Research review: dopamine transfer deficit: a neurobiological theory of altered reinforcement mechanisms in ADHD.

This review considers the hypothesis that changes in dopamine signalling might account for altered sensitivity to positive reinforcement in children with ADHD. The existing evidence regarding dopamine cell activity in relation to positive reinforcement is reviewed. We focus on the anticipatory firing of dopamine cells brought about by a transfer of dopamine cell responses to cues that precede reinforcers. It is proposed that in children with ADHD there is diminished anticipatory dopamine cell firing, which we call the dopamine transfer deficit (DTD). The DTD theory leads to specific and testable predictions for human and animal research. The extent to which DTD explains symptoms of ADHD and effects of pharmacological interventions is discussed. We conclude by considering the neural changes underlying the etiology of DTD.