Conflict resolution and response inhibition: A simultaneous EEG-EMG-pupillometry study

Inhibition in cognitive control has many implications. Behaviorally, the stop signal task is supposedly capturing inhibition of already initiated responses (response inhibition). In contrast, the flanker paradigm supposedly captures the inhibition of several competing responses (competitive inhibition). As the neural mechanisms for these behavioral phenomena are not clear, it begs the question of whether both response inhibition and competitive inhibition draw from a similar inhibitory resource pool and to what extent they might interact. In the current study, the potential interplay between inhibitory mechanisms was investigated in a combined stop-signal flanker task where (in-)congruent flankers were occasionally followed by stop signals. A multimodal task-setup was implemented allowing for examination of behavior, electromyography (EMG), electroencephalography (EEG), and pupillometry to assess different inhibition-related outcome measures. Estimates of response inhibition speed (stop-signal reaction times; SSRTs) indicated an interaction with competitive inhibition, where stopping was faster in incongruent compared to congruent stop conditions. However, this was likely driven by differences at the short stop signal delays, which are susceptible to horse race model violations. Moreover, this interaction was not evident in physiological measures: neither stop-related EMG, EEG nor pupillometry measures showed such congruency modulations. Exploratory analyses showed that a larger pupillometry congruency effect was negatively associated with the congruency effect in SSRTs, suggesting that pupil dilation as a proxy for NE-LC activity might be linked to increased allocation of cognitive control. Taken together, our results do not provide clear evidence for an interaction between response inhibition and competitive inhibition.