Search

The feeling of illusory movement is considered important in the study of human behavior because it is deeply related to motor consciousness. However, the neural basis underlying the illusion of movement remains to be understood. Following optimal vibratory stimulation of muscle tendon, certain subjects experience illusory movements while others do not. In the present fMRI study, we sought to uncover the neural basis of illusory movement awareness by contrasting a posteriori these two types of subjects. Examining fMRI data using leave‐one‐subject‐out general linear models and region of interest analyses, we found that a non‐limb‐specific associative network, including the opercular part of the right inferior frontal gyrus and the right inferior parietal lobule, was more active in subjects with illusions. On the other hand, levels of activation in other brain areas involved in kinaesthetic processing were rather similar between the two subsamples of subjects. These results suggest that activation of the right inferior frontoparietal areas, once passed a certain threshold, forms the basis of illusory movements. This is consistent with the global neuronal workspace hypothesis that associates conscious processing with surges of frontoparietal activity. Hum Brain Mapp 35:5166–5178, 2014. © 2014 Wiley Periodicals, Inc.

International audience; The present paper focuses on the organization of posture and movement under normal and microgravity conditions. Two reference values subserving the control of erect posture and the performance of movements are analyzed. The first is 'geometrical' in nature and corresponds to the orientation of a body segment with respect to the external world. The second reference value, which involves the mass and inertia of the body segments, is the position of the centre of mass with respect to the foot support area. The reorganization of these parameters which occurs under microgravity is discussed in the framework of a hierarchical model of posture. Suggestions are made for training procedures which could be used to prevent loss of balance from occurring in astronauts on landing after long space flights.

Resume Differentes etudes sur la mise en place de strategies sensorimotrices d'equilibre chez l'enfant sont rapportees dans cet article. Sur la base de ces resultats experimentaux et de deux principes fonctionnels (le choix d'un referentiel stable et la maitrise progressive des degres de liberte des differentes articulations du corps), Assaiante et Amblard [7]ont recemment propose un modele ontogenetique simple et heuristique de la construction des strategies d'equilibre depuis la naissance jusqu'a l'âge adulte. Ce modele propose, au cours de quatre periodes successives de l'ontogenese, l'existence d'un va-et-vient entre deux modes d'organisation temporelle du controle de l'equilibre: ascendant ou descendant, auxquels sont associes deux modes de fonctionnement des ensembles de segments corporels: en bloc ou articule. De recentes etudes ont pour but de mettre a l'epreuve le degre de generalite des strategies deja identifiees et d'etendre la validation du modele a des situations nouvelles qui impliquent un controle de l'equilibre lors des transitions entre les differentes phases du mouvement. Tout en introduisant un enrichissement des caracteristiques propres a chacune des periodes du modele, les resultats obtenus lors des etudes developpementales relatives au saut et a l'initiation de la marche sont tout a fait coherents avec les principes fonctionnels qui sont a la base du modele ontogenetique.

International audience; The authors of the present study tested the hypothesis that toddlers initiate lateral body stabilization first at the hip level in order to better control the center of gravity (CG), minimize the upper body destabilization induced by the movement of the feet, and prevent falls. Intersegmental coordination among the hip, the shoulder, and the head was investigated in toddlers during their 1st year of independent walking. The efficiency of locomotor balance control was examined in the frontal plane. An automatic optical TV image processor (ELITE system) was used in analyzing the kinematics of foot, hip, shoulder, and head rotations. For the hip, the shoulder, and the head, appropriate anchoring indices were defined so that comparisons could be made concerning the stabilization of a given body segment with respect to its external space and to the adjacent supporting anatomical segment. Cross-correlation functions were also used for extracting the temporal patterns of the body segments that occurred during locomotion and for obtaining some information about the coupling of 2 consecutive segments such as the head-shoulder and the shoulder-hip. First, hip stabilization in space appeared from the 1st week of independent walking and clearly preceded those of the shoulder and the head, suggesting an ascending progression, with age, in the ability of new walkers to control lateral balance during locomotion. Second, the hip movements occurred before the shoulder movements and the shoulder movements before the head movements, indicating that locomotor balance control is organized temporally in an ascending fashion, from the hip to the head. Third, the high values of the correlation coefficients, mainly between the head and the shoulder, were consistent with a global en bloc operation of the head-trunk unit.

GRASSO, R., C. ASSAIANTE, P. PREVOST AND A. BERTHOZ. Development of anticipatory orienting strategies during locomotor tasks in children. NEUROSCI BIOBEHAV REV 22 (4) 533–539, 1998.—Some basic problems related to the development of goal-directed locomotion in humans are reviewed here. A preliminary study is presented which was aimed at investigating the emergence of anticipatory head orienting strategies during goal-directed locomotion in children. Eight children ranging from 3.5 to 8 years had to walk along a 90° right corner trajectory to reach a goal, both in light and in darkness. The instantaneous orientation in space of the head, trunk, hips and left foot antero/posterior axes was computed by means of an ELITE four-TV camera, 100 Hz system. The results showed that predictive head orienting movements can occur also in the youngest children. The head starts to rotate toward the goal before the corner point of the trajectory is reached. In children, the head peak rotation coincides with the trajectory corner while in adults the peak is attained before. In children, the walking speed is largely decreased in darkness. The results suggest that feedforward control of goal-directed locomotion appears very early in gait development and becomes increasingly important afterwards.

International audience; The ability voluntarily to stabilize the head in space during lateral rhythmic oscillations (0.59+/-0.09 Hz) of the trunk has been investigated during microgravity (microG) and normal gravity (nG) conditions (parabolic flights). Five healthy young subjects, who gave informed consent, were examined. The movements were performed with eyes open or eyes closed, during phases of either microG or nG. The main result was that head orientation with respect to vertical may be stabilized about the roll axis under microG with, as well as without vision, despite the reduction in vestibular afferent and muscle proprioceptive inputs. Moreover, the absence of head stabilization about the yaw axis confirms that the degrees of freedom of the neck can be independently controlled, as was previously reported. These results seem to indicate that voluntary head stabilization does not depend crucially upon static vestibular afferents. Head stabilization in space may in fact be organized on the basis of either dynamic vestibular afferents or a short-term memorized postural body schema.

