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

TL;DR

This study shows how the brain's ventral striatum helps turn value assessments into actual decisions, with dopamine playing a key role in this process.

Contribution

The study reveals a new role of the ventral striatum as a neural hub linking value evaluation to action selection.

Findings

Ventral striatum neurons initially reflect option value but later encode action selection.

Dopamine input and electrical stimulation of the ventral striatum influence action selection.

The ventral striatum acts as a bridge between valuation and decision-making processes.

Abstract

Making appropriate decisions relies on the brain’s capacity to evaluate the expected outcomes of available options and select the most rewarding action. The ventral striatum and midbrain dopamine neurons have been implicated in the option valuation process, consistent with the brain’s reinforcement learning theory in which these brain structures encode and update value representations of expected outcomes. Extending beyond this framework, we found that the dopamine–ventral striatum system plays a more proactive role in action selection. We recorded single-unit activity from ventral striatum neurons in macaque monkeys as they sequentially evaluated an option, decided whether to perform an action to choose it, and expressed that motor action. The activity of these neurons initially reflected the value of the option but gradually shifted to reflect monkey’s action selection, as if the ventral striatum translates the value information into the action. Moreover, optogenetic facilitation of dopamine input to the ventral striatum as well as electrical stimulation of this region altered monkey’s action selection. Our findings reveal a previously unappreciated function of the ventral striatum as a neural hub that bridges option valuation and action selection, and demonstrate the contribution of dopamine in the process leading to action selection within this region.

The neural mechanism by which internal value representations guide action selection remains poorly understood. This study shows that the ventral striatum transforms value signals into selection signals, and that dopamine input modulates this process.

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