The Projection · from Anthony's Fire

A fly, heard and never rebuilt

This is the real male fruit fly: every traced neuron in the MaleCNS connectome, placed where its cell body sits. Scroll, and it is eaten, projected onto its own eigenvectors, collapsed into a spectrum, and played.

Loading about three megabytes of fly…

I · the host

One hundred and sixty thousand cells

Each point is a neuron. Where the dataset records a cell body, the point sits there. The optic lobes are the two great wings of light; the ventral nerve cord trails away beneath.

II · the axis

The graph finds its own axis

Colour now shows the Fiedler vector: the second eigenvector of the graph's Laplacian, computed from connections alone. Nobody told it where anything is.

III · the parasite

It enters through taste

Seeded in the gustatory neurons, it appropriates along the fly's own connections. Where it has fed, the fly is amber; where the host is used up, it is dead.

IV · the projection

Out of the body, into the eigenvectors

Every neuron leaves its place in the head and moves to its coordinates on the graph's second, third and fourth eigenvectors. Anatomy is discarded. Only relation is kept.

V · subtraction

The parasite is taken out first

Its nodes, the edges that touched them, and the record of which they were. What remains is the fly alone.

VI · the spectrum

Shape becomes number

Each neuron falls into the column of the mode it belongs to most. The columns stand at the eigenvalues. This is the form that can be heard: the spectrum is invariant to labelling, and different graphs can share one, so it can never be turned back into a fly.

VII · the waves

The lowest eigenvalues of the fly's graph, mapped to pitch. Start with the fly alone, then add the parasite, then its anti-sound. The top trace is the pressure wave and the bottom one is the spectrum you are hearing. Put headphones on if you can; laptop speakers lose the lowest partials.

wave spectrum

Nothing is playing.

“Dude, that's like fly Jesus: the only fly to live without sin.” — Meow-Ludo, on learning that the real fly was being turned into a spectrum

What is what

A picture of a connectome can make any claim look true, so here is exactly what each layer is.

layerstatusdetail
neurons, synapsesobservedMaleCNS v1.0, neurons with status Traced, body-to-body synapse counts at minimum confidence 0.5.
positionsobserved, partly estimatedAnnotated soma locations. Traced neurons with no soma annotation are placed at the mean of their neighbours.
axis, embedding, spectrumcomputedThe largest connected component, taken as an undirected graph weighted by synapse count. Its normalised Laplacian and bottom eigenpairs, from ARPACK.
parasitemodelled, illustrativeAn appropriation rule we chose. It spreads along outgoing connections and consumes the host's resource. It models nothing about flies, ergot, or activity.
joint spectrumcomputed from the modelOne parasite node per infected neuron, fed by its host, joined along the host's own edges. The fly's graph plus those nodes, re-solved.
soundartistic mappingEigenvalues to frequencies on a log scale across four octaves; amplitude falls with mode number. The chorus snaps each to a partial of 55 Hz. Harmony is the instrument's, not the fly's.
activitynoneNo neural activity is simulated anywhere on this page. Nothing here is the fly thinking.