Two studies investigated whether typically developing children (TD) and children with autism spectrum disorders (ASD) were able to decide whether two characters were communicating or not on the basis of point-light displays. Point-lights portrayed actors engaged or not in a social interaction. In study 1, TD children (4-10 years old; n = 36) grasped social intentions from body language, with a notable improvement around 7/8. In study 2, children with ASD (6-12 years old; n = 12) could categorize the point-light displays at above-chance levels, but performed less efficiently, especially for the social interaction displays, than TD children (matched to chronological and non-verbal mental age, 6-12 years old; n = 24). An action representation deficit is discussed in relation to a social representation deficit and it is suggested that these deficits might be linked to altered maturational process of the mirror system in ASD.

The objective of this study was to investigate the updating process of internal models of action in children and young adults, through the postural and motor strategies adopted in simple tasks, namely sit-to-stand (STS) and back-to-sit (BTS). To this end, 11 healthy children from 7 to 10 years (latest stage of childhood) and 12 healthy adults participated in the experiment. The STS and BTS tasks were performed with horizontal support surface and support surface tilted 10° to the right or forward in order to investigate the immediate adaptation of the internal representations of the movement. Movement variables that included the durations of STS and BTS and the amplitudes of the trunk movement were computed. Postural characteristics were also considered during the transition from STS to BTS, including the trunk orientation and the head stabilization strategies. Despite certain similarities with adults, especially in terms of the asymmetry of the performance times for the two tasks (STS vs. BTS) and the partial movement adaptations, the children were less able than adults to adapt both postural and movement controls to the new support conditions. Thus, it appears that the updating of internal models of action is a process that matures slowly throughout ontogenesis.

Introduction Agir avec l’environnement necessite d’etre conscient de son corps. Cette conscience corporelle est basee sur le schema corporel (SC) qui correspond a la representation interne du corps en action. Le SC se construit lentement au cours de l’ontogenese, sous-tendu par une lente maturation de la proprioception. L’objectif de cette etude est d’evaluer le developpement du SC, en particulier les modifications du reseau cerebral en charge des representations du corps en action. A cette fin, nous avons utilise une approche correlationnelle cerveau-comportement. Materiel et methodes Vingt jeunes adultes (28,2 ± 4,8 ans) et vingt enfants âges de 8 a 12 ans (10,0 ± 0,9 ans) ont effectue : –une tâche d’acuite proprioceptive ; –une tâche de delestage bimanuelle, toutes deux impliquant les representations du corps en action. Un enregistrement en IRMf de repos a egalement ete realise. L’erreur et la variabilite de position, ainsi que la stabilisation de l’avant-bras ont ete mesurees, respectivement dans chacune des deux tâches comportementales. Les correlations unissant connectivite fonctionnelle (CF) et scores comportementaux ont ensuite ete evaluees. Resultats Chez l’adulte comme chez l’enfant, nous avons pu etablir une correlation negative entre la CF impliquant les regions frontales, parietales et sous-corticales et les performances comportementales dans chacune des deux tâches. Autrement dit, plus la CF est forte entre ces regions, meilleures sont la precision de position et la stabilisation de l’avant-bras. Seule l’anticipation signe une difference developpementale avec une correlation entre la CF impliquant les regions frontales et parietales inferieures. Discussion–conclusion Le reseau des representations du corps en action connaitrait deux phases de maturation : l’une precoce relative a la composante motrice qui serait deja etabli des la fin de l’enfance, et une autre plus tardive, relative a la composante frontoparietale qui presenterait une maturation au-dela de l’adolescence.

Five groups of children from 2 to 6 years of age and a group of adults were tested during stance on a treadmill moving sinusoidally at different frequencies (0.25, 0.33, and 0.50 Hz) and a constant displacement of 12 cm in anterior-posterior direction. Biomechanical data together with electromyographic responses and videoanalysis of body movements were recorded. Differential effects of treadmill frequency on the kinematic data between children and adults were observed. For slow and for fast frequencies a reduction of the oscillations from foot to head was found, being greatest in the adult subjects and smallest in the youngest children. This damping of the oscillations was due to a forward inclination of the body around the posterior turning point and its erection around the anterior turning point. With respect to the timing this represents a feedforward mechanism to compensate for the inertial forces in an economical way for the older children and the adults. In the smaller children these body movements were delayed, indicating a more passive mode of reaction to the forward-backward sway. Correspondingly the amplitudes of the electromyographic activity were largest in the groups of the youngest children for all conditions tested, especially for the leg flexor muscles. It is suggested that the greater amplitude of leg muscle activation of the children is required to compensate for the inertial forces acting at the body less economically than for the adults. Extensor load receptors are supposed to be responsible to keep the centre of gravity over the feet. The immaturity of both the function of long-latency stretch reflexes and of the extensor load receptors may play a role in the difficulties of balance control observed in small children.

On the basis of a review of the literature including the authors' own experimental studies, a model for the ontogenesis of balance control in children was developed. This qualitative ontogenetic model has to do with the equilibrium strategies built up by children in situations which are difficult but within the scope of their abilities. The model involves two functional principles. First: The stable reference frame on which the balance control is based can be either the support on which the subject is standing or the vertical gravity. When the frame of reference is the support surface, balance control is temporally organized either from the feet to the head (posture) or from the hip to the head (locomotion) (ascending organization). When the frame of reference is the vertical gravity, balance control is temporally organized from the head to the feet (descending organization). Secondly: Children gradually become able to master the various degrees of freedom which have to be controlled simultaneously during movement. For example, the head can be stabilized either on the trunk with the neck structures blocked (the en bloc mode of operation) or in space with the neck structures loose (the articulated mode). Four main periods can be said to occur during the human life span. The first extends from birth up to the acquisition of the upright stance. This period is characterized by the development of postural responses along a cephalocaudal gradient. This chronological cephalocaudal progression with age of the ability to control several body segments may correspond to a descending temporal organization of unperturbed postural control, associated with an articulated operation of the head-trunk unit. The second period takes place from the acquisition of the upright stance up to around the age of 6. During this period, our experimental results are consistent with an ascending organization of balance control, from the feet to the head in postural stance and from the hips to the head in locomotion. This ascending organization is associated with an en bloc mode of head-trunk operation, which serves to minimize the degrees of freedom. The third period begins at around the age of 7 and continues up to an upper age-limit which is as yet unknown. It is characterized by the return to an articulated mode of head—trunk operation, whereby the head stabilization necessary for the descending temporal organization of balance control is ensured. Lastly, the fourth period, which is reached during adulthood, combines the main features of the third period with a new skill involving the articulated operation of the head-trunk unit along with a selective control of the degrees of freedom at the neck level.

