Dopamine appetite and cognitive impairment in attention deficit/hyperactivity disorder.
The underlying defects in ADHD (Attention Deficit/Hyperactivity Disorder) are not yet clear. The current paper tests three existing theories: State Regulation, Cognitive Deficit, and Temporal Difference (TD) learning. We present computational simulations of the Matching Familiar Figures Task and compare these with the experimental results reported by Sonuga-Barke (2002). The TD model contains four parameters: the learning rate, discounting for future rewards, brittleness (randomness) of behavior, and action bias. The results show that the basic TD model accounts well for control performance in trials of 5 sec, 10 sec, and 15 sec duration; but not for the deficits in ADHD performance at 5 sec and 15 sec. Extending the TD model to incorporate either a state regulation deficit, or working memory deficit and delay in starting trials, can provide a good account of both control and ADHD results, at all trial-lengths. We discuss the significance of the results for theories of ADHD and make suggestions for future experimentation.
Williams
Jonathan
J
Department of Child and Adolescent Psychiatry, Institute of Psychiatry De Crespigny Park, Denmark Hill, London SE5 8AF, UK. johwilliams@hotmail.com
Taylor
Eric
E
D000465:Algorithms; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology / Q000523:psychology*; D002648:Child; D003072:Cognition Disorders / Q000503:physiopathology / Q000523:psychology*; D004298:Dopamine / Q000502:physiology*; D006801:Humans; D008959:Models, Neurological; D013997:Time Factors
D004298:Dopamine