Cognition and control in schizophrenia: A computational model of dopamine and prefrontal function

Behavioral deficits suffered by patients with schizophrenia in a wide array of cognitive domains can be conceptualized as failures of cognitive contro l, due to an impaired ability to internally represent, maintain, and update context information. A theory is described that postulates a single neurob iological mechanism for these disturbances, involving dysfunctional interac tions between the dopamine neurotransmitter system and the prefrontal corte x. Specifically, it is hypothesized that in schizophrenia, there is increas ed noise in the activity of the dopamine system, leading to abnormal "gatin g" of information into prefrontal cortex. The theory is implemented as an e xplicit connectionist computational model that incorporates the roles of bo th dopamine and prefrontal cortex in cognitive control. A simulation is pre sented of behavioral performance in a version of the Continuous Performance Test specifically adapted to measure critical aspects of cognitive control function. Schizophrenia patients exhibit clear behavioral deficits on this task that reflect impairments in both the maintenance and updating of cont ext information. The simulation results suggest that the model can successf ully account for these impairments in terms of abnormal dopamine activity. This theory provides a potential point of contact between research on the n eurobiological and psychological aspects of schizophrenia, by illustrating how a particular physiological disturbance might lead to precise and quanti fiable consequences for behavior. Biol Psychiatry 1999;46:312-328 (C) 1999 Society of Biological Psychiatry.