International audience; The aim of this study was to explore, during adolescence, alterations in the use of a sensori-motor representation as unveiled by the measurement of anticipatory postural control in a bimanual load-lifting task. We hypothesised that adolescence constitutes a period of refinement of anticipatory postural control due to on-going updates of the body schema and sensori-motor representations. The anticipatory postural control was assessed using a bimanual load-lifting paradigm in which subjects stabilise their left postural forearm, which is supporting an object, while they use their right hand to lift up the object. Kinematics and electromyographic data were recorded in two groups of adolescents (11-13 and 14-16 years of age) and a group of adults. Age and gender effects were tested. During voluntary unloading, the postural forearm stabilisation in adolescents was still different from the adult one, suggesting that further improvement of the postural forearm stabilisation must take place after the age of 16. No differences occur in the two adolescent groups. Moreover, girls presented a better stabilisation of the postural forearm than boys, indicating an earlier refinement of anticipatory postural control. The decrease of activity over postural flexors, which ensure postural stabilisation, appeared later in adolescents with respect to adults. Delayed timing adjustments and increased variability could reflect intense developmental processes underlain by an intense period of CNS maturation during adolescence. We discuss the role of brain maturation in the refinement of sensori-motor representations and the update of body schema.

International audience; IntroductionIt has been reported that AIS rely much more on ankle proprioception to control the amplitude of the balance control commands as compared to age-matched healthy adolescents. Our hypothesis was that AIS do not neglect proprioceptive information to control posture probably because of their vestibular deficits. We investigated the proprioceptive contribution to postural control in AIS which expresses spinal deformity during a crucial transitional period of ontogenesis.Methods10 adolescents with idiopathic scoliosis (AIS) with moderate spinal deformity (10° < Cobb Angle >35°) and 10 control adolescents (CA) had to maintain vertical stance while very slow oscillations in the frontal plane (below the detection threshold of the semicircular canal system) were applied to the support with the eyes open and closed. Postural orientation and segmental stabilisation were analysed at head, shoulder, trunk and pelvis levels.ResultsScoliosis did not affect vertical orientation control and segmental stabilization strategies. Vision improves postural control in both CA and AIS, which seem more dependent on visual cues than adults.ConclusionsAIS as CA were unable to control efficiently their postural orientation on the basis of the proprioceptive cues, the only sensory information available in the EC situation, whereas in the same condition healthy young adults present no difficulty to achieve the postural control. This suggests that AIS as CA transitory neglect proprioceptive information to control their posture. These results and previous studies suggest the existence of different afferent pathways for proprioceptive information subserving different parts in sensory integration of postural control. We conclude that the static proprioceptive system is not affected by the idiopathic scoliosis, while the dynamic proprioceptive system would be mainly affected.

According to the simulation theory, the internal simulation of a movement (imagined movement, IM) and its execution (actual movement, AM) are based on the same motor representations. The brain uses these representations for controlling action. The specific objective of this study was to investigate the updating process of internal models of action in adults, through massive environmental changes involved by microgravity (0G). 0G has multiple effects on motor control, including short-term adaptations with respect to the planification and performance of actions. However, the effects of 0G on internal representations of action are still largely unknown. To address this issue, thirteen subjects performed first sit-to-stand (STS) and back-to-sit (BTS) tasks, and subsequently had to imagine movement performance in these tasks. The tasks were performed under normogravity (1G) and 0G conditions. Based on durations of actual and IMs, two main results emerged from this study. In 1G, actual and IM's durations were similar. However, in 0G, AM durations were significantly longer than IM durations. Furthermore, IM durations in 0G were similar to the 1G value. These results show that although the planification and execution of action were immediately adapted to the 0G condition, the storage of afferent information was inadequate to recalibrate the predictive model. These results suggest that sudden change in gravity was not considered for updating internal models of action, and that forward model probably required more practice in order to integrate the modification of the sensorial feedback generated by the new environmental constraints.

International audience; Subjects standing heel-to-toe on either hard ground or soft support were instructed to stand upright keeping optimal balance. Lateral accelerometric measurements at head, hip and ankle levels were subjected to conjugate cross-correlations analysis in order to determine the co-ordinated movements or strategies. The results strongly suggest that there exists a hip lateral strategy which is very similar to the hip strategy previously described in fore-aft body oscillations. This lateral hip strategy was only observed when the greatest body oscillations were observed, namely on the soft supporting surface, and its descending sequence of co-ordinated movements is consistent with the idea of a top-down organization of postural control during movement or difficult stance conditions.

BackgroundUnderstanding social interactions requires the ability to accurately interpret conspecifics' actions, sometimes only on the basis of subtle body language analysis. Here we address an important issue that has not yet received much attention in social neuroscience, that of an interaction between two agents. We attempted to isolate brain responses to two individuals interacting compared to two individuals acting independently.Methodology/principal findingsWe used minimalistic point-light displays to depict the characters, as they provide the most straightforward way to isolate mechanisms used to extract information from motion per se without any interference with other visual information. Functional magnetic resonance imaging (fMRI) method was used to determine which brain regions were recruited during the observation of two interacting agents, mimicking everyday social scenes. While the mirror and mentalizing networks are rarely concurrently active, we found that both of them might be needed to catch the social intentions carried by whole-body motion.Conclusions/significanceThese findings shed light on how motor cognition contributes to social cognition when social information is embedded in whole-body motion only. Finally, the approach described here provides a valuable and original tool for investigating the brain networks responsible for social understanding, in particular in psychiatric disorders.

International audience; How sensory organization for postural control matures in children is not clear at this time. The present study examined, in children aged 7 to 11 and in adults, the postural control modifications in quiet standing when somatosensory inputs from the ankle were disturbed. Since the reweighting of sensory inputs is not mature before 10, we hypothesized that postural stability was more affected in children than in adults when somatosensory inputs were altered and that this postural instability decreased as age increased during childhood. 37 children aged 7 to 11 years and 9 adults participated in the experiments. The postural task was a semi-tandem position with the right foot in front of the left one. Postural performance was measured by means of a force platform. Two experimental conditions were presented to the participants to maintain quiet standing: With or without altered somatosensory inputs (i.e., with or without ankles vibration). Results showed that postural stability--and thus how the reweighting process of the visual/somatosensory inputs matured--increased non-monotonically between 7 years of age and adult age: There was a linear improvement of postural stability from 7 to 10, followed by a more steady behaviour between 10 and 11 and then postural stability increased to reach the adults' level of performance.

