Basolateral amygdala dopamine transmits a nonassociative emotional salience signal

Adaptive decision making relies on proper disambiguation of upcoming positive and negative events. The basolateral amygdala (BLA) is central to this, assigning emotional value to stimuli to facilitate appropriate behavior. The ventral tegmental area (VTA), which is classically known to regulate associative learning and incentive motivation via dopamine projections to the striatum, also contains strong dopamine projections to the BLA, but this system has received much less attention. Here, we investigated how in vivo BLA dopamine signaling is engaged during valenced experiences in associative learning. First, we show that BLA dopamine signals scale with intensity of aversive stimuli, but not reward value, and reward-predictive cues evoke BLA dopamine signals that diminish, rather than grow, with training. As the complexity of the learning context was increased, where rats actively differentiated between various cue types signaling threat, reward, safety, and neutral associations, the magnitude of cue-evoked BLA dopamine re-scaled to report the level of relative emotional saliency. Fear and safety cues prompted larger, more sustained dopamine signals compared to reward and neutral cues. Despite these distinctions, cue-evoked dopamine signals did not reliably correlate with behavioral expression, and optogenetically enhancing BLA dopamine did not alter freezing behavior. Together, these results indicate that dopamine signaling in the BLA encodes the emotional weight of sensory transitions, but not the associative strength or value of conditioned cues. Our findings broaden the theoretical landscape of dopamine heterogeneity, showing that BLA dopamine contributes to tagging affective states, in support of dynamic discernment of relative stimulus importance during learning.