Neuroimaging of attention-deficit hyperactivity disorder

Neuroimaging in attention-deficit hyperactivity disorder (ADHD) has advanced to the degree that it can now be characterized as scientific enquiry, as it is now possible to formulate explicit falsifiable hypotheses about individual brain regions and circuits. Although methodologic problems remain, there is increasing agreement on the role of the prefrontal-striatal-thalamo-cortical circuit in ADHD, with a preponderance of the evidence suggesting that the right-sided circuit is primary, at least at the level of the basal ganglia. This convergence is all the more remarkable given the many obstacles that have needed to be overcome, chief among them the pleiotropic nature of the disorder. An emphasis on subtyping patient populations by comorbidity, age, and sex, and eventually by meaningful biologic variables such as relevant genotypes, will be crucial in sorting out which other regions are intrinsically related to ADHD, and which are associated with comorbid conditions.