Nucleus accumbens shell dopamine mediates outcome value, but not predicted value, in a magnitude decision‐making task

Abstract

Effective decision‐making depends on an animal's ability to predict and select the outcome of greatest value, and the nucleus accumbens (NAc) and its dopaminergic input play a key role in this process. We previously reported that rapid dopamine release in the NAc shell preferentially tracks the “preferred” (i.e., large reward) option during cues that predict the ability to respond for rewards of different sizes, as well as during reward delivery itself. The present study assessed whether shell dopamine release at these discrete times selectively mediated choice behavior for rewards of different magnitudes using optogenetics. Here, using Long Evans TH:Cre± rats we employed selective optogenetic stimulation of dopamine terminals in the NAc shell during either reward‐predictive cues (experiment 1) or reward delivery (experiment 2) in a magnitude‐based decision‐making task. We found that in TH:Cre± rats, but not littermate controls, optical stimulation during low‐magnitude reward delivery during forced choice trials was sufficient to bias preference for this option when given a choice. In contrast, optical stimulation of shell dopamine terminals during low‐magnitude reward‐predictive cues in forced choice trials did not shift free choice behavior in TH:Cre± rats or controls. The findings indicate that preferential dopamine signaling in the NAc shell during reward outcome (delivery), but not reward‐predictive cues are sufficient to influence choice behavior in our task supporting a causal role of dopamine in the NAc shell in reward outcome value, but not value‐based predictive strategies.

Disentangling the role of NAc D1 and D2 cells in hedonic eating

“…Indeed, when considering the hedonic shifting task, we found that activating NAc shell D1 cells led to a long-lasting shift in preference (i.e. beyond optogenetic-activation days) while Sackett, Moschak [ 96 ] have shown that if triggering dopamine release in the NAc shell by activating dopamine terminals in this subregion, thus activating D1 cells while inhibiting D2 cells, preference is temporary (i.e. only observed on optogenetic days).…”

“…Previous studies have shown that NAc shell dopamine release during reward delivery, but not during the preceding cue, increases preference for the dopamine-release-associated reward [ 96 ]. This would mean that activating D1 cells and/or inhibiting D2 cells during reward delivery but not during cue delivery would possibly increase preference.…”

Social isolation postweaning alters reward-related dopamine dynamics in a region-specific manner in adolescent male rats

“…Moreover, given that the isolated subjects showed a significant increase in dopamine levels in the shell of the NAc with acute presentation of the novel palatable food, this pathway appears to predominate in processing the rewarding value of stimuli for this group condition. The shell of the NAc has been shown to regulate processing for outcome, but not predictive, value of rewards, in addition to risk-taking behavior ( Freels et al, 2020 ; Sackett et al, 2017 , 2020 ). Interestingly, increased phasic release of dopamine in the NAc shell is associated with a risk-taking phenotype, as opposed to a risk-averse phenotype ( Freels et al, 2020 ).…”

Glucose Sensing in the Hepatic Portal Vein and Its Role in Food Intake and Reward

“…Portal glucose infusions stimulate dopamine release in the nucleus accumbens shell, 55 , 56 which is involved in tracking reinforcer value, representing reward-guided motivation, and associating contextual elements with rewarding stimuli. 57 , 58 , 59 , 60 The fact that glucose detected in the HPV increases dopamine in the nucleus accumbens shell argues that it is reinforcing and may help the animal link the nutrient value of the glucose with sensory stimuli such as taste, flavor, and context. Consistently, glucose (but not mannitol) infusions in the HPV condition a place preference in rats, 55 demonstrating the ability of HPV glucose to support learning about contextual cues, in addition to flavor/taste cues.…”