observing human imbalance. Methodology/Principal Findings: We recorded participants' body sway while they observed a fixation cross (control condition), an upright point-light display of a gymnast balancing on a rope, and the same point-light display presented upside down. Our results showed that, when the upright stimulus was displayed prior to the inverted one, centre of pressure area and antero-posterior path length were significantly greater in the upright condition compared to the control and upside down conditions. Conclusions/Significance: These results demonstrate a contagious postural reaction suggesting a partial inefficiency of inhibitory processes. Further, kinematic information was sufficient to trigger this reaction. The difference recorded between the upright and upside down conditions indicates that the contagion effect was dependent on the integration of gravity constraints by body kinematics. Interestingly, the postural response was sensitive to habituation, and seemed to disappear when the observer was previously shown an inverted display. The motor contagion recorded here is consistent with previous work showing vegetative output during observation of an effortful movement and could indicate that lower level control facilitates contagion effects

Perception-action coupling and postural equilibrium : basic approach. Application of observation for movement retraining in elderly subjects

L’imitation volontaire est établie comme l’un des modes principaux d’acquisition des habiletés motrices. Il existe également une autre forme d’imitation, automatique et involontaire, étudiée initialement en psychologie sociale du fait de son interaction étroite avec les comportements pro-sociaux. Récemment, et sous l’influence de travaux des années 1990 mettant en lumière des substrats neuronaux communs à l’observation et à l’exécution du mouvement, les recherches scientifiques se sont concentrées sur cette notion d’imitation automatique et ont investigué, via différents paradigmes expérimentaux, les effets de facilitation et d’interférence entre mouvements observés et exécutés. Le travail réalisé dans le cadre de cette thèse vise à améliorer notre compréhension des mécanismes de contagion motrice et à identifier leurs applications possibles au réentraînement moteur. Dans une première étude, nous avons évalué l’impact de l’observation de mouvements de déséquilibre sur le balancement postural d’observateurs jeunes (24,5 ± 5 ans), sans troubles posturaux. Le contrôle de l’équilibre orthostatique fait principalement intervenir des structures sous-corticales pour le maintien du tonus postural et l’intégration multisensorielle. Ces substrats neuronaux seraient, de la même manière que les fonctions végétatives indépendantes du contrôle volontaire, plus facilement contaminés par les mouvements observés. Cependant, l’observation d’un déséquilibre sollicite également des mécanismes de régulation posturale, qui restreignent le balancement de l’observateur et se surajoutent à des processus inhibiteurs prévenant l’imitation compulsive des mouvements observés. Par conséquent, ce paradigme expérimental nous a permis de tester les limites des effets de contagion à partir d’une situation où les processus inhibiteurs et régulateurs de la posture étaient fortement sollicités. Cette étude nous a conduits à mettre en évidence une contamination du balancement postural des sujets par le déséquilibre observé, ce qui a confirmé l’importance et la prédominance des processus d’imitation. Ce résultat soulève des questions importantes en termes d’applications au réentraînement moteur chez les patients souffrant de troubles posturaux, en particulier chez les personnes âgées qui présentent une altération de leurs fonctions de stabilisation. En effet, si l’observation d’un déséquilibre conduit à une réaction de contagion motrice, il est vraisemblable qu’elle sollicite également des fonctions inhibitrices et régulatrices permettant la stabilisation de l’observateur. La visualisation répétée d’un déséquilibre peut-elle alors conduire à une amélioration de la stabilisation chez les personnes à risque ? Pour étudier cette question, il serait nécessaire de répéter ce protocole chez le public cible - les réponses pouvant être modulées par l’âge et les aptitudes motrices des personnes. Notre seconde étude visait à évaluer l’impact du répertoire moteur sur les réactions de contagion motrice. S’il est admis que le système moteur (contraintes biomécaniques, niveau d’expertise) affecte les processus perceptifs, son effet sur les réactions d’imitation automatique a été peu étudié. Nous avons analysé les réactions posturales