The influence of advance information about target location and visual feedback on movement planning and execution.
ABSTRACT This study was designed to determine if movement planning strategies incorporating the use of visual feedback during manual aiming are specific to individual movements. Advance information about target location and visual context was manipulated using precues. Participants exhibited a shorter reaction time and a longer movement time when they were certain of the target location and that vision would be available. The longer movement time was associated with greater time after peak velocity. Under conditions of uncertainty, participants prepared for the worst-case scenario. That is, they spent more time organizing their movements and produced trajectories that would be expected from greater open-loop control. Our results are consistent with hierarchical movement planning in which knowledge of the movement goal is an essential ingredient of visual feedback utilization.
- SourceAvailable from: link.springer.com[Show abstract] [Hide abstract]
ABSTRACT: Visual regulation of upper limb movements occurs throughout the trajectory and is not confined to discrete control in the target area. Early control is based on the dynamic relationship between the limb, the target, and the environment. Despite robust outcome differences between protocols involving visual manipulations, it remains difficult to identify the kinematic events that characterize these differences. In this study, participants performed manual aiming movements with and without vision. We compared several traditional approaches to movement analysis with two new methods of quantifying online limb regulation. As expected, participants undershot the target and their movement endpoints were more variable when vision was not available. Although traditional measures such as reaction time, time after peak velocity, and the presence of discontinuities in acceleration were sensitive to the visual manipulation, measures quantifying the trial-to-trial spatial variability throughout the trajectory were the most effective in isolating the time course of online regulation.Behavior Research Methods 11/2010; 42(4):1087-95. · 2.12 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Cervical spinal lesions at C6 result in paralysis of the triceps brachii while leaving deltoid and elbow flexor function intact. We examined the spatial-temporal characteristics of goal-directed aiming movements performed by C6 tetraplegics who had undergone musculotendinous transfer surgery in which the posterior deltoid replaces the triceps as the elbow extensor. On some trials, liquid crystal goggles were used to eliminate vision of the limb and target upon movement initiation. Although tetraplegic participants achieved the same degree of movement accuracy/consistency as control participants, their movement times were longer regardless of whether the movements were made away from (elbow extension) or towards the body (elbow flexion). Longer movement times were related to lower peak velocities, and not the symmetry of the aiming profiles. The tetraplegic participants were no more dependent on visual feedback for limb regulation than control participants. Although the characteristics of the movement trajectories were surprisingly similar, in both vision conditions, tetraplegics required more real and proportional time to reduce spatial variability in the limb's trajectory for elbow extensions. Our results indicate that the sensorimotor system is adaptable and that the representations governing limb control are not muscle specific.Experimental Brain Research 09/2010; 206(1):81-91. · 2.22 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The online visual control of movement involves contributions from 2 processes: a process early in the trajectory concerned with comparisons between actual and expected sensory consequences and another process late in the trajectory that reduces the discrepancy between the position of the hand and the target. This experiment was designed to determine how early and late visual controls are impacted by the illusory characteristics of the target in a rapid reaching task. Participants performed 500 ms movements to the vertices of Müller-Lyer figures with the availability of full vision on the majority of trials. However, on a fraction of the trials, movements to the targets were performed with either early vision (first 200 ms of movement), late vision (last 200 ms of movement) or no vision. Although participants undershoot the targets under all target and visual conditions, the impact of the target configuration was greatest when vision was available during only the final portion of the movement trajectory and least when only early vision was available for limb regulation. Aiming bias under full-vision and no-vision conditions was intermediate. These findings indicate that visual context has a greater impact on late discrete limb regulation than on early dynamic control of the limb trajectory.Experimental Brain Research 06/2013; · 2.22 Impact Factor