Delusions, superstitious conditioning and chaotic dopamine neurodynamics.

Excessive mesolimbic dopaminergic neurotransmission is closely related to the psychotic symptoms of schizophrenia. A mathematical model of dopamine neuron firing rates, developed by King and others, suggests a mechanism by which excessive dopaminergic transmission could produce psychotic symptoms, especially delusions. In this model, firing rates varied chaotically when the efficacy of dopaminergic transmission was enhanced. Such non-contingent changes in firing rates in mesolimbic reward pathways could produce delusions by distorting thinking in the same way that non-contingent reinforcement produces superstitious conditioning. Though difficult to test in humans, the hypothesis is testable as an explanation for a common animal model of psychosis--amphetamine stereotypy in rats. The hypothesis predicts that: (1) amphetamine will cause chaotic firing rates in mesolimbic dopamine neurons; (2) non-contingent brain stimulation reward will produce stereotypy; (3) non-contingent microdialysis of dopamine into reward areas will produce stereotypy; and (4) dopamine antagonists will block all three effects.