Dynamic Encoding of Reward Prediction Error Signals in the Pigeon Ventral Tegmental Area during Reinforcement Learning

Reward prediction errors (RPEs) guide learning by comparing expected and obtained outcomes. In mammals, ventral tegmental area (VTA) activity is closely linked to RPE-like signaling, yet how avian VTA dynamics evolve during reinforcement learning remains less well characterized. Here we recorded VTA spiking in pigeons (two females and one male) performing a cue-guided operant task in which a green cue (cue + ) predicted reward contingent on a key peck, whereas a red cue (cue − ) was unrewarded. Using a 16-channel microwire array, we analyzed pooled channel-level multiunit activity (MUA) aligned to task events. Across sessions, cue + trials showed a learning-related redistribution of event-locked modulation: outcome-locked activity was more prominent early in training, while cue-locked modulation became stronger as performance stabilized, consistent with a temporal-difference–like shift of prediction-related signals. Cue − trials were sparse after early learning and showed limited cue-locked modulation in the available dataset. Together, these results provide initial evidence that pigeon VTA pooled MUA exhibits learning-related dynamics consistent with RPE-like processing and support cross-species comparisons of dopaminergic learning signals.