d’observateurs jeunes (24,2 ± 3,7 ans), sains, face à des séquences de déséquilibre antéro-postérieur et médio-latéral. Les stratégies d’équilibration posturale sont associées à des contraintes différentes selon ces deux axes, avec une symétrie médio-latérale et une asymétrie antéropostérieure – asymétrie résultant d’une position du centre de masse en avant de l’articulation de la cheville, qui induit une sollicitation accrue des muscles du plan postérieur pour la stabilisation posturale. Un impact du système moteur sur le processus de contagion serait donc susceptible de se traduire par des réactions posturales différentes dans nos deux conditions d’observation. etcVoluntary imitation is known as a major means of acquisition of motor skills. Besides, another form of imitation, automatic and involuntary, was initially more extensively studied in social psychology, perhaps because of its close interaction with prosocial behaviors. Recently, there was a renewal of interest in automatic imitation, following research works of the 1990s that highlighted common neural substrates for movement observation and execution. In this context, scientific studies started, through various experimental paradigms, to investigate facilitation and interference effects between observed and executed movements. Research work presented in this thesis aims to improve our understanding of the mechanisms involved in motor contagion and to identify their possible application to motor retraining. For this purpose, we evaluated, in our first study, the impact of observation of postural imbalance on body sway of young (24.5 ± 5 years), healthy observers. Postural control mainly relies on subcortical structures for maintaining postural tonus and ensuring multisensory integration. Similarly to vegetative functions that are independent of voluntary control, these neural substrates would be more easily contaminated by observed movements. However in response to observed imbalance, postural regulation mechanisms, superimposed to inhibitory processes that prevent compulsive imitation, restrain observers’ disequilibrium. Therefore, this experimental paradigm enabled us to test the limits of contagion mechanisms in a situation highly soliciting inhibitory and regulation processes. Our results led us to highlight a contagion effect of observed imbalance on subjects’ postural sway, which confirmed the importance of imitation processes. These results raise an important question in terms of applications for movement retraining in patients with postural disorders, more specifically in elderly patients with impaired stabilization functions. In effect, if observation of postural imbalance leads to a motor contagion response, it is also likely to solicit regulatory and inhibitory functions for observers’ postural stabilization. Thus, could repeated observation of such disequilibrium movements lead to an improvement of stabilization functions for subjects with postural deficits? To investigate this question, it will be necessary to repeat this protocol with the target population, since observers’ response is likely to vary with age and motor competences. To complete this work, we conducted a second study to assess the impact of the motor repertoire on motor contagion responses. Although it is widely accepted that the motor system (biomechanical constraints, level of expertise) affects perceptual processes, its effect on imitative responses has been little studied. We analyzed postural reactions of young (24.2 ± 3.7 years), healthy observers when presented with sequences of anteroposterior and medio-lateral imbalance. Postural equilibration strategies are associated with different constraints along these two axes, with a medio-lateral symmetry and an anteroposterior asymmetry – this latter asymmetry results from a location of the center of mass ahead of the ankle joint, which induces an increased solicitation of muscles from the posterior plane for stabilization. An impact of the motor system on the contagion process could therefore appear in the form of different postural responses in our two observation conditions. Our results indicated a greater contagion effect during observation of anteroposterior compared to medio-lateral imbalance. Postural contagion is therefore conditioned by observers’ equilibration strategy. In our third study, we considered using this contagion effect for perceptual training aimed at the maintenance and improvement of elderly subjects’ motor performances. The issue of an observational training device is especially relevant when considering people for whom physical exercise is limited due to fatigue or pain.et

