DOPAMINE AND THE MECHANISMS OF COGNITION - PART-I - A NEURAL-NETWORK MODEL PREDICTING DOPAMINE EFFECTS ON SELECTIVE ATTENTION

Background: Dopamine affects neural information processing, cognition, and behavior; however, the mechanisms through which these three level s of function are affected have remained unspecified We present a para llel-distributed processing model of dopamine effects on neural ensemb les that accounts for effects on human performance in a selective atte ntion task, Methods: Task performance is stimulated using principles a nd mechanisms that capture salient aspects of information processing i n neural ensembles. Dopamine effects are simulated as a change in gain of neural assemblies in the area of release. Results: The model leads to different predictions as a function of the hypothesized location o f dopamine effects. Motor system effects are simulated as a change in gain over the response layer of the model. This induces speeding of re action times but an impairment of accuracy, Cognitive attentional effe cts are simulated as a change in gain over the attention layer. This i nduces a speeding of reaction times and an improvement of accuracy, es pecially, at very fast reaction times and when processing of the stimu lus requires selective attention. Conclusions: A computer simulation u sing widely accepted principles of processing in neural ensembles can accountfor reaction time distributions and time-accuracy curves in a s elective attention task. The simulation can be used to generate predic tions about the effects of dopamine agonists on performance. An empiri cal study evaluating these predictions is described in a companion pap er. (C) 1998 Society of Biological Psychiatry.