International audience; OBJECTIVES:Whispered voice is investigated from the energetic point of view. Our hypothese is that whispered voice, and mainly the forced whispers are very similar to vocal effort, for non acoustic vocal parameters, and body movements.DESIGN:Two experiments are combined. The first experiment focused on the laryngeal aspects, mainly the subglottal pressure, and also the electroglottography. The second experiment analyzed the body movements associated with loud whispered voice.RESULTS:No electroglottograhic wave was observed during the two experiments. The vocal intensity was always lower during whispered voice than during comfortable voice (p < 0.001). In experiment 1, subglottal pressure was significantly higher during forced whisper than during the other conditions (p < 0.001). In experiment 2, the amplitude of the trunk movements in the sagittal plane were greater during loud whisper than during comfortable voice (p < 0.001).CONCLUSION:Whispered voice can be close to vocal loading, especially the loud whispered voice.; Etudes expérimentales préliminaires de la voix chuchotée : pression sous-glottique et étude posturale 1 Preliminary experimental studies of whispered voice: subglottal pressure and postural aspects Résumé Objectifs : cette étude propose de décrire les aspects éner-gétiques de la voix chuchotée, en la mettant en relation avec les éléments qui caractérisent l'effort vocal. L'hypothèse de travail est qu'il existe des similitudes entre la voix chuchotée, en parti-culier la voix chuchotée forte et l'effort vocal. Méthodes : Deux expérimentations sont combinées pour répondre à l'hypothèse de travail. L'une, centrée sur le niveau laryngé, étudiait l'électroglottographie et la pression sous-glottique réelle (expérience 1) ; l'autre analysait les modifications posturales associées à la voix chuchotée (expérience 2). Résultats : dans les deux expériences, aucune onde électroglottographique n'a été mise en évidence au cours de la production de voix chucho-tée. L'intensité de la voix chuchotée était plus faible que celle de la voix parlée (p < 0.0001). Dans l'expérience 1, la pression sous-glottique était significativement supérieure en voix chuchotée forcée que dans les autres productions (p < 0.0001). Dans l'expérience 2, les mouvements du tronc dans le plan sagittal (flexion vers l'avant) étaient significativement plus importants au cours de la production de voix chuchotée qu'au cours de la voix parlée (p < 0.001). Conclusion : la voix chuchotée dite forcée présente de nombreuses similitudes avec l'effort vocal, à l'inverse de la voix chuchotée «silencieuse». Summary Objectives: Whispered voice is investigated from the energetic point of view. Our hypothese is that whispered voice, and mainly the forced whispers are very similar to vocal effort, for non acoustic vocal parameters, and body movements. Design: Two experiments are combined. The first experiment focused on the laryngeal aspects, mainly the subglottal pressure, and also the electroglottography. The second experiment analyzed the body movement associated with loud whispered voice. Results: No electroglottograhic wave was observed during the two experiments. The vocal intensity was always lower during whispered voice than during comfortable voice (p< 0.001). In experiment 1, subglottal pressure was significantly higher during forced whisper than during the other conditions (p< 0.001). The amplitude of the trunk movements in the sagittal plane were greater during loud whisper than during comfortable voice (p< 0.001). Conclusion: Whispered voice can be close to vocal loading, especially the loud whispered voice.

International audience; AIM Postural control is a fundamental component of action in which deficits have been shown to contribute to motor difficulties in children with developmental coordination disorder (DCD). The purpose of this study was to examine anticipatory postural adjustments (APAs) in children with DCD in a bimanual load-lifting task. METHOD Sixteen children with reported motor problems (two females, 14 males; mean age 9y; SD 2y) and 16 typically developing, age-matched children (six females, 10 males; mean age 9y; SD 2y) took part in the study. The task required the children to maintain a stable elbow angle, despite imposed or voluntary unloading of the forearm. APAs were assessed using electromyography and kinematics analysis. RESULTS Although children with DCD could compensate for the consequences of unloading, the results demonstrated that APAs were less efficient in children with DCD than in typically developing children. A positive and significant coefficient of regression between the flexor inhibition latency and the postural stabilization was only found in typically developing children. INTERPRETATION The impaired fine-tuning of the muscle contribution and the poor stabilization performances demonstrate poor predictive modelling in DCD.

International audience; Introduction: Postural aspects of vocal effort are unusually described in the literature whereas they are extensively managed in speech therapy. Objectives: This study aims to determine whether body movement is a side-effect of vocal effort or an integrant part of global communication effort behaviour. The answer to this question is mainly based on the correlations between the movement and the phonation.Design: This experimental study involved healthy subjects. They had to communicate to a listener during exposure to three situations where the environmental obstacles were increasing.Results: Vocal parameters such as sound pressure level, fundamental frequency, closed quotient and words duration all increased with increasing difficulty of communication (ie. increasing vocal effort). All body segments movement increased their amplitude and duration with increasing vocal effort. Vocal and kinematic characteristics were significantly correlated.Conclusion: The close correlation of movement and vocal production during vocal effort definitely excludes that the movement is a consequence of the latter. Posture and voice are coordinated in the action of communication and each body segment seems to play a different role in the vocal effort behaviour.

From one year of age, gait and balance disorders are frequent complaints in neurology. During the first year following the acquisition of independent walking, most of the gait, such as transition from digitigrade to plantigrade locomotion, parameters are well-established in children. Nevertheless, bipedal locomotion means solving a large number of balance problems. Locomotor balance needs many years to mature in the course of ontogenesis. From various gait analysis, it was possible to establish a repertoire of locomotor strategies used in typical and pathological development. The last part of this paper is devoted to the possible responses that can be proposed for gait and balance disorders occurring during childhood.

