Failed stopping transiently suppresses the electromyogram in task-irrelevant muscles.

Abstract

Selectively stopping individual parts of planned or ongoing movements is an everyday motor skill. For example, while walking in public you may stop yourself from waving at a stranger who you mistook for a friend while continuing to walk. Despite its ubiquity, our ability to selectively stop actions is limited. Canceling one action can delay the execution of other simultaneous actions. This stopping-interference effect on continuing actions during selective stopping may be attributed to a global inhibitory mechanism with widespread effects on the motor system. Previous studies have characterized a transient global reduction in corticomotor excitability by combining brain stimulation with electromyography (EMG). Here, we examined whether global motor inhibition during selective stopping can be measured peripherally and with high temporal resolution using EMG alone. Eighteen participants performed a bimanual anticipatory response inhibition task with their index fingers while maintaining a tonic contraction of the task-irrelevant abductor digiti minimi (ADM) muscles. A time series analysis of the ADM EMG signal revealed transient inhibition during failed stopping compared to go response trials 150 ms to 203 ms following the stop signal. The pattern was observed in both hands during bimanual stop-all trials as well as selective stop-left and stop-right trials of either hand. These results indicate that tonic muscle activity is sensitive to the effects of global motor suppression even when stopping fails. Therefore, EMG can provide a physiological marker of global motor inhibition to probe the time course and extent of stopping processes.Significance Statement The ability to stop ongoing actions is disrupted in a variety of brain disorders, and failing to stop can have dire consequences for personal safety. Successfully stopping an initiated response has a widespread inhibitory effect on motor system excitability. By measuring activity in task-irrelevant muscles during the performance of a stop task we unveiled a novel signature of transient motor system inhibition when stopping fails. The pattern was observed during attempts to selectively and non-selectively stop actions. This temporally precise signature of peripheral inhibition may be leveraged to better examine candidate neural mechanisms, and our non-invasive approach is well-suited for tracking inhibitory control deficits in clinical populations.