Converging dopamine pathways onto basolateral amygdala neurons encode exploration decisions

Exploration is a fundamental innate behavior essential for securing survival-necessary resources, but it also increases risks. However, the neural mechanisms encoding exploration decisions remain unknown. Here, we show that social companionship motivates both innate-driven and experience-dependent explorations in mice. Dopaminergic neurons in the ventral tegmental area (VTA^DA neurons) determine exploration decisions by encoding risky vigilance (via phasic firing) and exploration motivation (via tonic firing). Two subpopulations of VTA^DA neurons co-innervate the same population of basolateral amygdala neurons via direct and indirect pathways. Tonic firing-biased DA-D2R transmission in the medial prefrontal cortex (indirect pathway) mediates exploratory behaviors, which are reinforced by social interactions, while phasic firing-biased DA-D1R transmission in the direct pathway mediates avoidant behaviors. The dynamic balance between these two competing DA pathways coordinately encodes exploration decisions. These findings establish the VTA^DA neuron as a central hub and the circuit integration of biased DA transmission as a central mechanism encoding exploration decisions.