A Cambridge-led team produced the first full-scale connectome of a male adult Drosophila brain and ventral nerve cord, detailing about 166,700 neurons and millions of connections.

Researchers completed a comprehensive map of all 124 million neural connections in the male fruit fly brain, building on a female connectome from two years earlier to compare wiring across sexes.

HHMI Janelia Research Campus and collaborators published the wiring diagram of the full central nervous system of an adult male fruit fly, encompassing the brain and ventral nerve cord with millions of connections.

While not explaining human sex differences, the findings may illuminate how genetic differences shape brain wiring and behavior in humans, with potential relevance to autism and schizophrenia.

The researchers frame a broader goal of uncovering general principles by which genetic differences influence brain wiring and behavior across species.

The study aims to understand how genetic differences shape brain wiring and behavior, with possible implications for human conditions linked to neural wiring differences.

The study identifies specific brain circuits linked to male courtship, aggression, and love-song production, showing wiring differences that enhance visual tracking, aggression circuits, and wing-sound pathways.

Key behavioral circuits include enhanced visual tracking for courtship, stronger aggression-related wiring, and a distinct wing-song circuit essential for male courtship songs.

Beyond biology, the work could inform improvements in AI by drawing inspiration from biological wiring patterns for more efficient networks.

Three companion studies apply the male fly map to visuals, taste, and social behavior, illustrating the map’s broad research utility.

The next phase focuses on applying fly connectome lessons to vertebrate models to explain how brains generate behavior and to shed light on neurological conditions like Alzheimer’s, autism, and depression.

The project demonstrates how neural wiring underpins transforming sensory input into behavior and how sex differences in wiring drive divergent behaviors.