Couplage perception-action et équilibre postural (approche fondamentale. Application de l'observation pour le réentrainement chez les sujets agés)

L imitation volontaire est établie comme l un des modes principaux d acquisition des habiletés motrices. Il existe également une autre forme d imitation, automatique et involontaire, étudiée initialement en psychologie sociale du fait de son interaction étroite avec les comportements pro-sociaux. Récemment, et sous l influence de travaux des années 1990 mettant en lumière des substrats neuronaux communs à l observation et à l exécution du mouvement, les recherches scientifiques se sont concentrées sur cette notion d imitation automatique et ont investigué, via différents paradigmes expérimentaux, les effets de facilitation et d interférence entre mouvements observés et exécutés. Le travail réalisé dans le cadre de cette thèse vise à améliorer notre compréhension des mécanismes de contagion motrice et à identifier leurs applications possibles au réentraînement moteur. Dans une première étude, nous avons évalué l impact de l observation de mouvements de déséquilibre sur le balancement postural d observateurs jeunes (24,5 +- 5 ans), sans troubles posturaux. Le contrôle de l équilibre orthostatique fait principalement intervenir des structures sous-corticales pour le maintien du tonus postural et l intégration multisensorielle. Ces substrats neuronaux seraient, de la même manière que les fonctions végétatives indépendantes du contrôle volontaire, plus facilement contaminés par les mouvements observés. Cependant, l observation d un déséquilibre sollicite également des mécanismes de régulation posturale, qui restreignent le balancement de l observateur et se surajoutent à des processus inhibiteurs prévenant l imitation compulsive des mouvements observés. Par conséquent, ce paradigme expérimental nous a permis de tester les limites des effets de contagion à partir d une situation où les processus inhibiteurs et régulateurs de la posture étaient fortement sollicités. Cette étude nous a conduits à mettre en évidence une contamination du balancement postural des sujets par le déséquilibre observé, ce qui a confirmé l importance et la prédominance des processus d imitation. Ce résultat soulève des questions importantes en termes d applications au réentraînement moteur chez les patients souffrant de troubles posturaux, en particulier chez les personnes âgées qui présentent une altération de leurs fonctions de stabilisation. En effet, si l observation d un déséquilibre conduit à une réaction de contagion motrice, il est vraisemblable qu elle sollicite également des fonctions inhibitrices et régulatrices permettant la stabilisation de l observateur. La visualisation répétée d un déséquilibre peut-elle alors conduire à une amélioration de la stabilisation chez les personnes à risque ? Pour étudier cette question, il serait nécessaire de répéter ce protocole chez le public cible - les réponses pouvant être modulées par l âge et les aptitudes motrices des personnes. Notre seconde étude visait à évaluer l impact du répertoire moteur sur les réactions de contagion motrice. S il est admis que le système moteur (contraintes biomécaniques, niveau d expertise) affecte les processus perceptifs, son effet sur les réactions d imitation automatique a été peu étudié. Nous avons analysé les réactions posturales d observateurs jeunes (24,2 +- 3,7 ans), sains, face à des séquences de déséquilibre antéro-postérieur et médio-latéral. Les stratégies d équilibration posturale sont associées à des contraintes différentes selon ces deux axes, avec une symétrie médio-latérale et une asymétrie antéropostérieure asymétrie résultant d une position du centre de masse en avant de l articulation de la cheville, qui induit une sollicitation accrue des muscles du plan postérieur pour la stabilisation posturale. Un impact du système moteur sur le processus de contagion serait donc susceptible de se traduire par des réactions posturales différentes dans nos deux conditions d observation. etcVoluntary imitation is known as a major means of acquisition of motor skills. Besides, another form of imitation, automatic and involuntary, was initially more extensively studied in social psychology, perhaps because of its close interaction with prosocial behaviors. Recently, there was a renewal of interest in automatic imitation, following research works of the 1990s that highlighted common neural substrates for movement observation and execution. In this context, scientific studies started, through various experimental paradigms, to investigate facilitation and interference effects between observed and executed movements. Research work presented in this thesis aims to improve our understanding of the mechanisms involved in motor contagion and to identify their possible application to motor retraining. For this purpose, we evaluated, in our first study, the impact of observation of postural imbalance on body sway of young (24.5 +- 5 years), healthy observers. Postural control mainly relies on subcortical structures for maintaining postural tonus and ensuring multisensory integration. Similarly to vegetative functions that are independent of voluntary control, these neural substrates would be more easily contaminated by observed movements. However in response to observed imbalance, postural regulation mechanisms, superimposed to inhibitory processes that prevent compulsive imitation, restrain observers disequilibrium. Therefore, this experimental paradigm enabled us to test the limits of contagion mechanisms in a situation highly soliciting inhibitory and regulation processes. Our results led us to highlight a contagion effect of observed imbalance on subjects postural sway, which confirmed the importance of imitation processes. These results raise an important question in terms of applications for movement retraining in patients with postural disorders, more specifically in elderly patients with impaired stabilization functions. In effect, if observation of postural imbalance leads to a motor contagion response, it is also likely to solicit regulatory and inhibitory functions for observers postural stabilization. Thus, could repeated observation of such disequilibrium movements lead to an improvement of stabilization functions for subjects with postural deficits? To investigate this question, it will be necessary to repeat this protocol with the target population, since observers response is likely to vary with age and motor competences. To complete this work, we conducted a second study to assess the impact of the motor repertoire on motor contagion responses. Although it is widely accepted that the motor system (biomechanical constraints, level of expertise) affects perceptual processes, its effect on imitative responses has been little studied. We analyzed postural reactions of young (24.2 +- 3.7 years), healthy observers when presented with sequences of anteroposterior and medio-lateral imbalance. Postural equilibration strategies are associated with different constraints along these two axes, with a medio-lateral symmetry and an anteroposterior asymmetry this latter asymmetry results from a location of the center of mass ahead of the ankle joint, which induces an increased solicitation of muscles from the posterior plane for stabilization. An impact of the motor system on the contagion process could therefore appear in the form of different postural responses in our two observation conditions. Our results indicated a greater contagion effect during observation of anteroposterior compared to medio-lateral imbalance. Postural contagion is therefore conditioned by observers equilibration strategy. In our third study, we considered using this contagion effect for perceptual training aimed at the maintenance and improvement of elderly subjects motor performances. The issue of an observational training device is especially relevant when considering people for whom physical exercise is limited due to fatigue or pain.etcDIJON-BU Doc.électronique (212319901) / SudocSudocFranceF

