Role of the primate ventral striatum as a neural hub bridging option valuation and action selection

Making appropriate decisions relies on the brain’s capacity to evaluate the expected outcomes of available options and select the most rewarding one. Reinforcement learning theory offers a computational framework for this process, wherein value function represents the value of expected outcomes and is updated by reward prediction errors. The ventral striatum and midbrain dopamine neurons have been regarded as neural substrates for encoding and updating the value function. Extending beyond this framework, we found that the dopamine–ventral striatum system plays a more proactive role in deciding which option to choose. We recorded single-unit activity in macaque monkeys as they sequentially evaluated an option, decided whether to choose it, and expressed that choice through a motor response. Ventral striatum neurons initially encoded option value but gradually shifted their activity to reflect monkey’s choice, as if the ventral striatum itself derives the choice from value information. Moreover, optogenetic facilitation of dopamine input to the ventral striatum as well as electrical stimulation of this region altered monkey’s choice. Our findings reveal a novel function of the ventral striatum as a neural hub that bridges option valuation and action selection, and demonstrate the contribution of dopamine in modulating decision computations within this region.