INTRODUCTION: Neuropharmacological and human clinical studies have suggested that the dopaminergic system of the brain is substantively involved in normal and pathological phenotypes of attention. Dopamine transporter gene (DAT1) was proposed as a candidate gene for Attention‑Deficit/Hyperactivity Disorder (ADHD). AIM(S): To investigate the effect of the DAT1 gene on performance in the several attentional tasks. METHOD(S): ADHD and healthy children and teenagers aged 9 – 16 were evaluated using tests and procedures involving attentional switching, selective and sustained attention (Test of Everyday Attention, TEA-Ch and Sustained Attention to Response Test, SART), and also three attentional networks – alerting, orienting, and executive attention (Attention Network Test, ANT). DAT1 polymorphism analysis was performed by polymerase chain reaction on saliva samples provided by subjects. ADHD children performed significantly worse in comparison to healthy controls in most of the tasks, demonstrating deficits in various attention processes which were persistent within the examined age range. The results showed an effect of improvement in almost all indices of attentional processes with increasing age in both ADHD and control groups. RESULTS: The results revealed a significant main effect of DAT1 genotype for switching, wherein subjects carrying the 9R allele displayed worse performance in comparison to children with 10R/10R and 10R/11R genotypes. A similar effect of genotype was observed for orienting, which was not disturbed in ADHD subjects. No association between ADHD and the DAT1 polymorphism, and no interaction of DAT1 genotype and ADHD diagnosis were found. CONCLUSIONS: DAT1 is associated with attentional switching and orienting. ADHD is associated with deficits in primary functions that are distinct from those associated with the DAT1 gene polymorphism. FINANCIAL SUPPORT: This research was supported by National Science Centre Poland Grants 2011/01/D/ NZ4/04958 and 2015/17/N/HS6/03020.
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