Brain dopamine and individual differences in a behavioural measure of reward responsiveness: A pharmacogenetic study

Abstract

Trait reward responsiveness has been theoretically linked to individual differences in the brain’s dopaminergic reward circuitry. Here, we investigated the effect of dopaminergic genes and a pharmacological modulation of dopamine activity on a laboratory-based measure of reward responsiveness. After receiving either placebo or the selective dopamine D2 receptor blocker sulpiride (200 mg, double-blind administration) 201 male students completed a probabilistic reward task in which two correct responses were differentially reinforced. As expected, the bias for the more frequently reinforced response increased across the three task blocks. In addition, the magnitude of this increase depended on participants’ catechol- O -methyltransferase (COMT) Val158Met genotype: Homozygous individuals (Val/Val and Met/Met carriers) showed stronger increases in response bias than heterozygous individuals (Val/Met carriers) and were, thus, more responsive to the reward contingencies. However, no significant effects of sulpiride on reward bias were observed. The results provide mixed support for dopamine theories of trait reward responsiveness.