Visual Online Control of Goal-Directed Aiming Movements in Children.

The present study investigated whether the initial impulse of goal-directed movements was visually monitored by 5- to 12-years-old children (n = 36) in a manner similar to adults (n = 12). The participants moved a cursor toward a fixed target. In some trials, the cursor was unpredictably translated by 20 mm following movement initiation.

Visual monitoring of goal-directed aiming movements.

Goal-directed movements are subject to intrinsic planning and execution variability, which requires that the central nervous system closely monitor our movements to ensure endpoint accuracy. In the present study, we sought to determine how closely the visual system monitored goal-directed aiming movements. We used a cursor-jump paradigm in which a cursor was unexpectedly translated soon after movement initiation.

The specificity of practice hypothesis in goal-directed movements: visual dominance or proprioception neglect?

The study aimed to examine whether modifying the proprioceptive feedback usually associated with a specific movement would decrease the dominance of visual feedback and/or decrease, which appears to be the neglect of proprioceptive feedback in ensuring the accuracy of goal-directed movements. We used a leg positioning recall task and measured the recall error after 15 and 165 acquisition trials performed with both vision and proprioception or proprioception only, under either a normal or a modified proprioception condition (i.e.

Observational Learning: Tell Beginners What They Are about to Watch and They Will Learn Better.

Observation aids motor skill learning. When multiple models or different levels of performance are observed, does learning improve when the observer is informed of the performance quality prior to each observation trial or after each trial? We used a knock-down barrier task and asked participants to learn a new relative timing pattern that differed from that naturally emerging from the task constraints (Blandin et al., 1999).

Prism adaptation in virtual and natural contexts: Evidence for a flexible adaptive process.

Prism exposure when aiming at a visual target in a virtual condition (e.g., when the hand is represented by a video representation) produces no or only small adaptations (after-effects), whereas prism exposure in a natural condition produces large after-effects.

Mixed observation favors motor learning through better estimation of the model's performance.

Observation contributes to motor learning. It was recently demonstrated that the observation of both a novice and an expert model (mixed observation) resulted in better learning of a complex spatio-temporal task than the observation of either a novice or an expert model alone. In the present study, we sought to determine whether the advantage of mixed observation resulted from the development of a better error detection mechanism.

Is visual-based, online control of manual-aiming movements disturbed when adapting to new movement dynamics?

Previous research has shown that for goal-directed movements, online visual feedback is not necessary for the adaptation of movement planning to novel movement dynamics. In the present study, we wanted to put this proposition to a stringent test and determine whether the usually dominant role of online visual feedback in movement control is diminished when goal-directed movements are performed in a condition that modifies limb dynamics. Participants performed a video-aiming task while the center of mass of their forearm was experimentally displaced by a 1.

Observation learning of a motor task: who and when?

Observation contributes to motor learning. It was recently demonstrated that the observation of both a novice and an expert model (mixed observation) resulted in better learning of a complex spatiotemporal task than the observation of either a novice or an expert model. In experiment 1, we aimed to determine whether mixed observation better promotes learning due to the information that can be gained from two models who exhibit different skill levels or simply because multiple models, regardless of their level of expertise, better promote learning than would a single model.

Learning through observation: a combination of expert and novice models favors learning.

Observation of an expert or novice model promotes the learning of a motor skill. In two experiments, we determined the effects of a mixed observation schedule (a combination of expert and novice models) on the learning of a sequential timing task. In Experiment 1, participants observed a novice, expert, or both novice and expert models.

Effects of the model's handedness and observer's viewpoint on observational learning.

Observation promotes motor skill learning. However, little is known about the type of model and conditions of observation that can optimize learning. In this study, we investigated the effects of the model's handedness and the observer's viewpoint on the learning of a complex spatiotemporal task.

Success modulates consolidation of a visuomotor adaptation task.

Consolidation is a time-dependent process that is responsible for the storage of information in long-term memory. As such, it plays a crucial role in motor learning. Prior research suggests that some consolidation processes are triggered only when the learner experiences some success during practice.

Congruent visual and proprioceptive information results in a better encoding of initial hand position.

Goal-directed movements performed in a virtual environment pose serious challenges to the central nervous system because the visual and proprioceptive representations of one's hand position are not perfectly congruent. The aim of the present study was to determine whether the vision of one's hand or upper arm, compared with that of a cursor representing the tips of one's index finger and thumb, optimizes the planning and modulation of one's movement as the cursor nears the target. The participants performed manual aiming movements that differed by the source of static visual information available during movement planning and the source of dynamic information available during movement execution.

Observation learning versus physical practice leads to different consolidation outcomes in a movement timing task.

