Distinct roles of anterior cingulate and subcortical regions supporting effort evaluation versus preparation

Cognitive effort encompasses the mental exertion invested to achieve a goal as well as the experienced cost associated with that exertion. The dopaminergic midbrain regions (i.e., ventral tegmental area/substantia nigra), ventral striatum, and the anterior cingulate cortex have all been broadly implicated in effort regulation. However, less is known about the role of these regions in dissociable subprocesses such as effort evaluation versus effort preparation. In this preregistered functional MRI study with concurrent pupil-tracking, we disentangled the evaluation and preparation phase of reward- and effort-based motivation. In the evaluation phase, the typical valuation regions encoded high reward and low effort demand as a motivational factor. In the preparation phase, the anterior cingulate cortex displayed increased activity for demanding high reward trials, while the ventromedial prefrontal cortex responded to demanding trials in general. The dopaminergic midbrain exhibited a positive reward effect only during task execution. The results suggest that when separating evaluation from preparation, regions traditionally thought of as primarily reward-attuned can assign a motivating signal to effort, while the anterior cingulate cortex integrates effort and reward prospect to subserve preparatory control processes.