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

Aging Affects the Mental Rotation of Left and Right Hands

BACKGROUND:Normal aging significantly influences motor and cognitive performance. Little is known about age-related changes in action simulation. Here, we investigated the influence of aging on implicit motor imagery. METHODOLOGY/PRINCIPAL FINDINGS:Twenty young (mean age: 23.9+/-2.8 years) and nineteen elderly (mean age: 78.3+/-4.5 years) subjects, all right-handed, were required to determine the laterality of hands presented in various positions. To do so, they mentally rotated their hands to match them with the hand-stimuli. We showed that: (1) elderly subjects were affected in their ability to implicitly simulate movements of the upper limbs, especially those requiring the largest amplitude of displacement and/or with strong biomechanical constraints; (2) this decline was greater for movements of the non-dominant arm than of the dominant arm. CONCLUSIONS/SIGNIFICANCE:These results extend recent findings showing age-related alterations of the explicit side of motor imagery. They suggest that a general decline in action simulation occurs with normal aging, in particular for the non-dominant side of the body

Cognition motrice et vieillissement (aspects fondamentaux et cliniques)

L étude des représentations du mouvement via des paradigmes basés sur l imagination ou l observation d actions constitue un moyen unique d accéder au contenu cognitif - comme la planification ou la programmation - du mouvement, en s affranchissant des informations sensorielles et motrices liées à son exécution réelle. Dans cette thèse, nous nous sommes intéressés au vieillissement des capacités de représentation - ou de simulation mentale selon Marc Jeannerod - du mouvement. Dans la première étude, nous avons plus spécifiquement exploré l évolution avec l âge du contenu non conscient - en lien avec la programmation - de la simulation mentale. A l aide d une tâche où les sujets devaient déterminer la latéralité de mains gauches et droites présentées dans différentes orientations, nous avons montré que les personnes âgées avaient des difficultés à simuler implicitement des mouvements du membre supérieur, et ce d autant plus que ces mouvements étaient contraignants au niveau biomécanique. Nous avons également mis en évidence que les représentations des mouvements du bras non-dominant était plus affectées que celles concernant le bras dominant. Dans la deuxième étude, nous nous sommes plus particulièrement intéressés aux représentations conceptuelles du mouvement, en rapport avec la planification de l action. Les participants devaient replacer dans l ordre des images représentant les différentes actions nécessaires pour se relever du sol. Là encore, nous avons montré que les sujets âgés avaient plus de difficultés que les jeunes à simuler mentalement une séquence motrice complexe. Enfin, dans une dernière étude, nous avons exploré l impact d une pratique d observation du mouvement, complémentaire à une pratique physique, sur l apprentissage / réapprentissage du relevé du sol chez des personnes âgées à risque de chute. Le nombre de personnes capables de se relever a augmenté significativement à l issue du programme d entraînement dans le groupe ayant suivi cette approche. Cependant, cette amélioration de la performance ne s est pas révélée plus importante que dans un groupe contrôle ayant suivi un entraînement physique seul. Les deux premières études ont donc montré que les processus de simulation mentale du mouvement sont altérés avec l âge, notamment en ce qui concerne les actions complexes. Ces résultats soulignent le rôle des composantes centrales de l action dans le déclin des performances motrices associé au vieillissement. La dernière étude n a pas révélé d impact significatif d une pratique d observation complémentaire à une pratique physique, dans l acquisition d une séquence motrice complexe. La pratique mentale - basée sur l imagerie motrice ou l observation - devrait se restreindre à des mouvements relativement simples avec des populations âgées.The study of movement representations through experimental paradigms based on action imagination or action observation is interesting to access to the cognitive content - like planning and programming - of an action, without being perturbed by the sensory and motor information associated with the actual execution. In this thesis, we were interested in studying the aging of movement representations - or mental simulation of movements (Jeannerod, 2001). In the first study, we have more specifically explored the age-related changes of the non conscious content - related to action programming - of the mental simulation. By means of a task where the subjects had to judge the laterality of left and right hands presented in different orientations, we have shown that elderly people were impaired in implicitly simulating upper-limb movements, particularly movements requiring strong biomechanical constraints. We have also revealed that the movement representations of the non-dominant arm were more affected by aging than those of the dominant arm. In the second study, we were more particularly interested in the conceptual representations of the movement, those in relation with action planning. The participants had to put in order images representing the different actions necessary to perform to rise from the floor. Here too, we have shown that the elderly subjects had more difficulties than their younger counterparts in mentally simulating this complex motor sequence. Finally, in the last study, we have investigated the impact of a mental practice based on action observation, complementary to a physical practice, on the learning / relearning of the rising from the floor , in elderly people at risk of falling. The percent of people able to rise has significantly increased at the end of the training program in the group which has followed this method. However, this increase in performance was not significantly more important than in a control group which has only followed a physical training. Thus, the first two studies have shown that the processes of the mental simulation of movement are impaired with advancing age, especially when complex actions have to be simulated. These results highlight the role of the central components of action in the age-related decline of motor performances. The last study has not revealed a significant impact of an observational practice complementary to a physical practice in the acquisition of a complex motor sequence. The mental practice - based on motor imagery or observation - should be limited to relatively simple movements with elderly people.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Imagerie motrice et douleurs neuropathiques