Tool-use training temporarily enhances cognitive performance in long-tailed macaques (Macaca fascicularis)

Tool use relies on numerous cognitive functions, including sustained attention and understanding of causality. In this study, we investigated the effects of tool-use training on cognitive performance in primates. Specifically, we applied the Primate Cognition Test Battery to three long-tailed macaques (Macaca fascicularis) at different stages of a training procedure that consisted of using a rake to retrieve out-of-reach food items. In addition, we evaluated a control group (n = 3) performing a grasping task, in order to account for possible effects related to a simple motor act. Our results showed that tool-use training enhances mean performance in the physical cognition domain, i.e. the understanding of spatial relations, numerosity and causality. In particular, causal cognition (evaluating noise- and shape-related causality and understanding of tool properties) showed significant improvement after training, whereas spatial cognition (evaluating spatial memory, object permanence, rotation and transposition) showed a trend to improvement. Despite these findings, none of our trained monkeys succeeded in the tool-use task of the Primate Cognition Test Battery, which involved an unfamiliar tool. Some training-related effects did not persist after a 35-day resting period, suggesting that continuous practice may be necessary, or that a longer training period before resting may be needed to better maintain cognitive performance. In contrast with the training group, the control group did not display any change in cognitive performance. This finding paves the way to further investigation into the link between tool-use behaviour and the evolution of primate cognition

''Do equilibrium constraints modulate postural reaction when viewing imbalance?''

Tia, Banty | Paizis, Christos | Mourey, France | Pozzo, ThierryInternational audience''Action observation and action execution are tightly coupled on a neurophysiological and a behavioral level, such that visually perceiving an action can contaminate simultaneous and subsequent action execution. More specifically, observing a model in postural disequilibrium was shown to induce an increase in observers' body sway. Here we reciprocally questioned the role of observers' motor system in the contagion process by comparing participants' body sway when watching displays of antero-posterior vs. lateral imbalance. Indeed, during upright standing, biomechanical constraints differ along the antero-posterior (A-P) and medio-lateral (M-L) axes; hence an impact of observers' postural constraints on the contagion response would result in different reactions to both types of stimuli. In response to the displays, we recorded greater area of center of pressure (Cop) displacement when watching forward/backward compared to left/right imbalance. In addition, after normalizing A-P and M-L CoP displacements by a control condition (fixation cross), A-P CoP path length when viewing forward imbalance tended to be higher than M-L CoP path length when viewing imbalance to the left or right. These results indicate that postural contagion is promoted when the display is compatible with observers' motor stabilization strategy which is mainly oriented along the A-P axis. In terms of clinical application, this study brings new indications for adaptation of observational training devices in rehabilitation programs. (C) 2012 Elsevier Inc. All rights reserved.'

Spectral Power in Marmoset Frontal Motor Cortex during Natural Locomotor Behavior

During primate arboreal locomotion, substrate orientation modifies body axis orientation and biomechanical contribution of fore- and hindlimbs. To characterize the role of cortical oscillations in integrating these locomotor demands, we recorded electrocorticographic activity from left dorsal premotor, primary motor, and supplementary motor cortices of three common marmosets moving across a branch-like small-diameter pole, fixed horizontally or vertically. Animals displayed behavioral adjustments to the task, namely, the horizontal condition mainly induced quadrupedal walk with pronated/neutral forelimb postures, whereas the vertical condition induced walk and bound gaits with supinated/neutral postures. Examination of cortical activity suggests that beta (16-35Hz) and gamma (75-100Hz) oscillations could reflect different processes in locomotor adjustments. During task, modulation of gamma ERS by substrate orientation (horizontal/vertical) and epoch (preparation/execution) suggests close tuning to movement dynamics and biomechanical demands. beta ERD was essentially modulated by gait (walk/bound), which could illustrate contribution to movement sequence and coordination. At rest, modulation of beta power by substrate orientation underlines its role in sensorimotor processes for postural maintenance