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Open Access Highly Accessed Review

Origins of altered reinforcement effects in ADHD

Espen BorgÄ Johansen12*, Peter R Killeen13, Vivienne A Russell14, Gail Tripp15, Jeff R Wickens16, Rosemary Tannock17, Jonathan Williams1 and Terje Sagvolden12

Author Affiliations

1 Centre for Advanced Study (CAS) at the Norwegian Academy for Science and Letters, Oslo, Norway

2 Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway

3 Department of Psychology, Arizona State University, Tempe, AZ 85287-1104, USA

4 Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory 7925, South Africa

5 Human Developmental Neurobiology Unit, Okinawa Institute of Science and Technology, Okinawa, Japan

6 Neurobiology Research Unit, Okinawa Institute of Science and Technology, Okinawa, Japan

7 Research Institute of The Hospital for Sick Children, University of Toronto, Canada

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Behavioral and Brain Functions 2009, 5:7  doi:10.1186/1744-9081-5-7

Published: 18 February 2009

Abstract

Attention-deficit/hyperactivity disorder (ADHD), characterized by hyperactivity, impulsiveness and deficient sustained attention, is one of the most common and persistent behavioral disorders of childhood. ADHD is associated with catecholamine dysfunction. The catecholamines are important for response selection and memory formation, and dopamine in particular is important for reinforcement of successful behavior. The convergence of dopaminergic mesolimbic and glutamatergic corticostriatal synapses upon individual neostriatal neurons provides a favorable substrate for a three-factor synaptic modification rule underlying acquisition of associations between stimuli in a particular context, responses, and reinforcers. The change in associative strength as a function of delay between key stimuli or responses, and reinforcement, is known as the delay of reinforcement gradient. The gradient is altered by vicissitudes of attention, intrusions of irrelevant events, lapses of memory, and fluctuations in dopamine function. Theoretical and experimental analyses of these moderating factors will help to determine just how reinforcement processes are altered in ADHD. Such analyses can only help to improve treatment strategies for ADHD.