ADHD heterogeneity is one of the major issues to be found in a study evaluating the neurobiological pinning of a new ADHD phenotype known as ADHD restrictive inattentive (ADHD-RI) and comparing ADHD-RI, ADHD inattentive, combined ADHD and TD individuals using genetic data involving dopamine transporters and receptor gene polymorphisms (SLC6A3 and DRD4) and by performing fMRI (go/no task). The gene discussed is SLC6A3; the disease is attention deficit-hyperactivity disorder.