Motor learning is a process that extends beyond training sessions. Specifically, physical practice triggers a series of physiological changes in the CNS that are regrouped under the term "consolidation" (Stickgold and Walker 2007). These changes can result in between-session improvement or performance stabilization (Walker 2005).

Automaticity of online control processes in manual aiming.

Experiments that manipulated the visual feedback of the moving limb have suggested the existence of efficient and automatic online correction processes. We wanted to determine whether the latency/gain of the correction for a cursor jump are only influenced by the size of the cursor jump or whether they are also influenced by the need of a correction for the target to be reached. In Experiment 1, we used two target sizes (5 and 30 mm) and three cursor-jump amplitudes (5, 15, and 25 mm), so that for some target size/cursor-jump combinations, no correction would be needed to reach the target.

Suboptimal online control of aiming movements in virtual contexts.

We determined whether uncertainty about the location of one's hand in virtual environments limits the efficacy of online control processes. In the Non-aligned and Aligned conditions, the participant's hand was represented by a cursor on a vertical or horizontal display, respectively. In the Natural condition, participants saw their hand.

Automatic movement error detection and correction processes in reaching movements.

Manual aiming movements can be amended during their execution. Recent evidence suggests that error detection and correction are based on automatic and even reflexive processing of afferent information. In this study, we wanted to determine whether these processes are affected by the occurrence of successive events requiring adjustments of the originally planned movement.

Developmental aspects of pluriarticular movement control.

Precise pluriarticular movement control is required to perform straight and smooth out-and-back movements. Our goal was to determine whether children perform out-and-back movements as accurately as adults do in the presence and absence of visual feedback. To reach our goal, 36 children aged between 6 and 12 years, and 12 young adults, performed an out-and-back movement in a normal-vision condition and in a target-only condition.

Distinct consolidation outcomes in a visuomotor adaptation task: Off-line leaning and persistent after-effect.

Consolidation is a time-dependent process responsible for the storage of information in long-term memory. As such, it plays a crucial role in motor learning. In two experiments, we sought to determine whether one's performance influences the outcome of the consolidation process.

Evidence for continuous processing of visual information in a manual video-aiming task.

Research shows that individuals are able to correct for an experimentally-induced and unexpected aiming error (i.e., a cursor jump), even when they do not detect it consciously.

Factors influencing online control of video-aiming movements performed without vision of the cursor.

A modulation of the primary impulse of manual/video-aiming movements performed without visual feedback has been reported. In the present study, we show that this modulation is modified (a) with increased practice, (b) the use of an aligned visual display, and (c) the availability of visual feedback on alternated trials. However, this modulation was not as efficient as that observed in a normal vision condition, which underlines the primary role of vision to ensure endpoint accuracy.

Modulation of the primary impulse of spatially-constrained video-aiming movements.

It has been suggested that temporally-constrained goal directed movements are based on a single submovement control strategy that could be modulated online. On the contrary, spatially-constrained movements might encourage participants to produce very fast, open-loop, but somewhat inaccurate/variable primary movement impulses and, if necessary, to perform a discrete correction. We wanted to determine whether the primary impulse of a spatially-constrained manual aiming movement was modulated online.

Straight ahead acts as a reference for visuomotor adaptation.

One can adapt movement planning to compensate for a mismatch between vision and action. Previous research with prismatic lenses has shown this adaptation to be accompanied with a shift in the evaluation of one's body midline, suggesting an important role of this reference for successful adaptation. This interpretation leads to the prediction that rotation adaptation could be more difficult to learn for some directions than others.

Specificity of practice results from differences in movement planning strategies.

Withdrawing visual feedback after practice of a manual aiming task results in a severe decrease in aiming accuracy. This decrease in accuracy is such that participants are often less accurate than controls who are beginning practice of the task without visual feedback. These results have been interpreted as evidence that motor learning is specific to the sources of afferent information optimizing performance, because it could be processed at the exclusion of other sources of afferent information.

Specificity of learning in a video-aiming task: modifying the salience of dynamic visual cues.

The authors investigated whether the salience of dynamic visual information in a video-aiming task mediates the specificity of practice. Thirty participants practiced video-aiming movements in a full-vision, a weak-vision, or a target-only condition before being transferred to the target-only condition without knowledge of results. The full- and weak-vision conditions resulted in less endpoint bias and variability in acquisition than did the target-only condition.

Movement planning of video and of manual aiming movements.

We studied aiming performance of adults for video- and manual aiming tasks when they had visual information about the location of the starting base or when they had not. In video-aiming, foveating the starting base and then the target prior to movement initiation (Foveation) resulted in less aiming bias and variability than when the starting base was not visible (PNV), or visible without the participants foveating it prior to movement initiation (PSV). In manual aiming, Foveation and PSV procedures resulted in identical results but reduced aiming bias and variability in comparison to the PNV procedures.