Anticipating the terminal position of an observed action: Effect of kinematic, structural, and identity information

International audienc

Visual Perception of Elliptic movements in 7- to-11-year-old children : Influence of Motor Rules

Cette recherche porte sur la perception visuelle des mouvements humains chez l’enfant. Le but est de vérifier si le principe d’isochronie (tendance à maintenir le temps de mouvement constant quelle que soit son amplitude) que l’on observe sur le plan moteur est également présent sur le plan perceptif. On présentait sur un écran un point décrivant une trajectoire elliptique. La taille de l’ellipse variait de 2.94 à 53 cm. Des enfants âgés de 7 à 11 ans devaient ajuster selon leur préférence la vitesse (période) du mouvement. Les résultats montrent que la relation ente la période choisie et la taille de l’ellipse correspond à celle observée lors de la réalisation du mouvement (Viviani et Schneider, 1991) : dès 7 ans les ajustements perceptifs sont conformes au principe d’isochronie. Ces résultats permettent de discuter les liens motricité-perception.The aim of the present study is to analyse the visual perception of human movements in children. We evaluated whether the isochrony motor principle (that is the tendency to maintain constant the duration of movement across change of movement amplitude) is at work in a perceptive task. Children, aged 7 to 11 years, had to adjust the velocity (the period) of a dot depicting an elliptic motion. The size of the ellipse varied from 2.94 to 53 cm. Results showed that the relation between the chosen period and the size of the ellipse corresponded to that observed in motor production (Viviani & Schneider, 1991) : From 7-year-old perceptual adjustments were in agreement with the isochrony principle. The results are discussed in terms of motor-perception relationships

Altered Perceptual Sensitivity to Kinematic Invariants in Parkinson's Disease

Ample evidence exists for coupling between action and perception in neurologically healthy individuals, yet the precise nature of the internal representations shared between these domains remains unclear. One experimentally derived view is that the invariant properties and constraints characterizing movement generation are also manifested during motion perception. One prominent motor invariant is the “two-third power law,” describing the strong relation between the kinematics of motion and the geometrical features of the path followed by the hand during planar drawing movements. The two-thirds power law not only characterizes various movement generation tasks but also seems to constrain visual perception of motion. The present study aimed to assess whether motor invariants, such as the two thirds power law also constrain motion perception in patients with Parkinson's disease (PD). Patients with PD and age-matched controls were asked to observe the movement of a light spot rotating on an elliptical path and to modify its velocity until it appeared to move most uniformly. As in previous reports controls tended to choose those movements close to obeying the two-thirds power law as most uniform. Patients with PD displayed a more variable behavior, choosing on average, movements closer but not equal to a constant velocity. Our results thus demonstrate impairments in how the two-thirds power law constrains motion perception in patients with PD, where this relationship between velocity and curvature appears to be preserved but scaled down. Recent hypotheses on the role of the basal ganglia in motor timing may explain these irregularities. Alternatively, these impairments in perception of movement may reflect similar deficits in motor production

“Biological Geometry Perception”: Visual Discrimination of Eccentricity Is Related to Individual Motor Preferences

In the continuum between a stroke and a circle including all possible ellipses, some eccentricities seem more “biologically preferred” than others by the motor system, probably because they imply less demanding coordination patterns. Based on the idea that biological motion perception relies on knowledge of the laws that govern the motor system, we investigated whether motorically preferential and non-preferential eccentricities are visually discriminated differently. In contrast with previous studies that were interested in the effect of kinematic/time features of movements on their visual perception, we focused on geometric/spatial features, and therefore used a static visual display.In a dual-task paradigm, participants visually discriminated 13 static ellipses of various eccentricities while performing a finger-thumb opposition sequence with either the dominant or the non-dominant hand. Our assumption was that because the movements used to trace ellipses are strongly lateralized, a motor task performed with the dominant hand should affect the simultaneous visual discrimination more strongly. We found that visual discrimination was not affected when the motor task was performed by the non-dominant hand. Conversely, it was impaired when the motor task was performed with the dominant hand, but only for the ellipses that we defined as preferred by the motor system, based on an assessment of individual preferences during an independent graphomotor task.Visual discrimination of ellipses depends on the state of the motor neural networks controlling the dominant hand, but only when their eccentricity is “biologically preferred”. Importantly, this effect emerges on the basis of a static display, suggesting that what we call “biological geometry”, i.e., geometric features resulting from preferential movements is relevant information for the visual processing of bidimensional shapes

Développement des liens perception d’action-langage chez l’enfant

National audienc

The Added Value of Point-Light Display Observation in Total Knee Arthroplasty Rehabilitation Program: A Prospective Randomized Controlled Pilot Study

Background and Objectives: The present study aimed to assess the potential benefit of the observation of rehabilitation-related point-light display in addition to a conventional 3-week rehabilitation program, the objective being to improve functional capacity in patients having undergone total knee arthroplasty. Materials and Methods: Patients randomized in the control group had conventional rehabilitation treatment with two sessions per day 5 days a week of physical therapy (90 min), whereas patients in the experimental group had a program of conventional rehabilitation combined with a point-light display observation two times per day (5 min) and 3 days a week. Results: The patients of both groups had improved their performances by the end of the program, and the pre- and post-test improvement were superior for the experimental group over the control group concerning the total WOMAC score (p = 0.04), the functional WOMAC score (p = 0.03), and correct recognition of point-light displays (p = 0.003). Conclusions: These findings provide new insight favoring systematic point-light display observation to improve functional recovery in patients with total knee arthroplasty