4,871 neurons of recorded fruit-fly wiring are running live in this page, one
tenth of a millisecond at a time. When the cartoon fly walks into the sugar cube, its foreleg
touch neurons fire into that wiring. Whether it backs away is decided by four
“moonwalker” neurons (MDN) at the far end.
Try thisCut the wiring onto MDN. The touch neurons still fire and
most of the network still lights up, but the four MDN cells go dark, and the fly only
gives up and turns away when a timer runs out. That difference is the wiring’s doing.
02What is real here
and what is ours
From the connectome
The wiring
Which neuron connects to which, and how many synapses: FlyEM’s Male CNS v1.0 reconstruction of one male fly.
Excitatory or inhibitory, from each neuron’s predicted transmitter.
Cell-body positions in the picture (except 333 leg sensory neurons, whose bodies sit in the legs; those are drawn near the foreleg nerve).
Our assumptions
The simplifications
Every neuron is the same simple leaky integrate-and-fire unit (Shiu et al. 2024 settings).
“Touching” means 150 Hz random input to 288 foreleg bristle neurons.
The 8 Hz threshold, the 0.8 s minimum back-up, the turn away and the whole cartoon body.
This 4,871-neuron copy was cut out of the 211,577-neuron brain because those neurons were active under foreleg touch.
Checked
The tests
Whole brain: foreleg touch drives MDN at 16–17 Hz; zero without input; zero from hind-leg touch; beats 20 of 20 randomly rewired brains.
Under the same touch, this copy drives MDN at 14.3 Hz; the whole brain, 13.9 Hz (three runs each).
This page’s engine gives the same spikes, bit for bit, as the Python engine on a recorded input.
Known limit: held down for over a second, the copy can drift into a state where MDN falls silent.