Examining procedural learning and corticostriatal pathways for individual differences in language: testing endophenotypes of DRD2/ANKK1

Abstract

ABSTRACTThe aim was to explore whether genetic variation in the dopaminergic system is associated with procedural learning and the corticostriatal pathways in individuals with developmental language impairment (DLI). We viewed these two systems as endophenotypes and hypothesised that they would be more sensitive indicators of genetic effects than the language phenotype itself. Thus, we genotyped two single nucleotide polymorphisms in DRD2/ANKK1, and tested for their associations to the language phenotype and the endophenotypes. Results showed that individuals with DLI revealed poor procedural learning abilities and abnormal structures of the basal ganglia. Genetic variation in DRD2/ANKK1 was associated with procedural learning and microstructural differences of the caudate nucleus. The association of the language phenotype with DRD2/ANKK1 polymorphisms was non-significant, but the language phenotype was significantly associated with the endophenotypes. We suggest procedural learning and the corticostriatal pathways as effective endophenotypes to aid molecular genetic studies searching for genes predisposing to DLI.