Dopamine D2 receptor C957T polymorphism and its phenotypic consequences on executive functions in 8 years old children
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Executive functions (EFs) are a set of cognitive skills that allows goal oriented behaviour. Three principal skills - inhibition, working memory and set-shifting - are thought to modulate higher level functions, such as reasoning. There is evidence for both environmental and genetic factors to set individual level of EFs. Genetic influences are explored especially through analysis of Single Nucleotide Polymorphisms (SNPs). The dopaminergic system has been widely investigated in this sense and in particular, the C957T polymorphism of the Dopamine D2 receptor. We conducted an association study using genetic and neuropsychological data of 8 years old children collected for Trondheim Early Secure Study at Department of Psychology, NTNU. A neuropsychological test for each of the three core EFs was chosen: NEPSY Statue task for inhibition, WISC count backward task for Working Memory and CANTAB Intra/Extra Dimensional task for set-shifting. Genotyping data for a SNP (rs1554929) in complete Linkage Disequilibrium (D=1) with C957T were used. Results suggested that carriers of the T allele were more prone to impulsivity according to the NEPSY Statue test outcomes. The C957T polymorphism did not show an effect on modulation of other neuropsychological tests results. The influence of covariates was tested for the NEPSY Statue test and showed no statistically significant effect. Only sex influenced the NEPSY Statue results independently of the genotype, with males showing lower inhibitory control.