A drop on the tongue
Grab the droplet and hold it against the labellum. While it touches, twenty sugar-sensing neurons (the cells Shiu et al. drove in their model) or 65 bitter-sensing ones fire; pull it away and they stop. If MN9, the proboscis motor neuron, fires, the proboscis extends and reaches for the drop. Nothing is scripted: the extension is MN9's firing rate, frame by frame.
sugar/water GRNs · 20 cells, labellum
CB0700, CB0248, CB4055… · gnathal interneurons
MN9 (CB0701) · 2 proboscis motor neurons
Something looms
Grab the shadow and rush it at an eye. Each eye sees the disc's angular size; LPLC2 and LC4 looming detectors fire in proportion to how fast it expands, and only on the eye that faces it. They converge on the two giant fibre neurons; one giant fibre spike and the fly jumps. Hold the disc still and nothing happens, however close it is.
LPLC2 + LC4 · 314 visual projection neurons
PVLP111, PVLP011… · lobula-plate interneurons
DNp01, the giant fibre · 2 descending neurons
A brush on the antenna
Drag the brush onto an antenna. Contact fires that antenna's bristle neurons (BM_Ant); sweeping the brush across them fires them harder and deflects Johnston's organ too. In the model the bristle neurons reach the antennal motor neurons in a few synapses, and the antenna moves. Grooming-related descending neurons (DNg15, DNg84, DNg35) light up as well.
BM_Ant · 41 bristle neurons · JO-C/E · 433 Johnston's organ neurons
DNg15, DNg84, DNg35 · grooming-related descending neurons
CB0810, CB0873 · 10 antennal motor neurons
The world turns
Grab the striped drum and spin it; it coasts with inertia. On each eye, T4 and T5 cells tuned to that direction fire in proportion to the drum's speed. They drive the HS and VS wide-field cells and, downstream, the neck motor neurons. The head turns with the drum, an optomotor response whose size is the left-right difference in those motor neurons.
drum: still · arrow keys nudge it
T4a/T5a, T4b/T5b · 800 direction-selective cells per eye
HSE, HSN, HSS, VS1–8 · lobula plate tangential cells
CB0705, CB0706, CB0918… · 26 neck motor neurons