Dopaminergic polymorphisms C957T and ANKK1 contribute to distinct aspects of delay discounting
Amy T Nusbaum1, John M Hinson1, Paul Whitney1; 1Washington State University
Impulsivity is characterized in part by the tendency to make decisions that lead to immediate reward without consideration of potential future consequences. Excessive impulsivity has been conceptualized as an imbalance between top-down processes, driven by the prefrontal cortex, and bottom-up processes, driven by regions including the striatum. Thus, neurochemical modulation of impulsivity may rely on those two regions. Further, impulsivity as measured by delay discounting tasks can be altered using constraints such as working memory loads, but the biological factors that confer resiliency or vulnerability to such constraints have not been identified. We examined the role of dopamine-related genetic polymorphisms in impulsivity under baseline conditions and while engaged in a working memory task. Participants (n=121) were genotyped for COMT (rs4680), a polymorphism that affects dopamine in the prefrontal cortex, C957T (rs6277), and ANKK1 (rs1800497), polymorphisms that affect dopamine in the striatum. Participants two conditions of a delay discounting task involving choices of hypothetical amounts of money while maintaining either a relatively small or relatively large working memory load of randomly selected digits. Using a repeated measures ANOVA, we found that the C957T C allele increased discounting of delayed amounts of money, consistent with more impulsive decision making, while the ANKK1 A1 allele increased discounting rates only when individuals were undergoing a working memory load. These results provide further support for the role of genetics in impulsivity, while also suggesting a potential biomarker that may confer vulnerability to factors that alter impulsivity, such as working memory loads and stress.
Topic Area: EXECUTIVE PROCESSES: Monitoring & inhibitory control