The influence of effort expenditure on the neurophysiological substrates of reward processing in early adolescence.

Reward and motivation are two processes that drive goal-directed behaviors and are closely linked to the development of psychopathology. One behavioral measure of motivation is effort expenditure-the amount of effort exerted to attain a desirable outcome. In adults, higher effort expenditure has been associated with heightened neural responses to reward cues but diminished responses to reward anticipation and feedback. However, it is unclear whether similar patterns exist in early adolescence, a critical period for the development of reward- and motivation-related processes. Applying event-related potentials to a novel Effort-Doors task, we explored the effort-reward relationship in a community sample of 92 10-to-13-year-olds (53 females, mean/SD of age = 12.06/1.2 years). Behaviorally, youths were slower to respond in high-effort trials; they were also more likely to switch their choices following higher effort and reward losses in previous trials. At the neural level, greater effort expenditure increased youths' attention to reward cues (indexed by a larger cue-P3) and decreased the overall value associated with the reward trial (indexed by a smaller RewP). Effort did not influence feedback-elicited P3 or the late positive potential (LPP). Our work provided important preliminary evidence on the distinct effects of effort on different stages of reward processing in early adolescents. Future work is needed to better understand the underlying mechanisms of effort-based reward processes, their development across adolescence, and how they relate to behavior.