MaleCNS Connectome
#32 in Research & Science
« The first complete map of the brain and nervous system of a male fruit fly, featuring more than 166,000 neurons and 125 million connections, freely explorable online »
Verified Tool
MaleCNS Connectome: a complete male fruit fly nervous system anyone can explore
MaleCNS Connectome is the complete map of a male fruit fly's central nervous system, from brain to ventral nerve cord, neuron by neuron. HHMI Janelia, the University of Cambridge, the MRC LMB and Google Research published it in Cell in September 2026, logging 166,700 neurons and 125 million synapses, the largest brain map to date. Everything is free to browse in 3D from a regular web browser, and the full dataset downloads under an open license.
Pros
- Largest brain map ever published, by neuron count
- Free 3D browsing straight from the browser
- Full dataset downloadable under a CC-BY license
- Brain and nerve cord joined with an intact neck
- Male-female comparison down to single synapses
Cons
- Built first for researchers, with a technical learning curve
- A static wiring map, no live neural activity
- Documentation aimed at an academic audience
Seven microscopes and 44 person-years behind MaleCNS
The MaleCNS dataset covers 166,700 neurons, 125 million synapses and 11,710 cell types, reconstructed from a single male fly. Seven electron microscopes imaged the animal for thirteen months at 8-nanometer resolution, producing a 160-teravoxel volume.
Google's AI then segmented every cell, and Janelia annotators proofread the whole thing by hand, an effort estimated at 44 person-years. The result joins the short list of finished connectomes, and it is the first fully verified one to join brain and nerve cord through an intact neck, from eyes to legs.
Janelia's walkthrough of the finished fly connectome
Male versus female, a first synapse-level comparison
Every fly brain mapped before this one came from a female, including the FlyWire map released in 2024. With this first male brain, researchers can finally compare both sexes of an animal with complex social behavior.
The numbers tell a sharp story. Across cross-matched cell types, 8,069 are identical between sexes, 138 are wired differently, 289 exist only in males and 71 only in females. Those cells cluster in higher brain centers, where courtship and aggression get decided.
Google already names the zebrafish and a piece of mouse brain as the next targets, plenty of fuel for AI-assisted scientific research in the years ahead.
Neuroglancer, neuPrint, Python, how to explore MaleCNS
Access to MaleCNS is free end to end, and the data ships under a CC-BY license. You type a neuron name into Neuroglancer and its 3D reconstruction appears, synapses included (give the page a few seconds, the meshes are heavy).
The internet adopted it in its own way. Within days of publication, developers wired simulations of the connectome to Doom, Super Mario 64 and Minecraft, racking up millions of views.
| Tool | What it does |
|---|---|
| Neuroglancer | 3D view of images, neurons and synapses |
| neuPrint | Connectivity queries, free account required |
| Cell Type Explorer | Browse the 11,710 cell types |
| neuprint-python and malecns (R) | Programmatic data analysis |
Frequently asked questions
Is the MaleCNS connectome free?
Yes, completely. Browsing through Neuroglancer does not even require an account, and the entire dataset downloads at no cost. Research institutions including HHMI, the Wellcome Trust and the MRC funded the project, so there is no subscription anywhere. Only neuPrint asks for a free account before you run connectivity queries.
What is the difference between MaleCNS and FlyWire?
FlyWire maps the brain of a female fly, released in 2024 with roughly 140,000 neurons but no nerve cord. MaleCNS charts an entire male, neck included, so a full circuit can be traced from eyes to legs and both sexes compared synapse by synapse. The two datasets actually work well side by side.
Is the simulated fly playing Doom conscious?
No. The connectome records fixed wiring, with none of the biochemistry or electrical activity of a living brain. Viral videos run simplified computational rules on top of the map, and nothing in them points to conscious perception. No living insect takes part in those gaming sessions.
Can MaleCNS data be used in a commercial project?
Under the CC-BY license, yes, commercial use included, as long as you credit the FlyEM Project Team, the Cambridge Connectomics Group and Google Research. That legal openness is what made the wave of simulations, games and derivative tools possible within days of release.
Verdict: Neuroscience labs gain a reference dataset that took a decade to assemble, free of charge. Teachers, data tinkerers and simulation hobbyists get the most detailed brain publicly available on the web to experiment with.
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