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Several studies link the D2 dopamine receptor (DRD2) with executive control and the ability to adapt behavior to changing contextual contingencies in human adults (Roesch-Ely 2005; Rodriguez-Jimenez 2006) and in animal models (Kruzich 2004). The present study examined relations between DRD2 and executive control in human development. Recently, a version of the Trail-Making Task suitable for preschool children was developed, which does not require knowledge of letters or numbers (TRAILS-P; Espy 2004). The Trail-Making Test is a neuropsychological test sensitive to frontal or executive dysfunction (Reitan 1955) where subjects must connect stimuli on a page in sequence, connecting letters only in the non-executive condition, and alternating between numbers and letters in the condition with executive demands. In TRAILS-P Control condition, children stamp a family of 5 dogs in order from smallest to biggest. The Switch condition adds executive demands by requiring children to switch response set by alternating stamping dogs and bones ordered by size. In the Inhibit condition, dogs and bones are present on the page but children must only stamp dog stimuli, requiring suppression of the response set acquired in the Switch condition. For each condition, the number of errors and completion latency are scored. A sample of 98 typically developing preschool children (mean age 4.3 years, range 2.5 to 6 years) completed the TRAILS-P task, and were genotyped on the Taq1A polymorphism linked to the DRD2 gene. The sample included 43 carriers of the higher-risk A1 allele (A1A1: n = 41; A1A2: n = 2) and 55 non-carriers (A2A2). For DRD2, presence of the A1 allele was associated with poorer performance on the switch condition (p < .01 for time, p .17), statistically controlling for age. A1 carriers also made more errors on the Inhibit condition (p < .005). The finding that DRD2 contributes to variation in executive control in young children provides a developmental continuity in this brain-behavior relationship between dopamine genotype and behavioral phenotype, and may be attributable to the lower availability of dopamine receptors associated with the DRD2 A1 genotype.