Feedback Responses Must Disengage from Postural Control to Initiate Rapid Movements
Date
2021-09
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Abstract
The nervous system enables humans to respond to changes in the environment, and when necessary, update the course of an ongoing action. The process of initiating a new motor action when the task changes suddenly appears to carry a delay or time cost. Electrophysiological recordings suggest this time cost may arise from neural processing related to engaging in a new motor action. We know little about this time cost and when it arises following changes in task demands. Here we examine the time required to respond to a change in the goal of ongoing upper limb motor tasks. In 3 experiments, we applied visual perturbations while a total of 47 participants (22 females) maintained upper limb postural control (Experiment 1), performed reaching movements or maintained a fixed upper limb posture (Experiment 2), and transitioned from holding a fixed posture to initiating a reaching movement (Experiment 3). When applied in postural control, visual disturbances (‘cursor jumps’) required participants to disengage from holding a fixed limb position before initiating a rapid corrective response to drive the cursor back to the target. The same perturbations require a corrective response but do not impose a change in goal when the nervous system is already engaged in movement. Rapid muscle responses emerged as early as ~105 ms when responding to the visual perturbations during upper limb reaching movements compared to postural control. In some postural control conditions, the nervous system required ~270 ms to update muscle activity when responding to the same visual disturbances. The findings highlight slower corrective responses when required to disengage from maintaining a fixed limb position to initiate a corrective response. Taken together, our results emphasize a direct time cost when responding to changes in the goal of the task.
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Keywords
Upper limb, Reflexes, Goal-directed motor behaviour, Visual system, Cursor jump perturbations, Somatosensory system, Mechanical perturbations, Time cost
Citation
Yeung, N. (2021). Feedback responses must disengage from postural control to initiate rapid movements (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.