Browsing by Author "Yeung, Natalie"
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- ItemOpen AccessFeedback Responses Must Disengage from Postural Control to Initiate Rapid Movements(2021-09) Yeung, Natalie; Cluff, Tyler; Peters, Ryan; Herzog, Walter; Dukelow, SeanThe 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.