Approche dynamique de l'apprentissage de coordinations posturales

The dynamical perspective on motor learning provides numerous theoretical principles which define the links of interdependency between pre-existing coordination and a new learned coordination mode. Although these principles are supposed to be general, they are principally based on bi-manual system studies and were assessed almost exclusively in this context. In this thesis, we studied the interaction between pre-existing modes and learning a new pattern in the different framework of the postural system. The ankle-hip coordination dynamics was investigated at various moments of the learning process and in two tasks of distinct nature. In the first task, the goal of the participants bore no relation with the ankle-hip coordination, which emerged spontaneously. In accordance with theoretical predictions from the dynamical perspective, we found a change from initial coordination patterns, in-phase and anti-phase, toward the learned pattern. For the second task, different modes of ankle-hip coordination were required, and constituted the goal of the task. In that case, the consequence of learning the new pattern was an improvement of every required pattern. This result presents no identifiable correspondence with the spontaneous coordination dynamics (revealed in the first task), and diverges from experimental observations obtained with bi-manual coordination. The theoretical and functional reasons underlying these divergences are discussed.L'approche dynamique de l'apprentissage moteur fournit de nombreux principes théoriques définissant les liens d'interdépendance entre les coordinations préexistantes et l'apprentissage d'un nouveau mode de coordination. Bien que ces principes se veuillent généraux, ils sont principalement basés sur l'étude du système bi-manuel et ont été évalués quasi-exclusivement dans ce contexte. Ce travail doctoral étudie l'interaction entre les modes préexistants et l'apprentissage d'un nouveau patron dans le cadre différent du système postural. A cette fin, la dynamique de coordination hanche-cheville est investiguée à différents moments du processus d'apprentissage et au regard de deux tâches de nature distincte. Pour le premier type de tâche, le but du participant est sans rapport avec la coordination hanche-cheville, celle-ci émerge alors de façon spontanée. En accord avec les prédictions théoriques de l'approche dynamique, nous observons une modification des patrons de coordination initiaux, en phase et en anti-phase, en direction du patron appris. Pour le second type de tâche, différents modes de coordination hanche-cheville sont requis, et constituent le but de la tâche. Dans ce cas, l'apprentissage du nouveau patron a pour conséquence une amélioration de l'ensemble des patrons requis. Ce résultat ne présente pas de correspondance identifiable avec la dynamique de coordination posturale spontanée (mise au jour avec le premier type de tâche), et diverge des observations expérimentales obtenues dans le cadre des coordinations bi-manuelles. Les raisons théoriques et fonctionnelles sous-tendant ces divergences sont discutées

Evaluation of heading performance with vibrotactile guidance: The benefits of information–movement coupling compared with spatial language

International audienceThis study quantified the effectiveness of tactile guidance in indicating a direction to turn to and measured its benefits compared to spatial language. The device (CAYLAR), which was composed of 8 vibrators, specified the requested direction by a vibration at the corresponding location around the waist. Twelve participants were tested in normal light and in total darkness with 3 guidance conditions: spatial language, a long tactile rhythm (1 s on/4 s off vibrations) providing a single stimulation before movement, and a short rhythm (200 ms on/200 ms off vibrations) allowing information–movement coupling during body rotation. We measured response time, heading error, and asked participants to rate task easiness, intuitiveness and perceived accuracy for each guidance mode. Accuracy was higher and participants’ ratings were more positive with the short tactile mode than with the 2 other modes. Compared to spatial language, tactile guidance, regardless of the vibration rhythm, also allowed faster responses and did not impair accuracy in the absence of vision. These findings quantitatively demonstrate that tactile guidance is particularly effective when it is reciprocally related to movement. We discuss implications of the benefits of perception–action coupling for the design of tactile navigation devices

