Throw something at a brain.
This is an 834-neuron toy fly brain running the same leaky integrate-and-fire equations FlyLeno uses on all 138,639 cells. Pick a stage event. Sensory neurons start firing, the spikes travel through the network, and descending neurons decide what Leno's body does.
Spike raster 0 ms
Leno's motor output live
The crowd is quiet.
Every move Leno makes is a spike somewhere.
Nothing is scripted at the motor level. The show stimulates senses, and the connectome does the rest.
Something happens
A tomato lands, the crowd claps, a goose walks on, the music drops.
Sensory neurons fire
Poisson spikes on identified taste, smell, touch, vision and Johnston's-organ hearing cells.
15.1M connections
Signed synapse counts from FlyWire v783 carry every spike, 1.8 ms later, to its targets.
Commands leave the brain
P9/oDN1 walk, MDN back up, DNa01/02 turn, giant fiber startle, MN9 feed and talk.
Leno moves and speaks
A physics ragdoll and a phoneme voice bank turn firing rates into a very strange talk-show host.
Which neurons the show touches.
Counts are the identified FlyWire neurons each input drives and each output reads, taken from the running build.
Inputs senses
| Stage event | Neurons | Cells |
|---|---|---|
| Applause | JO-C/E/F antennal | 209 |
| Rotten tomato | LB1 bitter GRNs | 42 |
| Smells bad | Or56a geosmin ORNs | 39 |
| Sugar / snack | LB2d, LB3 sugar GRNs | 129 |
| Heckler looms | LC4 looming | 104 |
| Music, low band | JO-B 30–300 Hz | 259 |
| Music, high band | JO-A 0.3–4 kHz | 99 |
| Fruit smell, L / R | DM1–4, VA2 ORNs | 150 + 140 |
| What Leno sees | R1-6, per eye | 400 + 400 |
Outputs body & voice
| Behaviour | Neurons | Cells |
|---|---|---|
| Walk forward | P9 (DNp09, DNg97) | 4 |
| Back up | MDN moonwalker | 4 |
| Turn L / R | DNa01 / DNa02 | 2 + 2 |
| Startle | giant fiber DNp01 | 2 |
| Groom | aDN1 (DNg62) | 2 |
| Feed / talk | MN9 proboscis | 2 |
| Voice | DNg02 + DNp13 song | 27 |
| Gag / retch | pharyngeal MNs | 38 |
| Fart | oviDN | 6 |
| Reward / punish | PAM / PPL1 dopamine | 307 / 16 |
Two lines of calculus, 138,639 times.
The brain model follows Shiu et al. (2024, Nature), where the same equations on the same wiring predicted which neurons drive feeding and grooming, and experiments confirmed it.
FlyLeno integrates the model lazily. Between inputs a neuron's voltage has a closed form, so a cell is only stepped while it could reach threshold. That keeps 15 million connections running in plain JavaScript in a Web Worker.
On top of the connectome sits a small learning loop. The fly's own PAM and PPL1 dopamine neurons, driven by the crowd, gate plasticity on the synapses onto Leno's vocal motor neurons. Jokes that get applause get repeated.
A show the fly runs.
Segments
Events
The host.
