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Holy sh*t. Look what I did with this fly!
A couple of days ago Odyssey posted a clip: a fruit-fly brain flying around inside their AI world. No paper, no code. So I went to see what’s actually going on inside a fly’s head.
Scientists sliced a fruit-fly brain into thousands of layers and traced every connection by hand. The result is a map of 127,400 neurons and ~50 million synapses. Built on that map is an open-source brain model (Nature, 2024): each neuron is simple, but they’re wired exactly like a real fly’s.
I took that model and gave the fly sugar:
> Sugar touches the proboscis, and taste receptors fire first.
> The signal spreads through the brain, and 27 ms later MN9 switches on. That’s the neuron that moves the proboscis, the “eat” command.
> In a full second only 391 neurons fire. That’s 0.3% of the brain. The rest doesn’t care about sugar.
> Weaker sugar? The decision comes 12 ms later: 39 ms instead of 27.
> The strongest route to “eat” is just three hops: receptor → interneuron → descending neuron → MN9.
Here’s the wild part. A three-line script, “if sugar: eat”, looks exactly the same from the outside. A video can’t tell you whether a fly has a brain.
In Eon’s stack, which Odyssey’s clip likely builds on, vision is still “somewhat decorative” and barely drives behavior. Yet Odyssey’s world is almost pure vision for the fly. So what’s steering their fly? They haven’t said.
