Early Impulse Control: Treatment of Potential Errors within Pre-Programming and Control

Abstract

Early aiming adjustments following an online perturbation are made possible by impulse control. This process may unfold even earlier when perturbations impose a greater risk of a costly overshoot error. Participants executed upward and downward aims to mediate the cost of potential errors—downward overshoots require more energy to correct against gravity. On 33% of the trials, texture elements on the aiming surface were shifted following onset to appear congruent or incongruent with the aiming direction, and consequently generate a misperception of the limb moving slower or faster, respectively. Thus, the risk of potential errors could be influenced by the online perturbation (e.g., increased perceived likelihood of overshooting following the incongruent background). Findings indicated greater undershooting for down compared to up, which reflects the principle of movement optimisation. There was also more undershooting for an incongruent compared to congruent background, which is consistent with early online adjustments counter-acting the misperceived limb velocity. However, there were no interactions throughout the movement trajectory. We suggest that while the initial pre-programme considers the cost of potential errors (target direction), early impulse control fails to discriminate the likelihood of these errors occurring following an online perturbation (moving background).

Keywords:

• Aiming
• impulse control
• online perturbation
• optimisation

Disclosure Statement

No potential conflict of interest was reported by the authors.

Notes

1 The appearance of early onset adjustments have been known to vary as a function of magnitude, time and/or displacement of kinematic landmarks (e.g., magnitude of peak acceleration; Grierson & Elliott, 2009b; displacement at peak velocity; Grierson & Elliott, 2008). Thus, early onset adjustments are not defined by a select dependent variable at a precise landmark, but broadly identified before the end of the primary movement (i.e., preceding the potential secondary submovement). In addition, the combination of these kinematic measures captures the potential complementarity within the trajectory itself (e.g., earlier time to peak deceleration following high-magnitude peak acceleration; Roberts et al., 2016). Thus, these kinematic measures render a potentially more complete assessment of trajectory control.

2 The same number of leftward and rightward translating background directions were incorporated into the trial procedure. However, these trials were not featured within the present design as they pertain to a separate set of analyses and related research question, which are to be addressed within a separate study.