Neural correlates of reward-directed action and inhibition of action.

Human and non-human primate studies have examined neural responses to action and inhibition of action. However, it remains unclear whether the cerebral processes supporting these two distinct responses are differentially modulated by reward. In a sample of 35 healthy human adults, we examined brain activations to action and inhibition of action in a reward go/no-go task, with approximately ⅔ go and ⅓ no-go trials. Correct go and no-go trials were rewarded with $1 or ¢5 in reward sessions. Behaviorally, reward facilitated go and impeded no-go. A conjunction analysis showed shared activation to rewarded go and no-go responses in the rostral anterior cingulate cortex (rACC) and inferior parietal cortex. A whole-brain two-way ANOVA of response (go vs no-go) and reward (dollar vs nickel) revealed a significant main effect of response, with greater activity for no-go vs go success in the middle frontal cortex and the reversed pattern in the dorsal ACC, insula, thalamus, and caudate. The thalamus and caudate also responded preferentially to dollar relative to nickel reward during go trials. The main effect of reward (dollar > nickel) involved not only regions associated with reward valuation (e.g., medial orbitofrontal cortex - mOFC) but also those implicated in motor control, saliency, and visual attention including the rACC, ventral striatum, insula, and occipital cortex. Finally, the mOFC distinguished go and no-go responses in the dollar but not nickel trials, suggesting a functional bias toward response execution that leads to larger rewards. Together, these findings identified both shared and non-overlapping neural processes underlying goal-directed action and inhibition of action as well as delineated the effects of reward magnitude on such processes.