Perceptual Surprise Aides Inhibitory Motor Control
Neurophysiological studies of cortico-motor excitability have shown that unexpected sounds are followed by motor inhibition. In a recent study, Leiva, Parmentier, Elchlepp, and Verbruggen (2015) derived a prediction from these findings: unexpected, task-irrelevant sounds should increase the ability to withhold motor responses in a Go/NoGo task. Contrary to that prediction, they found that playing unexpected sounds before NoGo-stimuli decreased the likelihood of successful motor inhibition. However, we here argue that the relative timing of unexpected events relative to NoGo-related motor activity is key. Cortico-motor inhibition can be found only until ∼150 ms after the onset of unexpected sounds. Therefore, since Leiva et al. (2015) placed their sounds 200 ms prior to NoGo-stimuli, the inhibitory influence of unexpected sounds may have fully abated before the critical inhibitory period. Consequently, we here repeated their study, with 1 key change: task-irrelevant sounds were presented 50 ms after NoGo-stimulus onset, which ensures that cortico-motor inhibition takes place when motor inhibition is needed. Across 4 experiments, this changed timing produced the results predicted by the previous cortico-motor suppression findings: More responses were successfully withheld after unexpected sounds. These data provide new evidence for the fact that unexpected events can engage an inhibitory control process and benefit motor inhibition.