🧠 The dataset: MCNS
On 3 September 2026 a consortium led by HHMI Janelia, with the
MRC Laboratory of Molecular Biology and Google Research, published the first complete
connectome of an entire adult male Drosophila central nervous system — central brain,
both optic lobes and the ventral nerve cord, joined by an intact neck connective.
166,000+ neurons and 125 million synaptic connections — the largest brain map by neuron
count to date. It was proofread and annotated by human experts and is publicly viewable, explorable
and downloadable.
⚡ The escape reflex
Flies survive because of a dedicated, extremely fast escape pathway. Looming-sensitive visual
neurons (LC4 / LPLC2) detect an expanding dark object — a swatter, a hand, a dart — and drive
descending neurons that command the giant fibre, which fires the flight and leg muscles in
a single decisive burst.
That's the circuit this game simulates, live, at 1 ms resolution. When the pink GF node fires,
the fly physically commits to a dodge — the spike is the movement.
🪰 Why it eventually stops dodging
Real flies habituate: wave your hand repeatedly without hitting it and the escape response
weakens. The simulation reproduces this with synaptic depression and a hard-adapting giant fibre —
repeated whiffs raise the trigger threshold and soften the dodge.
So the winning strategy is real neuroscience: bait the reflex, let it fatigue, then strike.
A hit re-sensitises it, so don't waste your opening.
🔬 Male vs female
Because a female CNS connectome already existed, MCNS enables the first synaptic-resolution
comparison across sexes of an adult animal with complex behaviour: 262 sex-specific and
114 sexually dimorphic cell types (4.8% of the central brain). Around 100 male-specific
interneuron types coordinate most male-specific behaviours.
Three companion papers use the map to dissect the fly's visual system, taste system and social
behaviour.
Honesty note: the arena's fly is not running the full 166,000-neuron connectome in your
browser. It runs a compact, re-seeded LIF network that mirrors the published escape pathway's logic.
The numbers in the hero are the real published figures and link below.