Connectome analysis reveals brain-wide visual processing in Drosophila

Abstract Sensory processing relies on an intricate interplay between specialized sensory circuits and the broader brain. Leveraging the whole-brain Drosophila melanogaster connectome, we analyzed long-range projections linking the optic lobe (OL)—the principal visual center—reciprocally with the central brain and the contralateral OL to determine how visual features are computed by a brainwide network. By quantifying synaptic polarity and connectivity, we classified the projection neurons into feedforward, feedback, and bilateral groups. Feedforward neurons form an information bottleneck, consolidating diverse visual features from the OL and distributing them through modular pathways for higher-order processing. Feedback neurons densely innervate OL structures, conveying contextual signals in the central brain via precise recurrent loops. Bilateral neurons link local visual circuits across the two OLs, providing a substrate for inter-ocular processing. These findings reveal how early visual pathways interface with brainwide circuits to support diverse brain functions and enable context-dependent flexibility in sensory computation. Highlights Whole-brain connectome analysis identifies three streams of brainwide visual processing Feedforward neurons form a bottleneck and distribute features for higher processing Feedback neurons modulate early vision via layer-specific recurrent loops Bilateral neurons bridge both optic lobes to enable inter-ocular processing