Accumbal cholinergic interneurons regulate decision making or motor impulsivity depending on latent task state

Abstract

Dopaminergic transmission within the nucleus accumbens is broadly implicated in risk/reward decision making and impulse control, and the rat gambling task (rGT) measures both behaviours concurrently. While the resulting indices of risky choice and impulsivity correlate at the population level, dopaminergic manipulations rarely impact both behaviours uniformly, with changes in choice more likely when dopaminergic transmission is altered during task acquisition. Although the task structure of the rGT remains constant, the importance of accumbal dopamine signals relevant for reward prediction versus impulse control may vary over time; the former should dominate while learning which option maximises sugar pellet profits, while the suppression of premature responses becomes more valuable once a decision-making strategy is set and can be exploited. Cholinergic interneurons (CINs) critically control dopamine release within the striatum, and can also encode latent task states deciphered by the frontal cortex. We theorised that aCINs may set the dopaminergic tone of the accumbens to maximise reward learning or impulse control during task acquisition or performance, respectively. Using chemogenetics, we found some support for this hypothesis: activation and inhibition of aCINs once behaviour was stable increased and decreased motor impulsivity in both sexes but had no effect on choice patterns. In contrast, activating and inhibiting aCINs throughout task acquisition did not alter motor impulsivity, but decreased and increased risky choice respectively. However, the former effect was only seen in males and the latter in females. We conclude by proposing a set of testable predictions regarding interactions between acetylcholine and dopamine that could explain these sex differences.