Dissociable dopamine dynamics for learning and motivation

Abstract

The dopamine projection from ventral tegmental area (VTA) to nucleus accumbens (NAc) is critical for motivation to work for rewards, and reward-driven learning. How dopamine supports both functions is unclear. Dopamine spiking can encode prediction errors, vital learning signals in computational theories of adaptive behavior. By contrast, dopamine release ramps up as animals approach rewards, mirroring reward expectation. This mismatch might reflect differences in behavioral tasks, slower changes in dopamine cell spiking, or spike-independent modulation of dopamine release. Here we compare spiking of identified VTA dopamine cells with NAc dopamine release in the same decision-making task. Cues indicating upcoming reward increased both spiking and release. Yet NAc core dopamine release also covaried with dynamically-evolving reward expectations, without corresponding changes in VTA dopamine cell spiking. Our results suggest a fundamental difference in how dopamine release is regulated to achieve distinct functions: broadcast burst signals promote learning, while local control drives motivation.