This study investigates the relationship between dopamine (DA) transients and reward time horizons in different striatal subregions of rats. The authors found that DA dynamics, including the tempo of spontaneous fluctuations, the temporal integration of prior rewards, and the discounting of future rewards, systematically accelerate from the ventral to the dorsomedial to the dorsolateral striatum. These differences in DA dynamics are linked to distinct time horizons for evaluating rewards, which enable animals to make adaptive decisions across a wide range of behavioral timescales. The study also examines how these time horizons affect reward prediction errors (RPEs) and learning processes, providing insights into the hierarchical structure of reinforcement learning in the brain. The findings suggest that the striatum's gradient of reward time horizons supports efficient learning and adaptive motivation in complex behaviors.This study investigates the relationship between dopamine (DA) transients and reward time horizons in different striatal subregions of rats. The authors found that DA dynamics, including the tempo of spontaneous fluctuations, the temporal integration of prior rewards, and the discounting of future rewards, systematically accelerate from the ventral to the dorsomedial to the dorsolateral striatum. These differences in DA dynamics are linked to distinct time horizons for evaluating rewards, which enable animals to make adaptive decisions across a wide range of behavioral timescales. The study also examines how these time horizons affect reward prediction errors (RPEs) and learning processes, providing insights into the hierarchical structure of reinforcement learning in the brain. The findings suggest that the striatum's gradient of reward time horizons supports efficient learning and adaptive motivation in complex behaviors.