In young adults, reward sensitivity quadratically relates to genetically predicted striatal dopamine (2014)

Undergraduates: Scott Oppler, Eleanor A. Steel Christopher T. Smith Mary Katherine Kelm Michael H. Parrish

Faculty Advisor: Charlotte Boettiger
Department: Psychology & Neuroscience

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Striatal dopamine (DA) has been extensively implicated in reward related processes. We assessed striatal DA variations and delay discounting (DD) behavior in humans by investigating two functional polymorphisms in genes associated with striatal DA signaling. First, the DA transporter (DAT), which is the primary mediator of DA clearance in the striatum; a variable nucleotide repeat polymorphism in the DAT gene is associated with variation in DAT expression, with the 9 repeat variant yielding greater DAT expression relative to longer repeats. Second, a single nucleotide polymorphism in the DA D2 receptor (DRD2) gene linked to variation in striatal DRD2 availability, with the ¿T¿ variant showing greater DRD2 availability relative to ¿C¿ variants. We assessed intertemporal monetary reward choice behavior using a DD task and investigated whether these genetic variations could account for significant inter-individual variance in DD behavior. Among emerging adults (ages 18-25), we observed a significant DAT¿DRD2 interaction effect on the sensitivity of intertemporal choice to reward magnitude that followed a quadratic function of genetically predicted tonic striatal DA. Those with genetically predicted intermediate DA showed greater reward sensitivity relative to those with predicted high and low DA phenotypes. This relationship was not observed among adults (ages 26-40). These results suggest that striatal DA signaling modulates reward-related decision-making in emerging adults.