Association between dopamine D4 receptor (DRD4) gene polymorphisms and novelty-elicited auditory event-related potentials in preschool children.

We investigated associations of the exon III repeat and the -521 C/T polymorphisms of the DRD4 gene with novelty-elicited auditory ERP components and behavioral resistance to distraction in 57 healthy, typically developing 6-year-old children. Dopamine-related gene polymorphisms have previously been linked to processes directing focused attention. We did not find associations between the 7-repeat allele or the T.7 haplotype and the early ERP responses suggesting that DRD4 polymorphisms did not affect the detection of novelty. However, the same polymorphisms affected the late negative components (LN1 and LN2). Late negativities elicited by deviant and novel sounds have been regarded as reflecting reorientation after distraction or additional processing of new information. Children carrying the T.7 haplotype had significantly smaller LN1 and LN2 amplitudes. The presence of the T.7 haplotype also significantly enhanced behavioral resistance to distraction. We suggest that less distraction in T.7 carriers led to less reorienting activity (reflected by the LN components). We also speculate that activation of less sensitive and fewer D4 receptors (as with the T.7 haplotype) is less effective in modulating GABAergic inhibitory signaling, which in turn is reflected in smaller LN amplitudes.