A fruit fly’s tiny nervous system is becoming an unusually detailed guide to how brains work. On September 3, 2026, a collaboration led by HHMI Janelia published a male fly connectome spanning the brain and ventral nerve cord: more than 166,000 neurons, mapped to help trace how sensation becomes movement. Research team’s report.
Tracing the Wiring
A connectome records neurons and their connections. Building one combines electron microscopy, AI-assisted reconstruction and extensive human proofreading. The earlier 2024 FlyWire female brain map reconstructed 139,255 neurons and 54.5 million chemical synapses between them. Its companion atlas names cell types so researchers can navigate the network. These are separate specimens and datasets, not successive counts of the same brain. Wiring diagram · Cell atlas.
Testing How a Brain Works
Shiu and colleagues used FlyWire connectivity and predicted neurotransmitters to build a simplified model of neural activity. It generated predictions about feeding and grooming circuits that the team tested in biological experiments. Researchers can use this approach to identify candidate neurons, predict what happens when they are activated or silenced, and check the result in a fly. Computational study.
The Limits of a Digital Fly
A wiring map does not capture every aspect of a living brain. Eon’s March 2026 virtual-fly demonstration combined simplified neurons with trained movement controllers and some hand-chosen interfaces; learning and internal state were largely missing. Its technical report makes those limits explicit. The opportunity is to turn increasingly complete maps into better experiments—and test which features of brain wiring explain behavior.
Sources checked September 14, 2026.