COMT Val158Met genotype and the common basis of error and conflict monitoring.

The present study investigated the possibility that different aspects of performance monitoring share a common dopaminergic foundation. For this purpose we analyzed the influence of the COMT Val(158)Met polymorphism on electrophysiological markers of conflict and error monitoring, respectively. An EEG was recorded while 65 healthy subjects completed a response-conflict evoking task. In the event-related potential (ERP), both the conflict-N400 as well as the error-related negativity (ERN) were diminished in homozygous carriers of the Met allele. Moreover, the shared variance of both deflections was substantially explained by the COMT Val(158)Met genotype. These findings suggest that the relation between error- and conflict-related processes in the medial frontal cortex is mediated by a common molecular mechanism, namely the individual magnitude of phasic dopaminergic transmission.