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# Complete wiring map of the male fruit fly nervous system: 166,000 neurons, 125 million synapses
- URL: https://globalfeed.ai/en/complete-wiring-map-of-the-male-fruit-fly-nervous-system-166-000-neurons-125-million-synapses/
- Published: 2026-09-04T09:28:36.000Z
- Updated: 2026-09-04T09:28:36.000Z
- Description: Google Research and HHMI Janelia published the full connectome of the male fruit fly brain and central nervous system in Cell, the largest brain map by neuron count so far.
- Author: GlobalFeed Editor
- Tags: Google Research, connectomics, neuroscience, x-GoogleResearch, x-HHMIJanelia, dil-en, denetim-gerekli, video, x-gitti

Google Research, in a project led by the HHMI Janelia Research Campus, has released a complete wiring diagram of the male fruit fly (*Drosophila melanogaster*) brain and central nervous system. The map covers more than 166,000 neurons and 125 million synaptic connections, making it the largest brain map to date by number of neurons.

The paper appeared in **Cell** under the title "Sexual dimorphism in the complete connectome of the *Drosophila* male central nervous system" and caps a decade-long collaboration. Michał Januszewski and Viren Jain of Google Research announced the work.

## From brain to body

Besides the central brain and optic lobes, the map includes the ventral nerve cord, the fly's analogue of a spinal cord. That makes it possible to link auditory, visual and olfactory inputs to motor outputs. Human experts at HHMI Janelia annotated and proofread the reconstruction. The dataset can be explored and downloaded through Neuroglancer, the open-source viewer Google built for very large multidimensional data.

The female fruit fly brain and nerve cord had already been mapped. Having both sexes allows comparison in regions where neurons differ, which supports work on the biology of courtship and aggression, and reveals individual variability in regions that are alike.

## How it was built

A brain is cut into millions of thin sections, each one imaged, then stitched into 3D reconstructions using AI. The team's tools include flood-filling networks, which start at a single pixel and identify every other pixel belonging to the same object. Google's Connectomics team released a fully automated reconstruction of a female fly brain in 2019, and in 2020 a human-verified half-brain map with 25,000 neurons and 21 million connections. A recent effort added synthetic neurons to the training data, improving the speed and accuracy of the PATHFINDER reconstruction system.

The field is moving into vertebrates. In a Columbia University-led study in **Nature**, the team helped map part of the elephantnose fish hindbrain used for signal processing. Mapping the 86 billion neurons of a human brain is not yet possible.

Details in the [Google Research post](https://goo.gle/4qQTtIW?ref=globalfeed.ai).