BACKGROUND: In order to test how gravitational information would affect the choice of stable reference frame used to control posture and voluntary movement, we have analysed the forearm stabilisation during sit to stand movement under microgravity condition obtained during parabolic flights. In this study, we hypothesised that in response to the transient loss of graviceptive information, the postural adaptation might involve the use of several strategies of segmental stabilisation, depending on the subject's perceptual typology (dependence--independence with respect to the visual field). More precisely, we expected a continuum of postural strategies across subjects with 1) at one extreme the maintaining of an egocentric reference frame and 2) at the other the re-activation of childhood strategies consisting in adopting an egocentric reference frame. METHODOLOGY/PRINCIPAL FINDINGS: To check this point, a forearm stabilisation task combined with a sit to stand movement was performed with eyes closed by 11 subjects during parabolic flight campaigns. Kinematic data were collected during 1-g and 0-g periods. The postural adaptation to microgravity's constraint may be described as a continuum of strategies ranging from the use of an exo- to an egocentric reference frame for segmental stabilisation. At one extremity, the subjects used systematically an exocentric frame to control each of their body segments independently, as under normogravity conditions. At the other, the segmental stabilisation strategies consist in systematically adopting an egocentric reference frame to control their forearm's stabilisation. A strong correlation between the mode of segmental stabilisation used and the perceptual typology (dependence--independence with respect to the visual field) of the subjects was reported. CONCLUSION: The results of this study show different subjects' typologies from those that use the forearm orientation in a mainly exocentric reference frame to those that use the forearm orientation in a mainly egocentric reference frame.

The purpose of this study was to investigate the role of peripheral visual cues in locomotor equilibrium as a function of age in 3- to 12-year-old children and adults. Peripheral visual restrictions (PVR), limiting frontal vision to either 30, 60 or 120 degrees, were applied to subjects walking on a narrow beam. The subjects' locomotor equilibrium performances were evaluated in terms of the locomotor speed, which constitutes a good index to the difficulty of locomotor balancing. The results showed that the influence of peripheral visual cues on locomotor equilibrium control did not vary monotonously with age. The peripheral visual contribution to dynamic balance control increased from 3 to 6 years of age, with a maximum in 6-year-old children. The peripheral visual influence on locomotor equilibrium control then disappeared suddenly in the 7-year-old children. It tended to increase again from 8–9 years of age to adulthood. In adults, the peripheral visual contribution to locomotor equilibrium that we have described previously was confirmed and compared to that involved in postural control. It is concluded from these results that late improvements occur in locomotor balance control during childhood.

Internal models are constantly updated based on the actions and experiences of a person in the world. In the present study, we proposed to assess the updating process of internal models of action by providing new environmental constraints for motor planning, postural control, and execution processes in daily tasks such as STS and BTS. STS and BTS tasks were performed with different inclinations of the support surface on which the participant and the chair were positioned: horizontal support, support tilted 10° to the right, or forward. Twelve healthy adults participated in this experiment. Kinematic characteristics were recorded using an optoelectronic motion analysis system. Movement duration and trunk inclination amplitudes were analyzed for STS and BTS as well as trunk orientation and strategies of head stabilization. Concerning the movement analysis our results showed (1) temporal asymmetry between STS and BTS, attributed mainly to the integration of the mechanical effects of gravity, and (2) a decrease of trunk movements when the support was tilted forward, attesting to an immediate adaptation process. Concerning the postural analysis our study revealed that adults adopted selective head stabilization on space strategy with respect to balance constraints. To conclude, young adults were able to immediately update their internal model of action in order to optimize motor control and vertical body orientation.

Whether the vertical body orientation depends on the initial posture and/or the type of straightening up movement is the main question raised in this paper. Another objective was to specify the compensatory role of visual input while adopting an erected posture during microgravity. The final body orientation was analysed in microgravity during parabolic flights. After either (1) straightening up movement from a crouching or (2) a sitting posture, with and without vision. The main results are the following: (1) a vertical erected final posture is correctly achieved after sit to stand movement, whereas all subjects were tilted forward after straightening up from a crouching posture and (2) vision may contribute to correct final posture. These results suggest the existence of a re-weighting of the remaining sensory information, visual information, contact cutaneous cues and proprioceptive information under microgravity condition. We can put forward the alternative hypothesis that the control of body orientation under microgravity condition may also be achieved on the basis of a postural body scheme, that seems to be dependant on the type of movement and/ or the initial position of the whole body.

International audience; The present experiment assessed, in children aged 7-11 and in adults, whether postural control is affected by cognitive processes and vice versa. Using a dual-task, the level of difficulty of a Stroop task and bipedal quiet stance varied alternatively. We hypothesised that the interference between cognitive and postural tasks was non-linear during childhood with a so-called turning point around 8. Twenty-seven children 7- to 11-years-old and nine adults participated in the experiments. The postural task was executed in a semi-tandem Romberg position. Two cognitive conditions (congruent and non-congruent Stroop conditions) and two postural situations (with and without perturbed proprioceptive inputs) were presented simultaneously with the instruction to respond as correctly as possible while remaining as stable as possible. Results showed that, in the Vib condition, CoP mean velocity decreased with the increased cognitive complexity only in children aged 7. Moreover, the data showed a non-linear decrease in postural sway during childhood, whatever the level of complexity of the cognitive and/or postural tasks. CoP mean amplitude and mean velocity decreased between 7 and 8, and again between age 11 and adults. This study (1) confirmed that the interference between mental activity and postural control can be attributed mainly to attentional limitations, (2) showed the existence of a turning point around 8 in the development of this capacity, and (3) suggested that the mature level of attentional resources was not reached until age 11. Further research is needed to assess the development of attention implied in a cognitive/postural dual-task, including probably another so-called turning point during the adolescence.

International audience; Introduction: The objective of the study was to assess how posture and vocal acoustics are modified when one needs to communicate despite environmental obstacles (i.e. vocal effort performance).Method: 20 healthy young women participated to this study. They had to communicate numbers to a listener. Environmental obstacles were the distance between the subject and the auditor, and the noise. Segmental posture modifications were recorded and analyzed using the numerical infra-red system for movement analysis SMART®. Vocal acoustics and electroglottography were also recorded and analyzed using the EVA® system.Results: The study showed the presence of objective postural modifications during vocal effort. Their amplitude increased when the environmental obstacles to communications increased, and they anticipated the vocal production.Discussion: The vocal effort concept and its relation with the posture, the voice and the subject’s feeling are reviewed on the basis of these results. Laryngeal effort is not isolated, but belongs to a global behavioral strategy which aims to improving the efficiency of the communication.; Introduction : L’objectif de l’étude était d’évaluer les modifications posturales et vocales au cours d’une tâche de communication en environnement défavorable (effort vocal).Matériels et méthodes : Cette étude expérimentale a analysé le comportement vocal et postural de 20 femmes de 20 à 43 ans indemnes de problèmes posturaux, vocaux ou auditifs. Les sujets devaient dicter des nombres à un auditeur. Les conditions défavorables à la communication étaient la distance entre le sujet et l’auditeur, et le bruit ambiant. Les modifications posturales segmentaires ont été enregistrées à l’aide du système numérique infrarouge d’analyse du mouvement SMART®. Les modifications vocales étaient évaluées par des paramètres acoustiques objectifs et par électroglottographie à l’aide de la station EVA®.Résultats : L’étude a montré l’existence de modifications posturales contemporaines de l’effort vocal. Ces modifications posturales sont d’autant plus amples que l’environnement est plus défavorable (donc que l’effort vocal est plus important), et le mouvement anticipe la production vocale.Discussion : Le concept de forçage vocal et ses relations avec la posture, la voix et le ressenti du sujet sont revus sur la base de ces résultats. L’effort laryngé n’est pas seul impliqué dans l’effort vocal, il fait partie d’une stratégie comportementale globale visant à améliorer l’efficacité de la communication.

