Mechanisms of Proactive Adaptation in a Rewarded Response Inhibition Task: Executive, Motor, or Attentional Effects?

A growing number of studies have demonstrated the effects of reward motivation on inhibitory control performance. However, the exact neurocognitive mechanisms supporting these effects are not fully elucidated. In this preregistered study, we test the hypothesis that changes in speed-accuracy trade-off across contexts that alternatively incentivize fast responses versus accurate inhibition rely on a modulation of proactive inhibitory control, a mechanism intended to lock movement initiation in anticipation of stimulus presentation. Thirty healthy participants performed a modified Go/NoGo task in which the motivation to prioritize Go vs. NoGo successes was manipulated using monetary rewards of different magnitudes. High-density EEG was recorded throughout the task. Source-space analyses were performed to track brain oscillatory activities consistent with proactive inhibitory control. We observed that participants adapted their behavior to the motivational context but found no evidence that this adaptation relied on a modulation of proactive inhibitory control, hence failing to provide support for our pre-registered hypothesis. Unplanned analyses of brain-behavior relationships suggested an association between faster reaction times and enhanced top-down attention to the stimuli associated with larger rewards, as well as between increased commission error rates and stronger motor activations when Go stimuli were associated with larger rewards. The latter was related to inter-individual differences in trait reward responsiveness. These results highlight the need to carefully parse the different contributing mechanisms when studying the influence of reward motivation on inhibitory performance in impulsivity disorders. Exploratory results suggest alternative mechanisms that may be directly tested in further studies.