Les douleurs neuropathiques – i.e. causée par une atteinte du système nerveux – seraient liées à des réorganisations corticales survenant notamment au niveau du cortex sensorimoteur. Depuis quelques années, diverses approches thérapeutiques basées entre autres sur la visualisation des parties du corps douloureuses et visant à renverser ces réorganisations corticales ont montré des effets antalgiques prometteurs. Dans cet article, nous rapportons plus particulièrement les résultats d’études montrant le potentiel de la pratique de l’imagerie motrice – i.e. la simulation mentale d’un mouvement sans son exécution – dans le traitement de trois formes de douleurs neuropathiques : les douleurs fantômes, le syndrome douloureux régional complexe et les douleurs consécutives à une lésion de la moelle épinière. Les mécanismes neurophysiologiques sous-tendant les effets antalgiques de l’imagerie sont discutés mais demeurent hypothétiques

Assessing motor imagery ability in younger and older adults by combining measures of vividness, controllability and timing of motor imagery

With the population aging, a large number of patients undergoing rehabilitation are older than 60 years. Also, since the use of motor imagery (MI) training in rehabilitation is becoming more popular, it is important to gain a better knowledge about the age-related changes in MI ability. The main goal of this study was to compare MI ability in younger and older adults as well as to propose a new procedure for testing this ability. Thirty healthy young subjects (mean age: 22.9±2.7 years) and 28 healthy elderly subjects (mean age: 72.4±5.5 years) participated in the experiment. They were administered three tests aimed at assessing three dimensions of MI: (1) the kinesthetic and visual imagery questionnaire (KVIQ) to assess MI vividness; (2) a finger-thumb opposition task to assess MI controllability; and (3) a chronometric task to assess the timing of MI. On average, the younger and older groups showed similar results on the KVIQ and the chronometric task, but the younger group was more accurate at the finger-thumb opposition task. Interestingly, there was a large variability in the performance within both groups, emphasizing the importance of considering each person individually regarding MI ability, whatever his age. Finally, we propose two indexes of MI ability to identify the potential of persons to engage in MI training programs. Future studies are needed to confirm the predictive value of these MI indexes and define inclusion/exclusion thresholds for their use as a screening tool in both younger and older adults

The influence of body configuration on motor imagery of walking in younger and older adults

Motor imagery (MI) refers to the mental simulation of a movement. It is used as a tool to improve motor function in several populations. In young adults, it has been repeatedly shown that MI of upper-limb movements is facilitated when one's posture is congruent with the movement to simulate. As MI training is notably used for improving locomotor-related activities in older populations, it may be questioned whether subjects' body configuration could also influence MI of walking movements and whether this influence is preserved with age. In the present study, we examined the impact of one's body position (congruent with walking: standing/incongruent with walking: sitting) on the duration of walking simulation over two distances (3m/6m), in 26 young (21 females, 5 males; mean: 23.2 ± 2.4 years) and 26 elderly (18 females, 8 males; mean: 72.7 ± 5.5 years) healthy subjects. It was found that, in both age groups, walking simulation times while standing were shorter than while sitting. Furthermore, walking simulation times in the standing position were closer to actual walking times to cover the same distances. The present findings extend to walking movements the notion that adopting a posture congruent with the movement to imagine facilitates the simulation process. They also suggest that, at least for simple walking tasks, this effect is maintained across the lifespan. The implication of our findings for optimizing MI training of locomotor-related activities is underlined

Accuracy.

<p>Mean proportions of correct responses (error bars represent standard errors) in the two groups, for hands shown in the four orientations, in back (A) and palm (B) views.</p

Motor imagery and aging

Motor imagery (MI) is the mental simulation of an action without its actual execution. It has been successfully used through mental practice--the repetition of imagined movements--to optimize motor function either in sport or rehabilitation settings. Healthy elderly individuals facing age-related impairments in motor function could also benefit from this method of training-retraining. The authors review studies that have investigated MI in physically and mentally healthy adults aged 55 years and older. First, they provide an overview of the psychophysical data on MI in the elderly, which show no changes with aging in the ability to imagine simple-usual movements but reveal some age-related alterations in the mental simulation of difficult-unusual movements. Second, they present emerging neuroimaging and neurostimulation data revealing that the sensorimotor system is engaged during MI in older adults. Finally, the authors emphasize the potential of using mental practice as a safe and easy way to help preserving/improving motor function in the elderly and provide some recommendations for future research in this direction

Characteristics of the two groups of subjects.

<p>Plus-minus values are means±SD.</p>1<p>Edimburgh inventory score.</p>2<p>Corsi block-tapping task.</p

Optimiser la récupération locomotrice par l’imagerie motrice

L’utilisation de l’imagerie motrice comme mode d’intervention complémentaire en rééducation neurologique a soulevé beaucoup d’intérêt depuis le début des années 2000. Dans l’ensemble, les travaux suggèrent que, lorsqu’elle est combinée à la pratique physique, la pratique mentale par imagerie motrice a des effets bénéfiques sur le réapprentissage moteur consécutif à une lésion cérébrale. Dans cet article, nous aborderons brièvement les bases théoriques sous-tendant l’usage de l’imagerie motrice en rééducation neurologique. Ensuite, nous verrons comment la capacité d’imagerie motrice peut être influencée par des atteintes neurologiques et aussi par le vieillissement normal. Enfin, nous ferons le point sur l’utilisation de l’imagerie motrice pour optimiser la reéducation de la mobilité et des fonctions locomotrices en réadaptation neurologique