Conditional Routing of Information to the Neocortex: A Network Model of Basal Ganglia Function

The basal ganglia are widely regarded as playing a central role in cognition, being involved is such general functions as action selection and reinforcement learning. Here, we present a model exploring the hypothesis that the basal ganglia implement a conditional information routing circuit, where cortical signals are gated and subsequently relayed onto different pathways projecting to the prefrontal cortex. It also accounts for the existence of two distinct branches (pallidal and nigral) of the direct pathway, by assuming that they are used to carry separately content and routing information. A possible mechanism is described by which the indirect pathway can control the release of dopamine along the nigrostriatal pathway, generating a signal that the striatum can use to produce novel stimulus-response associations by internalizing cortical representations. In a series of simulations, it is shown how the model can perform simple stimulus-response tasks, develop automatic behaviors, and provide an account of impairments in Parkinon's and Huntington's disease. Finally, it is also discussed how the proposed model’s mechanisms relates to production systems, a widely adopted formalism for human cognition, and how the reward signals carried by the mesolimbic pathway can be integrated to exert fine control over action selection.