Parametric study of dopaminergic neuromodulatory effects in a reduced model of the prefrontal cortex

Our on going studies have sought to simulate circuit properties of the mesocortical dopaminergic system. This article describes a reduced model which elucidates the essential nature of dopaminergic modulation in the prefrontal cortex (PFC). Simulating a delayed-response task, we observed that the delay-period activity of the model neurons follows an inverted-U-shaped curve according to the increase in the dopamine level. Subsequent analysis showed that the inverted-U-shaped activation of the model PFC neurons derives from a supercritical pitchfork bifurcation, the formation of which requires synergism between the modulation of the pyramidal-interneuron connection and that of the interneuron's excitability.