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.