What's the occasion? Phasic dopamine signaling and interoception

Phasic dopamine is critically important in reward-related learning and assigns value to actions triggered by cues. Outcomes of actions in turn adjust the probability that a behavior will be repeated. That is, outcomes reinforce behavior-a process that also involves phasic dopamine. The value of actions and their outcomes, though, is ever fluctuating. Internal state-from physiological need through satiation-gates or applies gain to cue-evoked actions and the evaluation of their outcomes. We focus on how interoceptive signals may influence dopamine neurons to modify the phasic signaling underlying cue and reward-directed behaviors. We focus on interoceptive signals that arise from food or fluid deficit since the peripheral hormonal responses to such needs are relatively well established. A puzzle for the field is understanding how slowly accumulating and more tonic-like physiological signals are integrated to tune the brief and tightly time-locked phasic dopamine responses to environmental stimuli.