International audience

International audience; In humans, studies of back muscle activity have mainly addressed the functioning of lumbar muscles during postural adjustments or rhythmic activity, including locomotor tasks. The present study investigated how back muscles are activated along the spine during rhythmical activities in order to gain insights into spinal neuronal organization. Electromyographic recordings of back muscles were performed at various trunk levels, and changes occurring in burst amplitudes and phase relationships were analyzed. Subjects performed several rhythmic behaviors: forward walking (FW), backward walking (BW), amble walking (where the subjects moved their arms in phase with the ipsilateral leg), walking on hands and knees (HK) and walking on hands with the knees on the edge of a treadmill (Hand). In a final task, the subjects were standing and were asked to swing (Swing) only their arms as if they were walking. It was found that axial trunk muscles are sequentially activated by a motor command running along the spinal cord (which we term "motor waves") during various types of locomotion or other rhythmic motor tasks. The bursting pattern recorded under these conditions can be classified into three categories: (1) double-burst rhythmic activity in a descending (i.e., with a rostro-caudal propagation) motor wave during FW, BW and HK conditions; (2) double-burst rhythmic activity with a stationary motor wave (i.e., occurring in a single phase along the trunk) during the 'amble' walk condition; (3) monophasic rhythmic activity with an ascending (i.e., with a caudo-rostral propagation) motor wave during the Swing and Hands conditions. Our results suggest that the networks responsible for the axial propagation of motor activity during locomotion may correspond to those observed in invertebrates or lower vertebrates, and thus may have been partly phylogenetically conserved. Such an organization could support the dynamic control of posture by ensuring fluent movement during locomotion.

International audience; The purpose of this study was to investigate the functional effects of a structural deformation, internal rotations (IR) of the lower limbs, on upper body balance strategies used during locomotion in 5-6 year-old and 7-10 year-old children. Balance control was examined in terms of rotation around the longitudinal axis in horizontal plane (yaw) and around the sagittal axis in a frontal plane (roll). Kinematics of foot, pelvis, shoulder, and head rotations were measured with an automatic optical TV image processor and used to calculate angular dispersions and segmental stabilizations. Older children with IR showed a lower gait velocity, particularly in difficult balance conditions than typically developing (TD) children. In younger children, the effect of the local biomechanical deficit remained limited to the lower limbs and did not affect upper body coordination. By contrast, in older children with IR, the development of head stabilization in space was affected. This was demonstrated by an "en bloc" instead of an articulated mode of head-trunk unit systematically adopted by the control group. As pelvic stabilization remains the main reference frame to organize balance control in older children with IR, we conclude that the structural deformity of the legs affect and possibly delay the acquisition of the head stabilization in space strategy.

The study examined, in children aged 7 and adults, the postural control when a cognitive task (modified Stroop) of varying level of difficulty is executed simultaneously. Postural difficulty also varied (with or without vibrations of the ankle joint). We hypothesized that children's performance was more affected than adults', when the difficulty of the cognitive and postural tasks increased. Results (i) demonstrated that the presence of a concurrent cognitive task affected postural sway at all ages; (ii) confirmed that the interference between mental activity and postural control can be attributed mainly to general capacity limitations and (iii) showed a degradation of the postural criteria in children but not of the cognitive ones, when the postural condition was constraining.

National audience; L'effort vocal consiste en une augmentation de l'énergie produite pour communiquer. C'est le cas notamment lorsque le locuteur doit surmonter des difficultés telles que la distance de l'auditeur, son inattention, le bruit ambiant ou bien d'autres difficultés. Dans tous les cas l'effort vocal est utilisé comme mécanisme adaptatif pour tenter d'obtenir tout de même le résultat escompté sur l'auditeur (apporter une information, modifier un comportement, etc…) en améliorant le plus possible l'intelligibilité de son message. Sur le plan laryngé cet effort repose sur l'utilisation préférentielle du mode « pressé » et la voix est souvent mais non essentiellement plus forte.

Introduction La construction du schema corporel (SC) au cours de l’ontogenese repose sur les entrees sensorielles (visuelles, proprioceptives, vestibulaires) et leurs interactions avec un repertoire moteur qui s’enrichit. Le but de cette etude etait de : – tester l’influence du couplage perception-action sur la perception de postures humaines ; – valider un nouvel outil d’evaluation de la construction du SC. Materiel et methodes Vingt adultes et 20 enfants ont effectue une tâche de discrimination visuelle de photos d’individus adoptant des postures diverses impliquant les membres superieurs et inferieurs. Les sujets devaient rapporter si les postures presentees etaient identiques ou differentes. Cette tâche a ete realisee en executant des mouvements aleatoires ou specifiques de la posture observee. Une condition controle, sans mouvement, a aussi ete realisee, ainsi que les memes tests perceptifs avec des assemblages de Lego. Resultats Le pourcentage de bonnes reponses est plus important pour les items de posture que pour les items de Lego dans les deux groupes. Un effet developpemental etait observe dans la capacite a reconnaitre les postures. Effectuer des mouvements lors de la discrimination d’item avait une incidence uniquement sur les performances des enfants. Discussion–conclusion Notre test semble specifique de la perception corporelle et se revele sensible a l’âge sur la base des temps de reaction. Augmenter les effectifs et differencier les tranches d’âge devraient nous permettre d’en faire un nouvel outil simple et efficace d’evaluation de la construction du SC chez l’enfant sain et pathologique, a partir du couplage perception-action.

