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: Florian Van Halewyck[Show abstract] [Hide abstract]
ABSTRACT: Age has a clear impact on one's ability to make accurate goal-directed aiming movements. Older adults seem to plan slower and shorter-ranged initial pulses towards the target, and rely more on sensory feedback to ensure endpoint accuracy. Despite the fact that these age-related changes in manual aiming have been observed consistently, the underlying mechanism remains speculative. In an attempt to isolate four commonly suggested underlying factors, young and older adults were instructed to make discrete aiming movements under varying speed and accuracy constraints. Results showed that older adults were physically able to produce fast primary submovements and that they demonstrated similar movement-programming capacities as young adults. On the other hand, considerable evidence was found supporting a decreased visual feedback-processing efficiency and the implementation of a play-it-safe strategy in older age. In conclusion, a combination of the latter two factors seems to underlie the age-related changes in manual aiming behaviour.Experimental Brain Research 03/2015; DOI:10.1007/s00221-015-4247-3 · 2.17 Impact Factor
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ABSTRACT: Goal-directed aiming movements are planned and executed so that they optimize speed, accuracy and energy expenditure. In particular, the primary submovements involved in manual aiming attempts typically undershoot targets in order to avoid costly time and energy overshoot errors. Furthermore, in aiming movements performed over a series of trials, the movement planning process considers the sensory information associated with the most recent aiming attempt. The goal of the current study was to gain further insight into how the sensory consequences associated with the recent and forthcoming aiming attempts impact performance. We first examined whether performers are more conservative in their aiming movements with a heavy, as opposed to a light, stylus by determining whether primary submovements undershot the target to a greater extent in the former due to an anticipated increase in spatial variability. Our results show that movements with the heavy stylus demonstrated greater undershoot biases in the primary submovements, as well as greater trial-to-trial spatial variability at specific trajectory kinematic landmarks. In addition, we also sought to determine whether the sensory information experienced on a previous aiming movement affected movement planning and/or online control on the subsequent aiming attempt. To vary the type sensory consequences experienced on a trial-to-trial basis, participants performed aiming movements with light and heavy styli in either blocked or random orderings of trials. In the random-order conditions, some participants were provided advance information about stylus mass for the upcoming trial, while others were not. The blocked and random trial orders had minimal impacts on end point aiming performance. Furthermore, similarities in the times to key kinematic landmarks in the trajectories of the random-order groups suggest that recent trial experience had a greater effect on the upcoming aiming movement compared with advance task knowledge.Experimental Brain Research 01/2015; DOI:10.1007/s00221-014-4191-7 · 2.17 Impact Factor
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ABSTRACT: Adam, Mol, Pratt, and Fischer (2006) reported what they termed ''a violation of Fitts's Law'' – when participants aimed to targets in an array, movement times (MTs) to the last target location (highest index of difficulty (ID)) were shorter than predicted by Fitts's Law. Based on the results of subsequent studies in which place-holders were present either during planning and/or execution stages of the movements, it was suggested that the violation may emerge because of context-dependent changes in planning pro-cesses. The present study examined this planning explanation by conducting detailed kinematic analyses of movements. Partici-pants performed aiming movements to sets of 3 targets in different placeholder arrays with different movement amplitudes. Consis-tent with previous Fitts's Law violation findings, MTs were not sig-nificantly longer for movements to the last versus middle target location. Interestingly, the pattern of peak limb velocities (typically associated with planning processes) did not mirror the changes in MTs. On the other hand, analyses of the effector's spatial variability during the movement suggested greater involvement of online control processes when the target was in the last position. Based on these results, we suggest that the Fitts’ Law violation observed here occurred because of more efficient online control processes.Human Movement Science 02/2015; 39:163-176. DOI:10.1016/j.humov.2014.11.005 · 2.03 Impact Factor