MUSCA

About this thing

MUSCA is a live, in-browser map of the complete central nervous system of a male Drosophila melanogaster — 166,700 neurons joined by 124 million synapses, reconstructed from electron microscopy by HHMI Janelia, Google Research and collaborators and released as male-cns:v1.0.

What you can do

• Atlas — fly around the real wiring diagram. Every dot is a neuron at its real soma coordinate; the haze is a 1.1-million-point sample of real synapse locations.
• Poke — drop a spike into a single cell and watch it propagate across real synapses. The wave respects real connection weights, so it goes lumpy, stalls, and jumps — exactly where the anatomy says it should.
• Reverse — pick a behaviour. The app searches the connectome backwards for the strongest anatomical path from sensory cells to the motor neurons that execute it.
• Lesion — silence a cell type and measure how much of the brain you just cut off.

Where the numbers come from

• Soma coordinates, cell types, classes, sides, dimorphism flags — MaleCNS v1.0 body-annotations.
• Connection weights — MaleCNS v1.0 connectome-weights (segment-to-segment synaptic counts, min confidence 0.5). The 25.6 M connections among annotated neurons are pruned for legibility: edges below 6 synapses are dropped, and each neuron keeps only its 24 strongest outputs, leaving 2.8 M edges drawn here.
• Synapse cloud — a 26-row-group sample of MaleCNS v1.0 syn-points.
• Transmitters — MaleCNS v1.0 aggregate neurotransmitter predictions.

Caveats — read these

The cascade is a toy model. Real neurons have ion channels, inhibition, delays and adaptation; here activity is just a decaying, weight-scaled diffusion across an anatomical graph. It shows you where a signal can go, not what the fly actually computes. The "reverse" paths are the strongest anatomical routes, not verified physiological circuits. Nothing here is a claim about behaviour — it is a way to see the shape of a brain.

Dorkenwald, S., Matsliah, A., Sterling, A.R. et al. Sexual dimorphism in the complete connectome of the Drosophila male central nervous system. Cell (2026). · Data: male-cns:v1.0, Janelia FlyEM, CC-BY 4.0.

Built as an independent visualisation. Not affiliated with Janelia, Google or the authors.

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