A fly body steered by real fly-brain wiring

Every decision the fly makes on the plate comes from spiking neurons wired exactly as they are in a mapped fruit fly brain. Nothing tells it to walk to sugar, refuse bitter, groom or flee.

The brain

Wiring: the FlyWire connectome of an adult female brain (138,639 neurons, 15.1 million connections), reconstructed from electron microscope images taken at Janelia.
Running live in this page: the 6,407 neurons and 560,155 connections that take part in these behaviours. In full-brain runs of the same stimuli, every other neuron stayed silent, so leaving them out changes little: outputs of the live circuit and the full 138,639-neuron brain agree at r = 0.998 (average gap 1.3 Hz).
Neuron model: leaky integrate-and-fire with the published parameters of Shiu et al. (Nature, 2024). Connection strength is synapse count, sign is the predicted transmitter.
This is not Janelia's newer 166,000-neuron male brain and nerve cord. That dataset could not be downloaded in the session that built this page.

World in, behaviour out

Small object seen	LC10 visual neurons of that eye	DNa02, DNg13 turn toward it; oDN1, BDN2 walk
Sugar under it	sweet taste neurons	MN9 extends the proboscis
Bitter under it	bitter taste neurons	MN9 stays silent, even with sugar
Dust on antennae	Johnston's organ C/E neurons	aDN1, aDN2 start antennal grooming
Looming swatter	LPLC2, LC4 loom detectors	giant fiber fires: jump and fly
Object in its face	LC16 visual neurons	moonwalker neurons (MDN) walk it backward

What is scripted, not neural

The senses: I chose which sensory neurons fire, and how fast, for each event in the world. The eyes are not simulated photoreceptor by photoreceptor.
The body: legs, wings and the flight path are animation. The leg and wing circuits live in the nerve cord, which this dataset lacks. Body rules that are mine: legs hold still while it feeds or grooms, escape take-off happens when the giant fibers pass 120 Hz, and walking speed and turn rate scale with the firing rates shown.
Everyday flight: the fly takes off on a timer after a few idle seconds and lands on a timer or when a seen object is close. Those triggers are scripted. In the air it still steers with the same turn neurons, so it banks toward objects it sees.
The slab is solid and hides whatever is behind it, so the fly loses sight of its target and the LC16 pathway backs it away.

Known limits

No smell. Odour input drives this model into runaway, seizure-like firing, so it is left out.
No spontaneous activity, memory or learning. With nothing to sense the brain is silent, and the fly will go back to a bitter drop it already rejected.
The wiring responds more strongly to the left eye than the right, so approaches curve.