Impact of effort and expectancy on reward-related event-related potentials: Evidence from a novel effort and expectancy paradigm (EEP).

Abstract

Effort justification theories posit that reward is more salient after exerting effort, while effort discounting theories suggest that effort is costly and makes outcomes less salient. Reward expectation can also impact salience and influence effort and reward dynamics. To investigate the influence of both effort and expectancy of reward timing on reward-locked neural indices (i.e., RewP and P300), we created a novel monetary reward task (i.e., Effort & Expectancy Paradigm [EEP]) that modulates high and low amounts of physical effort (or passive waiting) and reward expectancy (i.e., countdown compared with no countdown trials). Eighty-two undergraduate students (61.7% female) completed surveys and the EEP during a continuous EEG recording. Principal component analysis (PCA) was used to better understand the temporal and spatial subcomponents of reward-related ERPs, resulting in RewP and P300 factors. High effort trials resulted in larger RewP and P300 compared with waiting, and both the RewP and P300 were larger when reward was less expected (i.e., no countdown) compared with when reward was more expected (i.e., countdown). P300 main effects were further qualified by unique interactions between effort (press or wait), amount of effort (high or low), and expectancy (countdown or no countdown). Finally, only RewP emerged as a neural correlate of self-reported hedonic capacity. Present results suggest that salient stimuli (e.g., effortful and unexpected reward timing) enhance neural measures of reward consumption and increase allocation of cognitive resources. Reduced RewP elicited from this novel task might reflect disrupted reward processing in individuals experiencing elevated anhedonia.