Male fruit fly brain connectome completed with 150,000 neurons mapped

Researchers completed the first full 3D map of a male fruit fly brain's neural circuitry, identifying 150,000 neurons and 300 million synaptic connections.

Researchers from Howard Hughes Medical Institute's Janelia Research Campus and Google completed the first full three-dimensional map of a male fruit fly brain's neural circuitry. The mapping identified 150,000 neurons and 300 million synaptic connections within the nervous system, representing the second fruit fly connectome (the female version was completed earlier in 2026). The project took four years to validate from initial brain preparation to final connectome analysis, using generative AI models to stitch tissue slices and identify synaptic connections. Human proofreaders iteratively refined synapse recognition accuracy during the process.

This work advances foundational neuroscience by providing a scalable model for understanding neural circuitry. Fruit flies share core neural mechanisms with humans, so this connectome could accelerate research into neurodevelopmental disorders and brain-computer interfaces by offering a simpler, cheaper reference point for circuit analysis.

The achievement moves potential medical abundance by reducing the cost and time to model complex neural pathways. As fruit fly brains are small and well-studied, this connectome could lower research expenses for neurotech applications, making early-stage brain disorder interventions more accessible. Future work will likely focus on integrating this model with human neural data to identify cross-species circuit principles.

Caveats: The neuron count refers only to the nervous system, not the entire brain. The 300 million synapses represent neural connections, not the full nervous system. The female connectome was completed earlier in 2026 but this report focuses on the male version. No single institution owns the work—this was a collaboration between biological and computational teams.

Source: Ars Technica