Sensitive dLight3 for imaging broad-spectrum dopamine events across brain regions

Dopaminergic neurons modulate movement, motivation, and learning by dynamically regulating dopamine release across distributed neural circuits. However, existing genetically encoded dopamine sensors lack the sensitivity and resolution to capture the full amplitude and temporal complexity of in vivo dopamine signaling, limiting insight into its functions across behavioral contexts. Here, we present dLight3.8, a fluorescence-intensity and lifetime-based sensor with a substantially expanded dynamic range compared to existing dopamine sensors, enabling transformative detection and differentiation of dopamine release across brain regions and behaviors. Specifically, the enhanced sensitivity of dLight3.8 permits robust, single-trial recording of dopamine release spanning a wide concentration range in response to electrical, optogenetic, and behavioral stimuli, in multiple species and circuits. Using dLight3.8, we uncover a region-specific, gradual shift in dopamine encoding across motor learning, from tracking lick timing to signaling reward prediction. Our findings demonstrate that dLigth3.8 provides quantitatively reliable, highly sensitive measurements of graded dopamine release, which is essential for elucidating diverse roles of dopamine signaling in shaping animal behavior.