Google and Janelia map full fly brain with AI: 166,000 neurons, 125 million connections

alex_verem · x · 2026-09-10

HHMI's Janelia Research Campus and Google Research have completed the largest complete brain connectome ever made by neuron count: a male fruit fly's brain and nerve cord with over 166,000 neurons, 125 million connections, sorted into 11,700 cell types.

How AI broke the bottleneck: The team sliced the brain into sections thinner than a human hair and shot millions of electron microscopy images. AI models traced each neuron across slices, rebuilt 3D shapes, and mapped synaptic links; human experts verified the output. The first complete wiring diagram of any animal — a worm with 302 neurons — took over a decade of hand tracing.

Early results: One fully traced pathway runs from the eye through a male-specific "love spot" neuron to the motor neuron firing during courtship. With an existing female map, scientists can now compare complete male and female brains for the first time; three companion studies cover vision, taste, and social behavior. Full vertebrate brains are next.

Related event: Google and HHMI Release Complete Male Fruit Fly Brain Connectome(7 posts)→

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