Positron emission tomography neuroimaging for a better understanding of the biology of ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a neurobehavioral disorder characterized by inappropriate symptoms of inattention, impulsivity and motor restlessness. Converging data from neuropsychological, genetic, neurochemical and pharmacological studies have implicated fronto-striatal network abnormalities as the likely cause of ADHD. The functional imaging field has evolved rapidly providing unprecedented tools to examine questions regarding the pathophysiology of ADHD and the biological effects of medications used to treat it. Positron emission tomography (PET) provides unique quantitative information on the spatial resolution of radiolabelled molecules in the brain of patients or healthy subjects allowing the longitudinal assessment of physiological parameters such as binding potential over extended periods of time. The main goal of this review is to provide an overview of PET studies performed in ADHD patients, discuss their relative strengths and weaknesses and show how they can complement one another to enable a better understanding of the neurobiology and the neuropharmacology of this disease.