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. Key Points Successfully stopping an initiated response globally suppresses the motor system. Using electromyography of tonic muscle activity, we show inhibition spills over to task-irrelevant muscles during failed stopping. The electromyographic pattern of inhibition is transient, lasting from approximately 150 to 203 ms following a stop signal when stopping fails. The time course of the peripheral suppression of muscle activity may be leveraged to more precisely examine candidate neural mechanisms. This non-invasive measure of motor system inhibition may be useful for tracking inhibitory control deficits in clinical populations.