Performance in the Wisconsin card sorting test and the C957T polymorphism of the DRD2 gene in healthy volunteers

Introduction: Previous studies have associated a decreased striatal D2 dopamine receptor (DRD2) binding with impaired performance in cognitive tasks. In vivo studies have found a lower DRD2 binding associated with the CC genotype of the C957T single nucleotide polymorphism ( SNP) of the DRD2 gene. Objective: The aim of this study was to investigate the relationship between executive functions and the C957T DRD2 SNP. We hypothesized that the CC genotype would be associated with a poorer executive functioning. Methods: Our sample consisted of 83 healthy volunteers ( 28 males and 55 females; mean age 25.2, SD 1.7 years). To assess executive functions, the Wisconsin Card Sorting Test was used, considering the variables perseverative errors, perseverative responses, and number of categories achieved. The genotype distribution was 13 CC, 41 CT, and 29 TT, satisfying Hardy-Weinberg equilibrium. Results: Carriers of the CC genotype, compared with carriers of the CT/TT genotypes, achieved significantly fewer categories (5.00 vs. 5.81; p = 0.004), made a greater number of perseverative errors (13.46 vs. 8.39; p = 0.018), and had a greater number of perseverative responses (14.92 vs. 8.94; p = 0.014). Conclusions: Our results support the hypothesis that the C957T DRD2 SNP may influence cognitive performance through its repercussions on central dopaminergic function. Copyright (c) 2006 S. Karger AG, Basel.