Figure 1.

(a) Anatomy of corticostriatal circuitry simulated in computational models and used as a framework for studying the roles of these systems in reinforcement learning and decision making. Potential actions in cortex are communicated to the striatum (caudate and putamen). The probabilities of yielding positive vs negative outcomes for these actions are learned as a function of dopaminergic reinforcement signals conveyed to striatonigral (‘Go') and striatopallidal (‘NoGo') neural populations expressing D1 and D2 receptors, respectively. The likelihood of selecting a given action is a function of the relative difference in these populations. In parallel, the hyperdirect pathway from frontal cortex to the STN implements cognitive control by modulating the overall threshold for executing an action as a function of decision conflict. (b) Candidate genetic factors specific to striatonigral and striatopallidal function, posited to alter learning and decision-making function.