Injection of a dopamine type 2 receptor antagonist into the dorsal striatum disrupts choices driven by previous outcomes, but not perceptual inference

Decisions are based on a combination of immediate perception and previous experience. If the mapping between actions and outcomes in a context is unpredictable over time, decisions must be made on the basis of immediately available information. Alternatively, if action-outcome mappings can be learned by reinforcement, then this information can be combined with immediately available information. Previous neurophysiological results suggest that frontal-striatal circuits may be involved in the interaction between these processes. The role of dopamine, however, has not been examined directly. We injected locally dopamine type 1 (D1A; SCH23390) or type 2 (D2A; Eticlopride) antagonists or saline into the dorsal striatum while macaques performed an oculomotor sequential decision making task. Choices in the task were driven by perceptual inference and/or reinforcement of past choices. We found that the D2A affected decisions based on previous outcomes. When we fit Rescorla-Wagner models, the inverse temperature decreased after D2A injections into the dorsal striatum compared with a pre-injection period. We found that neither the D1A nor saline injections affected behavior. Overall, our results suggest D2Rs in the striatum control the inverse temperature in reinforcement learning.