A trial-by-trial analysis was used to systematically examine the influence of switching visual conditions on visual feedback utilization for a manual aiming movement. In experiment one, vision was randomly manipulated from trial to trial with no more than four consecutive trials in the same visual condition. In experiment two, participants were provided with certainty of visual feedback availability prior to every trial. Results of both studies revealed that movement endpoint variability was most associated with visual feedback availability on the previous trial. Furthermore, correlation analyses comparing movement trajectory at 25, 50 and 75% with movement end (i.e. 100%) revealed that the efficiency of online corrections also depends on the availability of visual feedback on the previous trial. These results suggest that the accuracy of an aiming movement is highly dependent on processing of offline visual information from the preceding trial.
Improved understanding of deficits in children with lower-limb amputation (LLA) may lead to more targeted interventions and facilitate clinical decision-making in rehabilitation settings for this population. The findings contribute to the limited literature and provide a basis to further examine suitable clinical outcome measures to be used in children with LLA.
We aimed to determine if visual feedback use during aerial skills is more efficient at low angular head velocity (AHV; i.e., <350 deg/s) than at high AHV. Twelve experienced female acrobats performed 20 back tuck somersaults under four experimental conditions: full-vision (FV), vision at AHV below 350 deg/s (VBelow), vision at AHV above 350 deg/s (VAbove), and no-vision (NV). AHV was calculated in real time, and liquid crystal goggles were used to manipulate vision. Two gymnastics judges scored landing stability using a four-point scale. All vision conditions that allowed some vision yielded significantly better landing scores than in the NV condition. Furthermore, a nonparametric test revealed that VBelow yielded a better performance ranking than the FV condition. We conclude that visual feedback during a back tuck somersault is used for landing stability at all angular head velocities, but optimal feedback use occurs when there is retinal stability.
Previous research has demonstrated that movement time and kinematic properties of limb trajectories to the first target of a two-target reversal movement differ to that of single-target responses. In the present study we investigated whether two-target reversal movements are organized as a single unit of action or two separate components by perturbing the number of targets prior to and during movement execution. In one experiment, participants performed single-target movements and on one-third of the trials a second target was presented either at target presentation, movement onset or peak velocity. On those trials in which a second target was presented, participants were required to complete their movement to the first target and then move to the second target. In a second experiment, the reverse was the case with participants performing two-target movements that changed to single-target movement on one-third of the trials. A two-target movement time advantage was observed only when the required response was specified prior to movement initiation. Also, participants failed to prevent movement towards the second target when the requirements of the task changed from a two-target to single-target response at movement onset or later. These results indicate that two-target reversal movements were organized as a single unit of action prior to response initiation.
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