Breaking

Janelia and Google publish MaleCNS, then developers try to teach the fly brain Doom

September 13, 2026 at 15:16 EDT

Research & Papers
Open Source

HHMI Janelia, Google Research and collaborators have released MaleCNS v1.0, a complete wiring diagram of an adult male fruit fly’s brain and ventral nerve cord, and developers have already plugged that public map into games — prompting a debate over whether anyone is really teaching a fly, or only training software around a frozen circuit.

3 September 2026 · HHMI Janelia / Google Research

The fly is mapped. The demos are not the fly.

MaleCNS v1.0 is a public wiring diagram of 166,700 neurons. Viral ‘teach the fly’ clips usually freeze that graph and train an encoder or readout around it.

Neuron count · same unit

From hemibrain to a full male CNS

25,000

Hemibrain 2020

166,700

MaleCNS v1.0 · ~6.7×

One stacked block is the 2020 half-brain map; the taller column is the finished male central nervous system.

125M

synaptic connections (Google)

6,385

Doom attempts, still unbeaten

44 yr

human proofreading labour

<5%

male cells sex-specific or dimorphic

How a typical demo is wired

Task input

Pixels, odour or damage mapped onto named sensory cells

→

Frozen connectome

166,700 leaky integrate-and-fire cells, EM weights fixed

→

Descending neurons

Brain commands to the body, including steering and escape

→

Readout

Hand decode or a trained linear layer presses the keys

What holds up

The graph is biology. Looming-to-escape and courtship-to-steering pathways can fire from the measured wiring when those cells are stimulated.

What does not

Point neurons, failed vision in some settings, unvalidated against real-fly recordings. Game skill often lives in the wrapper. Authors call it a demo, not an emulation.

The load-bearing sentence

No learned policy inside the brain. Connectome weights stay fixed at load time. Encoders and readouts are where ‘teaching’ usually happens.

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