International audience; This review is the result of a joint reflection carried out by researchers in the fields of robotics and automatic control on the one hand and neuroscience on the other, both trying to answer the same question: what are the functional bases of bipedal locomotion and how can they be controlled? The originality of this work is to synthesize the two approaches in order to take advantage of the knowledge concerning the adaptability and reactivity performances of humans and of the rich tools and formal concepts available in biped robotics. Indeed, we claim that the theoretical framework of robotics can enhance our understanding of human postural control by formally expressing the experimental concepts used in neuroscience. Conversely, biological knowledge of human posture and gait can inspire biped robot design and control. Therefore, both neuroscientists and roboticists should find useful information in this paper.

International audience; We investigated the consequences of a progressive damage to the muscular system on the organization of anticipatory postural adjustments (APA) in children with Duchenne muscular dystrophy (DMD). We used a bimanual load-lifting task requiring the stabilization of the forearm position despite its voluntary or imposed unloading. Eight children with DMD from 4 to 11 years of age were compared to eight typically developing (TD) children. Elbow angle and multiple surface EMGs were recorded and assessed the use of APA. The muscle weakness did not impair (1) the proprioceptive afference and the motor efference constituting the unloading reflex; and (2) the use of an anticipatory function in children with DMD. However, APA used for the forearm stabilization were less efficient in the group of children with DMD. We conclude that in DMD the muscular weakness could be a restraint to the efficiency of APA with respect to TD children.

International audience; The authors investigated the emergence of independent control of body segments in bimanual tasks involving either voluntary or involuntary trunk motion by tracking the transition from an ego- to an exocentric mode of postural control during childhood (i.e., from body-referenced orientation to externally referenced action). A paradigm combining a seated manual task and various trunk manipulations described the coordination strategies used by 24 children at different ages (2 to 9 years) and by adults. The following questions were asked: (a) When do children begin to dissociate upper limb movements from those of the trunk? (b) What segmental strategies are exhibited by each age group (2-3, 4-6, and 7-9 years, and adults)? Kinematic analyses revealed that younger children (2-6 years) used either the trunk or the support surface as reference to orient the limbs. Older children (7-9 years) began to use a gravitational reference frame similar to that of adults; they uncoupled upper limb motion from the trunk in either voluntary or imposed conditions. Young children patterned the forearm trajectory after the initiating segment (support surface or the trunk), thus reducing the degrees of freedom during the dual task. Echoing previous reports, 7-9 years of age appears to be a critical period in which children master postural control and develop an internal representation of body scheme.

International audience; This article focuses on postural anticipation and multi-joint coordination during locomotion in healthy and autistic children. Three questions were addressed. (1) Are gait parameters modified in autistic children? (2) Is equilibrium control affected in autistic children? (3) Is locomotion adjusted to the experimenter-imposed goal? Six healthy children and nine autistic children were instructed to walk to a location (a child-sized playhouse) inside the psychomotor room of the pedopsychiatric centre located approximately 5 m in front of them. A kinematic analysis of gait (ELITE system) indicates that, rather than gait parameters or balance control, the main components affected in autistic children during locomotion are the goal of the action, the orientation towards this goal and the definition of the trajectory due probably to an impairment of movement planning.

In autism, the abilities of communication are affected, associated with abnormalities of cognitive, sensorial and motor development. In a previous study based on a load-lifting task, we showed impairment of anticipation in children with autism as evidenced by kinematics and eletromyographic recordings [Neurosci. Lett. 348 (2003) 17]. In the present study, we assessed the cortical counterparts of the use of anticipatory postural adjustments in a group of control children and in a group of children with autism. The tasks required maintaining a stable forearm position despite imposed or voluntary lifting of an object placed either on the controlateral forearm or on a support. We investigated the differences between the two groups of children on the Event-Related Desynchronisation (ERD) which precedes movement onset in adults [Electroencephalogr. Clin. Neurophysiol. 46 (1979) 138]. Electroencephalogram (EEG) power evolution of a 6–8-Hz frequency band was averaged before and after imposed or voluntary movement onset. EEG reactivity of control and autistic children did not differ during the imposed unloading condition, but significant differences appeared in the voluntary unloading situations. Before lifting the object, control children showed an ERD above the left motor areas. An ERD also occurred above the right motor areas when the object was placed on their forearm. This indicates that the ERD can also translate the use of anticipatory postural adjustments. By contrast, children with autism did not show an ERD in the two voluntary situations. This suggests a central deficit of anticipation in both postural and motor control in children with autism.

International audience; This study aims at investigating how do anticipatory postural adjustments develop in children with autism, during a bimanual load-lifting task that required maintaining the stabilisation of the forearm despite imposed or voluntary unloading. Elbow angle and electromyographic were recorded on the child forearm supporting the load. The forearm stabilisation was as good in children with autism as in the control group. However, in children with autism, the latencies for both kinematics and muscular events indicated an increase of the duration of unloading. These results indicate the use of a feedback rather than a feed-forward mode of control. Impairments in both the building of internal representations and the mastering of timing parameters, could explain the deficient postural anticipation reported in children with autism.

International audience; The aim of this experiment was to test the capacity of children to develop anticipation at various stages of their growth. We studied the learning process of an artificial co-ordination by means of a procedure of double unloading in two groups of children, and a group of adults. Elbow-joint angle measurement was used to assess for the improvement of the forearm stabilization through the six learning sessions. The main results report a developmental sequence of the acquisition of anticipatory postural adjustments (APA) similar to the one established for the ontogenesis of APA. A difference in learning dynamics, but also in the final level of performance, is reported between children aged 5-6 and children aged 7-8 years. The improvement occurring at the age of 7 years probably indicates maturation of internal representations, favourable to the faster setting up of operational anticipated control.

International audience; The present study addressed the question of how do anticipatory postural adjustments (APA) develop during childhood, in the range from 4 to 8 years, during a bimanual load-lifting task. This task required maintaining the stabilisation of the forearm position despite imposed or voluntary unloading of the forearm. Elbow angle and multiple surface EMG were recorded on the child postural forearm supporting a load. During voluntary unloading, the elbow flexion of the postural forearm was calculated as a percentage of the elbow flexion measured during the imposed situation. Improvement of the forearm stabilisation was observed mainly between 4--6 and 7--8 years of age, but the oldest children did not reach the adult level of stabilisation of the postural forearm. Moreover, a clear developmental sequence in the acquisition of APA was reported: first the selection of an efficient EMG pattern underlying the forearm stabilisation, and second the mastering of timing adjustments. In fact, regression of the co-contraction pattern was observed with age, together with selection of the adult-like reciprocal pattern. Mastering of the timing adjustments of the reciprocal pattern, characterised in adults by a well-synchronised co-ordination between onset of the flexor muscle contraction of the manual arm and onset of the flexor muscle inhibition of the postural forearm, progressively improves during development. Moreover, these results suggest that the internal representation of the consequences of unloading on the forearm stabilisation, underlying anticipatory function during a bimanual co-ordination task, slowly build up during childhood.

