title: Origins of altered reinforcement effects in ADHD.
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.
authors.affiliation: Centre for Advanced Study (CAS) at the Norwegian Academy for Science and Letters, Oslo, Norway. e.b.johansen@medisin.uio.no.
authors.forename: Espen Borgå
authors.initials: EB
authors.lastname: Johansen
authors.forename: Peter R
authors.initials: PR
authors.lastname: Killeen
authors.forename: Vivienne A
authors.initials: VA
authors.lastname: Russell
authors.forename: Gail
authors.initials: G
authors.lastname: Tripp
authors.forename: Jeff R
authors.initials: JR
authors.lastname: Wickens
authors.forename: Rosemary
authors.initials: R
authors.lastname: Tannock
authors.forename: Jonathan
authors.initials: J
authors.lastname: Williams
authors.forename: Terje
authors.initials: T
authors.lastname: Sagvolden