Approche dynamique de l'apprentissage de coordinations posturales

L'approche dynamique de l'apprentissage moteur fournit de nombreux principes théoriques définissant les liens d'interdépendance entre les coordinations préexistantes et l'apprentissage d'un nouveau mode de coordination. Bien que ces principes se veuillent généraux, ils sont principalement basés sur l'étude du système bi-manuel et ont été évalués quasi-exclusivement dans ce contexte. Ce travail doctoral étudie l'interaction entre les modes préexistants et l'apprentissage d'un nouveau patron dans le cadre différent du système postural. A cette fin, la dynamique de coordination hanche-cheville est investiguée à différents moments du processus d'apprentissage et au regard de deux tâches de nature distincte. Pour le premier type de tâche, le but du participant est sans rapport avec la coordination hanche-cheville, celle-ci émerge alors de façon spontanée. En accord avec les prédictions théoriques de l'approche dynamique, nous observons une modification des patrons de coordination initiaux, en phase et en anti-phase, en direction du patron appris. Pour le second type de tâche, différents modes de coordination hanche-cheville sont requis, et constituent le but de la tâche. Dans ce cas, l'apprentissage du nouveau patron a pour conséquence une amélioration de l'ensemble des patrons requis. Ce résultat ne présente pas de correspondance identifiable avec la dynamique de coordination posturale spontanée (mise au jour avec le premier type de tâche), et diverge des observations expérimentales obtenues dans le cadre des coordinations bi-manuelles. Les raisons théoriques et fonctionnelles sous-tendant ces divergences sont discutées.The dynamical perspective on motor learning provides numerous theoretical principles which define the links of interdependency between pre-existing coordination and a new learned coordination mode. Although these principles are supposed to be general, they are principally based on bi-manual system studies and were assessed almost exclusively in this context. In this thesis, we studied the interaction between pre-existing modes and learning a new pattern in the different framework of the postural system. The ankle-hip coordination dynamics was investigated at various moments of the learning process and in two tasks of distinct nature. In the first task, the goal of the participants bore no relation with the ankle-hip coordination, which emerged spontaneously. In accordance with theoretical predictions from the dynamical perspective, we found a change from initial coordination patterns, in-phase and anti-phase, toward the learned pattern. For the second task, different modes of ankle-hip coordination were required, and constituted the goal of the task. In that case, the consequence of learning the new pattern was an improvement of every required pattern. This result presents no identifiable correspondence with the spontaneous coordination dynamics (revealed in the first task), and diverges from experimental observations obtained with bi-manual coordination. The theoretical and functional reasons underlying these divergences are discussed.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Affordance : théorie, caractérisation et perspectives pour l'ergonomie

International audienceThe affordance concept is a cornerstone of the ecological approach to perception and action. Popularized at the end of the eighties among the design community, it received a resounding welcome within the field of ergonomics, especially for human-computer interactions (HCI). We come back to this notion of affordance and address more specifically affordances characterization, which involves describing the environment in units intrinsic to the individual, that is, taken in reference to one’s body and action systems. After giving a short reminder of some founding principles and a definition of the concept, we detail classical formalization of affordance by reviewing some of the major findings from the literature on affordances. We conclude by discussing some of the perspectives the affordance concept and its formal description offer to ergonomics, well beyond the scope of HCI.Le concept d’affordance est l’un des piliers de l’approche écologique de la perception et de l’action. Popularisé à la fin des années quatre-vingt auprès de la communauté du design, il a connu un écho retentissant en ergonomie, principalement dans le domaine de la conception d’interfaces homme-machine (IHM). Nous revenons sur cette notion d’affordance et plus particulièrement sur la caractérisation des affordances, qui repose sur une description de l’environnement dans une unité intrinsèque à l’individu, c’est-à-dire en référence à son corps ou à ses systèmes d’action. Après un bref rappel de quelques principes fondateurs et une définition du concept, nous détaillons le formalisme classiquement employé pour caractériser une affordance, jusqu’à ses évolutions récentes, au travers de quelques résultats majeurs de la littérature sur les affordances. Enfin, nous discutons des perspectives qu’offrent, bien au-delà des IHM, la notion d’affordance et son formalisme en ergonomie

(De)stabilization of required and spontaneous postural dynamics with learning

International audienceThe present research examined how learning a new ankle-hip coordination influenced the preexisting postural repertoire. Standing participants learned a new ankle-hip coordination mode (relative phase of 90°). Before and after practice, postural patterns were evaluated in two different tasks. In the required task, specific ankle-hip patterns were requested (12 relative phases in multiples of 30°). In the spontaneous task, participants performed a tracking task in which no instructions about ankle-hip coordination were given. Learning induced changes in both required and spontaneous coordination dynamics. When ankle-hip patterns were required, learning led to improvement and homogenization in performance over the entire postural repertoire. When ankle-hip patterns emerged spontaneously, in-phase and anti-phase preexisting patterns destabilized and changed toward the learned pattern of 90°. These findings demonstrate that learning a new coordination pattern can induce modifications of patterns that have not been practiced. The results also suggest that the consequences of learning do not generalize across different types of tasks, even when similar coordination modes are involved. We discuss implications of these findings for the generality of learning mechanisms

Assistance vibrotactile à l'interception locomotrice de cibles mobiles : étude de faisabilité

