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We focused on how the rat uses olfactory cues in a single‐pellet reaching task, which is composed of three successive learned responses, Orient, Transport, and Withdrawal. Orient comprised: front wall detection, slot localisation, and nose poke until reach start. High‐speed video‐recording enabled us to describe the temporal features of this sequence in controls vs. 3–5 and 12–14 days after bilateral bulbectomy in trials with (P trial) vs. without (no‐P trial) pellet. In controls, the full sequence was complete in P trials, while it was interrupted after Orient in no P‐trials. After bulbectomy, the full sequence was seen in both P and no‐P trials at days 3–5 and 12–14 and there was an increase in Orient duration due to the increased time in slot/shelf localisation. Unlike in controls, in anosmic rats, the first nose contact with the front wall took place below the slot/shelf level, and the number of nose touches together with the number of whisker cycles was significantly higher at 3–5 but not at 12–14 days. The relationship between nose touches and whisker cycles was linear in all experimental conditions. Bulbectomy resulted in no changes in the Transport duration or the time the paw spent out of the slot. These findings suggest that olfaction allows the animal to orient itself in pellet localisation, and offers insight into the contribution of olfaction during different stages of natural behaviour in skilled reaching task. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]