Dual-channel whole-brain imaging reveals distinct dopamine and calcium dynamics in walking Drosophila

Simultaneous recording of intra- and extracellular neuronal signals across the brain during behavior is crucial for unraveling brain information processing. In Drosophila, large-scale recordings have been explored, yet simultaneous dual-channel whole-brain imaging remains a significant challenge. We developed a system combining a Fourier light-field microscope with dual-focal microlens arrays optimized for adult walking flies, extending imaging volume while maintaining resolution requirements. This optical system is further combined with a cross-modal 3D registration and segmentation pipeline to integrate functional and structural data. Using this system, we simultaneously measured brain-wide intracellular calcium activity and extracellular dopamine release during locomotion. We found that functional maps and neural dynamics for dopamine and calcium are distinct across the brain and within specific compartments, particularly in the mushroom body and central complex, aligning with their anatomical bases. Both calcium and dopamine representations of locomotion are distributed, yet they exhibit different patterns. Mushroom body compartments can be functionally categorized into two types based on their responses to specific locomotive actions. Forward walking or acceleration boosts activity in compartments innervated by PAM dopaminergic neurons, while dampening activity in those targeted by PPL1 dopaminergic neurons. Conversely, backward walking or deceleration heightens PPL1 activity while reducing PAM activity, consistent with the functions of these neurons in encoding approach and avoidance choices. Notably, single-compartment activity can reliably decode behavior choices. Our findings, spanning whole-brain, brain-region, and single-compartment, demonstrate the capability of our system to uncover neural dynamics across multiple scales and channels in behaving animals.