The mediating effect of prefrontal asymmetry on the relationship between the COMT Val(158)Met SNP and trait consummatory positive affect.

The Val(158)Met rs4680 polymorphism in the COMT gene regulates dopamine catabolism in the prefrontal cortex (PFC). Dopamine's involvement in reward experience suggests those with the methionine (Met) variant may exhibit trait-level sensitivity to reward due to more post-synaptic dopamine in the PFC. A physiological mediator of this association may be greater relative left asymmetry in the PFC, a putative biomarker for trait positive emotionality. Electroencephalograms of 120 participants were measured during a task that assesses two aspects of reward processing: pre-reward anticipation and post-reward consummatory affect. Participants provided genetics samples and completed the Temporal Experience of Pleasure Scale (TEPS), which assesses trait-level anticipatory and consummatory positive affect. Met carriers had higher TEPS-Consummatory scores. This effect was mediated by greater relative left activation in the post-reward phase of the task. No effects were observed for the pre-reward phase. Results suggest that frontal asymmetry is an endophenotype between COMT genotype and trait reward responsivity.