Substance Abuse is Associated with Reduced Devaluation Sensitivity
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Description: Substance abuse has been linked to impairments in reward processing and decision-making, yet research on the relationship between substance abuse and devaluation of reward is limited. Here, we report findings from two studies that tested whether individual differences in substance abuse behavior predicted reward learning strategies and devaluation sensitivity in a non-clinical sample, and evaluated whether striatal dopamine moderates these associations. Participants in Experiment 1 (N = 66) and Experiment 2 (N = 91) completed subscales of the Externalizing Spectrum Inventory and then performed a two-stage reinforcement learning task that included a devaluation procedure. Spontaneous eye blink rate was used to operationalize striatal tonic dopamine levels. In Experiment 1, correlational analysis revealed a negative relationship between substance abuse and devaluation sensitivity. In Experiment 2, regression modeling revealed that while striatal dopamine levels moderated the relationship between substance abuse and reward learning strategies, substance abuse alone was related to devaluation sensitivity. These results suggest that while striatal dopamine alters incentive salience of reward-action associations during learning, once those associations are established, substance abuse is associated with devaluation independently of variation in tonic striatal dopamine. Thus, substance abuse is not only related to increased habit formation but also to difficulty disengaging from learned habits. Implications for the role of the dopaminergic system in habitual responding in individuals with substance abuse problems are discussed.