Autorisation No.2100 : TIPA est la revue du Laboratoire Parole et Langage; International audience; In this article, we present the final report of a cooperative project that was conducted by a group of clinicians and three groups of researchers belonging to CNRS or University. The aim of this project was to test a novel unifiying hypothesis in autism : are the communicative and interactive disorders in autism correlated with a temporal processing impairment of sensory and motor events. Autistic children and adolescents were tested in three experimental tasks aimed at testing i) motion vision, ii) phonems categorial perception and iii) motor anticipation. Results indicate that performance of autistic subjects is limited comparatively to that of normal control subjects in each task, which suppose that they have difficulties in processing sensory inputs and producing motor outputs online. These difficulties could account for their communicative and interactive impairments. Neurophysiological explanations involving cerebellum are proposed to explain this temporal processing deficit. Reeducational pathways using slowed down visual motion and speech flow are also suggested.; Nous présentons dans cet article la synthèse d'un projet coopératif qui a regroupé une équipe de cliniciens hospitaliers et trois équipes de chercheurs du CNRS et de l'Université, et destiné à tester une nouvelle hypothèse unificatrice dans l'autisme. La question était de savoir si les troubles communicatifs et relationnels typiques de l'autisme sont corrélés à des troubles du traitement temporel des événements sensoriels et moteurs. Des enfants et adolescents autistes ont été testés dans trois types de tâches expérimentales visant à tester i) la vision du mouvement, ii) la perception catégorielle de phonèmes et iii) l'anticipation motrice. Les résultats montrent que dans chacun de ces trois domaines, les performances des sujets autistes sont limitées par rapport à celles des sujets témoins, et témoignent d'une difficulté à traiter les événements sensoriels et produire des événements moteurs en temps réel. Cette difficulté pourrait rendre compte des anomalies communicatives et relationnelles des sujets autistes. Des explications neurophysiologiques de ce déficit du traitement temporel impliquant notamment le cervelet sont proposées. Des voies de rééducation utilisant le ralentissement des mouvements visuels et du flux verbal sont également suggérées.

Introduction La gravite est une constante qui joue un role capital dans l’execution et la perception du mouvement humain. Sur Terre, les informations gravito-inertielles nourrissent l’ensemble des representations internes de l’action et du corps, sur lesquelles le SNC s’appuie pour controler et percevoir le mouvement. En microgravite, l’ensemble des informations graviceptives sont transitoirement supprimees ou perturbees. Afin de preciser les capacites du SNC a extraire les informations gravito-inertielles pertinentes contenues dans la cinematique d’un mouvement humain, nous avons mis au point un ensemble de stimuli enregistres en normo- et microgravite, modelises sous la forme de points lumineux. Materiel et methode Nous avons examine les reseaux cerebraux en charge de la perception visuelle du mouvement humain realise en normo- et microgravite, chez 20 jeunes adultes, naifs a la microgravite, lors d’une etude en imagerie par resonance magnetique fonctionnelle (IRMf). Resultats – discussion La perception du mouvement humain dans les deux conditions s’appuie sur un reseau cerebral identique impliquant des regions frontale, parietale et temporo-occipitale, caracteristiques de la perception des mouvements biologiques. En revanche, il existe des gradients d’activation au niveau de certaines regions motrices, qui appartiennent au systeme des neurones miroirs, en particulier le cortex moteur primaire, dont l’activation est plus importante dans la condition normogravite. Ainsi, la perception du mouvement humain, en normo comme en microgravite, s’effectue au travers d’un processus de resonance motrice dans lequel les mouvements observes sont simules par le sujet observateur sur la base de propre son repertoire moteur ; les 8-mouvements jamais executes en microgravite conduisant a une moindre activation de ses regions motrices.

Introduction Agir avec son environnement necessite d’etre conscient de son propre corps. Cette conscience corporelle est basee sur le schema corporel qui correspond a la representation interne du corps en action. La construction du schema corporel au cours de l’ontogenese repose grandement sur la proprioception. La maturation des bases cerebrales sous-jacentes a l’integration proprioceptive reste encore peu connue. C’est autour de 8 ans que l’integration d’informations proprioceptives au service du controle en ligne du mouvement devient plus operationnelle, signant une maturation progressive des afferences proprioceptives (Contreras-Vidal et al., 2006). De plus, une immaturite du reseau proprioceptif a ete observee chez les adolescents, qui se caracterise par une moindre differentiation en comparaison des adultes (Cignetti et al., 2014 ; Assaiante et al., 2014). Materiel et methode Vinght enfants de 8 a 10 ans, ont ete places dans un scanner IRMf. Des illusions de mouvement de flexion plantaire ont ete induites grâce a des vibrateurs. Les vibrations delivrees etaient soit de faible frequence (30 Hz), soit de plus haute frequence (100 Hz) pouvant provoquer une illusion de mouvement. Resultats – discussion Les analyses preliminaires des cartes d’activation et de connectivite fonctionnelle et structurelle suggerent une moindre maturite des regions fronto-parietales sous-jacentes a l’integration proprioceptive chez l’enfant, a l’inverse des regions sensorimotrices dont les proprietes sont comparables a celles de l’adulte. La construction du schema corporel, qui s’appuie sur ces regions associatives, est donc un processus qui mature lentement au cours de l’ontogenese.

78 Rythme mu et precision temporelle de l’inhibition musculaire : une longue maturation au cours de l’adolescence F. Barlaama,b,c,d,e, C. Fortina,b,c, M. Vaugoyeaua,b,c, C. Schmitzd,e, C. Assaiantea,b,c a Laboratoire de neuroscience cognitive, LNC, UMR 7291, centre national de la recherche scientifique, centre Saint-Charles, pole 3C, Case C, 3, place Victor-Hugo, 13331Marseille cedex 3, France b Aix-Marseille universite, Marseille, France c Federation de recherche N3512, comportement, cerveau, cognition, Marseille, France d Inserm U1028, CNRS UMR5292, equipe DYCOG, centre de recherche en neuroscience de Lyon, centre hospitalier Le Vinatier (Bât. 452), 95, boulevard Pinel, Bron, France e Universite Claude-Bernard Lyon 1, Lyon, France