Cortical contributions to attentional orienting and response cancellation in action stopping
Action cancellation involves the termination of planned or initiated movement. Contemporary models of action cancellation, such as the Pause-then-Cancel model, propose that this occurs via a two-stage process, initiated in the cortex by the pre-supplementary motor area (preSMA) and inferior frontal gyrus (IFG). Previous experimental work using electromyography (EMG) has identified that the cancellation of actions can involve the partial activation of the responding muscles, which does not result in an overt behavioural response. In this study, we used functional near-infrared spectroscropy (fNIRS) to investigate the neural correlates of these partial responses in a modified stopping task (a response- and stimulus-selective stop-signal task), controlling for the attentional effects that have long confounded action cancellation research by comparing responses to stop stimuli with those to ignore stimuli. We identified stopping-related activity in the preSMA but not the IFG, consistent with predictions of the Pause-then-Cancel model. Additionally, we observed increased preSMA activity in trials where no partial responses occurred, potentially due to the cumulative effect of different inhibitory processes in those trials. This study also highlights the utility of combining fNIRS and EMG in examining the cortical correlates and dynamic processes involved in action cancellation.