International audiencePeut-on assister les actions locomotrices d'interception de cibles mobiles en absence de vision grâce à un dispositif de suppléance sensorielle tactile ? Lorsque la cible à intercepter est visible, une personne peut ajuster sa vitesse de déplacement de façon à annuler le taux de changement de l'angle entre sa direction de déplacement et celle de la cible (constant bearing angle, CBA). Nous présentons ici les développements technologiques et une étude de faisabilité visant à évaluer l'utilisabilité d'un dispositif de suppléance sensorielle tactile destiné à assister les actions locomotrices d'interception. Nos résultats suggèrent que moyennant une période d'apprentissage, le couplage CBA, naturellement observé lorsque la vision est disponible peut être maintenu lors de l'utilisation de notre dispositif. Nous discutons les résultats préliminaires de cette étude au regard des changements expérimentaux que nous introduirons à l'avenir dans notre programme scientifique

Assistance vibrotactile à l'interception locomotrice de cibles mobiles : étude de faisabilité

Organisateurs : Université de Genève (Germain Poizat, Raphaël Maion, Simon Flandin), Haute Ecole Spécialisée de Suisse Occidentale (Carole Baudin, Bruno Parent, Rafaël Weissbrodt), Centre universitaire de médecine générale et de santé publique (Claire Bauduin), Centre hospitalier universitaire vaudois (Vera Bustamante) Hopitaux Universitaire de Genève (Christine Villaret), Optimance (David Bozier).International audienceCan we assist the locomotor actions of intercepting moving targets in the absence of visionusing a tactile sensory augmentation system? When the target to be intercepted is visible, a person canadjust their walking speed so as to null the rate of change of the angle between their direction and thetarget (maintaining constant bearing angle, CBA). We present technological developments and afeasibility study evaluating the usability of a tactile sensory augmentation device intended to assist thelocomotor actions of interception. Our results suggest that CBA coupling, which is naturally observedwhen vision is available, can be maintained when using our device, after a training period. We discussthe preliminary results of this study in the light of the experimental changes we will introduce into ourscientific program in the future.Peut-on assister les actions locomotrices d'interception de cibles mobiles en absence de vision grâce à un dispositif de suppléance sensorielle tactile ? Lorsque la cible à intercepter est visible, une personne peut ajuster sa vitesse de déplacement de façon à annuler le taux de changement de l'angle entre sa direction de déplacement et celle de la cible (constant bearing angle, CBA). Nous présentons ici les développements technologiques et une étude de faisabilité visant à évaluer l'utilisabilité d'un dispositif de suppléance sensorielle tactile destiné à assister les actions locomotrices d'interception. Nos résultats suggèrent que moyennant une période d'apprentissage, le couplage CBA, naturellement observé lorsque la vision est disponible peut être maintenu lors de l'utilisation de notre dispositif. Nous discutons les résultats préliminaires de cette étude au regard des changements expérimentaux que nous introduirons à l'avenir dans notre programme scientifique

Spatiotemporal influences on the recognition of two-dimensional vibrotactile patterns on the abdomen

International audienceSpatial and temporal factors are known to highly influence tactile perception, but their role has been largely unexplored in the case of two-dimensional (2D) pattern recognition. We investigated whether recognition is facilitated by the spatial and/or temporal separation of pattern elements, or by conditions known to favor perceptual integration, such as the ones eliciting apparent movement. 2D vibrotactile patterns were presented to the abdomen of novice participants. In Experiment 1, we manipulated the spatial (inter-tactor distance) and temporal (burst duration and inter-burst interval) parameters applied to the tracing mode (sequential activation of pattern elements). In Experiment 2, we compared display modes differing in their level of temporal overlap in the presentation of pattern elements: the static mode (simultaneous activation of pattern elements), the slit-scan mode (pattern revealed line by line), and the tracing mode. The results of both experiments reveal that (a) recognition performance increases with the isolation of pattern elements in space and/or in time, (b) spatial and temporal factors interact in pattern recognition, and (c) conditions leading to apparent movement tend to be associated with lower recognition accuracy. These results further our understanding of tactile perception and provide guidance for the design of future vibrotactile communication systems

Motion sickness preceded by unstable displacements of the center of pressure.

We exposed standing participants to optic flow in a moving room. Motion sickness was induced by motion that simulated the amplitude and frequency of standing sway. We identified instabilities in displacements of the center of pressure among participants who became sick; these instabilities occurred before the onset of subjective motion sickness symptoms. Postural differences between Sick and Well participants were observed before exposure to the nauseogenic stimulus. During exposure to the nauseogenic stimulus, sway increased for participants who became sick but also for those who did not. However, at every point during exposure sway was greater for participants who became motion sick. The results reveal that motion sickness is preceded by instabilities in displacements of the center of pressure