Nucleus Accumbens Shell Dopamine Preferentially Tracks Information Related to Outcome Value of Reward

Abstract

Effective decision-making requires organisms to predict reward values and bias behavior toward the best available option. The mesolimbic dopamine system, including the nucleus accumbens (NAc) shell and core, is involved in this process. While studies support a role of the shell and core in specific aspects of decision-making (e.g., risk, effort, delay), no studies have directly compared dopamine release dynamics in these subregions to cues exclusively signaling the availability of different reward magnitudes. Here, fast-scan cyclic voltammetry (FSCV) was used to compare rapid dopamine release dynamics in the NAc subregions during a magnitude based decision-making task. Rats learned that distinct cues signaled the availability of either a small or large (one or two sugar pellets) reward, and then were given an opportunity to choose their preferred option. We found that peak dopamine release tracked the more preferred (higher magnitude) option in both core and shell subregions. Critically, however, overall (i.e., global) dopamine release was significantly higher and longer lasting in the shell, and tracked the preferred magnitude during the entire cue period. Further, in the shell (not core) dopamine signaling significantly declined immediately at the lever press for reward, but increased during the period of reward consumption. Collectively, the results indicate that while dopamine release in both the core and shell are activated by cues signaling the opportunity to respond for rewards of different magnitudes, dopamine release in the shell plays a differential and unique role in tracking information related to the outcome value of reward.

Significance Statement The nucleus accumbens (NAc) has been shown to facilitate optimal decision-making, however, the precise role of its primary subregions (shell and core) in outcome-based decision-making is unclear. Here, using voltammetric recording methods in behaving rats, we show preferential real-time dopamine signaling within the NAc shell, compared with the core, during a well-learned magnitude-based decision-making task. Collectively, these findings demonstrate that dopamine in the NAc shell plays a unique role in tracking information related to reward outcome value.