PPL101 (1pedc) DANs (green) have a dual function in appetitive motivation and reinforcement of aversive learning, with shock and bitter taste. Tonic dopamine release from PPL101 DANs suppresses the odor-driven excitability of the GABAergic approach-directing mushroom body output neuron (MBON11, blue) in food-satiated flies. In hungry flies elevated dNPF relieves the PPL101-mediated suppression, which elevates odor-driven MBON11-directed approach/appetitive behavior. Phasic PPL101 activity is evoked by aversive stimuli and released dopamine writes aversive memories by depressing connections between odor-specific KCs and MBON11. This leaves other MBON outputs, such as avoidance-favoring MBON01 (orange) to direct conditioned odor avoidance behavior. PPL101 input SEZON01 neurons are required for aversive learning reinforced by shock and bitter taste, and SEZON01 are subject to OA-directed modulation from hunger-responsive AKHR neurons that respond to circulatory AKH even in the satiated condition.
