Abstract
Background: Anhedonia leads to reduced pleasure and interest, and may result from altered reward-based decision-making processes. Whereas research with anhedonic individuals typically focuses on tasks to choose between options, daily life involves situations where reward rate varies and decisions evolve over time. In this scenario, foraging models provide a framework in which individuals must consider the rewards they are currently receiving (foreground) and weigh them against potential rewards available elsewhere (background/environment).
Methods: In this study, we aimed to evaluate reward-based decision making of anhedonic (vs. non-anhedonic) individuals using a foraging task in which optimal decisions are described by a normative model, and investigate whether changes in reward environment could impact the decisions as a function of anhedonia, measured by leaving time and reward at the time of leaving.
Results: A total of 94 individuals (mean age = 24yo, SD = 7.85) were allocated to low anhedonic (n = 45; mean MADRS score = 22.1) and high anhedonic (n = 49; mean MADRS score = 36.7) groups. Findings indicate that individuals with higher levels of anhedonia show suboptimal decision-making processes in both leaving time (p = 0.005, η2 = 0.064) and reward rate at leaving time (p = 0.005, η2 = 0.12). However, contrary to initial hypotheses, these individuals did not demonstrate reduced sensitivity to environmental changes but rather displayed a consistent delay in leaving all patch types.
Conclusion: Results suggest that anhedonia is associated with underestimation of the value of the background reward environment, but preserved abilities to utilize reward information for making foraging decisions. This task might be valuable for measuring key constructs within the NIMH Positive Valence Systems domain, including Reward Responsiveness and Reward Valuation.