Dopamine, norepinephrine, and the management of sensorimotor bindings: individual differences in updating of stimulus–response episodes are predicted by DAT1, but not DBH5′-ins/del

Evidence suggests that the flexibility of managing (creating and updating) stimulus–response bindings is driven by the dopaminergic system. Given that striatal dopamine (DA) plays a crucial role in the updating of working memory, the present study tested whether individual differences in the efficiency of updating stimulus–response episodes (event files) are predicted by differences in genetic predisposition related to the efficiency of the striatal dopaminergic pathway. In view of contrasting claims that stimulus–response binding is related to norepinephrine, we also considered genetic predispositions regarding noradrenergic pathways. In a sample of 100 healthy adults, we studied whether the degree to which stimulus–response bindings affect ongoing performance is predicted by polymorphisms of the dopamine transporter gene (DAT1, associated with striatal DA levels) and DBH5′-ins/del (strongly correlated with dopamine beta-hydroxylase, the enzyme catalyzing the dopamine-norepinephrine conversion). The performance of 9-repeat carriers of the DAT1 gene was more affected by stimulus–response bindings than the performance of 10/10 homozygotes was, while DBH5′-ins/del polymorphism was not related to performance. This outcome pattern suggests a crucial role of the nigrostriatal dopaminergic pathway in the flexible management of stimulus–response episodes, whereas norepinephrine does not seem to play a role.