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.
Department of Child and Adolescent Psychiatry, Institute of Psychiatry De Crespigny Park, Denmark Hill, London SE5 8AF, UK. johwilliams@hotmail.com
Jonathan
J
Williams
Eric
E
Taylor
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