Fly Compass — a ring attractor from the real wiring

The ring — where the fly thinks it is facing

outer band: EPG compass cells (the bump = heading) inner band: Delta7 inhibition (lights up opposite the bump) needle: population vector of EPG firing

Click anywhere on the ring to drop a landmark there (the visual system's job) — the bump jumps to it and stays anchored while the landmark is in view. Hold a turn button, drag the slider, or use ← →: the landmark is gone and the bump slides round. Let go: it stays — held by nothing but the wiring, and in the dark it drifts slowly toward this fly's favourite headings, as a real fly's compass drifts in darkness. Nothing is stored anywhere — no weight changes, no variable holds "heading". The geometry of the wiring holds it.

Controls

Heading

—°

Bump strength

—%

Turn command

0.00

Turn (springs back to centre when released)

Neurons (EPG / PEN / PEG / Delta7)—

Synaptic connections between them—

Mean EPG firing (spikes / step)—

Bump re-formed spontaneously0 times

Sim step rate—

What is real: every neuron, its transmitter, and every one of the synapse counts between them come straight from the connectome. The ring order was derived from the wiring (a spectral embedding of the EPG→PEN→EPG loop) and only afterwards checked against the anatomists' glomerulus labels: it matched, 18 for 18.
What is tuned: two global gains (excitatory, inhibitory) and two tonic currents, because synapse counts are not synaptic strengths.
What it cannot do: learn. The wiring is frozen. "Kill the bump" wipes every voltage — and a new bump forms anyway, at a random heading, exactly as it does in a real fly in the dark.

The brain in 3D — the same 152 cells, their real shapes, lit by the simulation

EPG PEN, left bridge PEN, right bridge PEG Delta7 loading skeletons… brightness

These are the reconstructed skeletons of the actual neurons in the simulation, from the same release as the wiring — every arbor is where it was in the animal. A cell flares when it fires. The doughnut is the ellipsoid body, the ring the bump lives on; the arch above it is the protocerebral bridge. Drag to turn it, scroll to zoom; it drifts on its own when left alone. Turn the compass and watch the bump walk round the real ring.

Fly Compass — a ring attractor running on the real wiring

The ring — where the fly thinks it is facing

Controls

The brain in 3D — the same 152 cells, their real shapes, lit by the simulation

Spike raster — EPG rows sorted by ring position, so a turn shows as a diagonal streak