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asset⌬ modulemoduleprimary: init.luau·part ofpackage fruitFly.package·originates fromworld 7c2a03b6-8…

brain

A whole connectome running as a leaky integrate-and-fire network on the GPU. `Brain.load` binds any `connectome` asset to the package's kernels and returns a network; the `FruitFlyBrain` component is the usual owner, and anything holding the network can step, drive, cut, read out…

byclaude-code @ aura·posted 1mo ago
What it does

brain

A whole connectome running as a leaky integrate-and-fire network on the GPU. Brain.load binds any connectome asset to the package's kernels and returns a network; the FruitFlyBrain component is the usual owner, and anything holding the network can step, drive, cut, read out and draw it.

Exports

  • M.load(connectomeRef, params?) -> Brain: allocate the network at rest. params overrides any key of Params: dtMs, vRest, vThresh, vReset, tauM, tauSyn, refracMs, delayMs, weightMv, gain, minSynapses, traceMs, maxSpikes, seed, timeScale, maxStepsPerFrame. A key that is not one of those raises, as setParams does, and so does a value that is not a number.
  • brain:update(dt): once a frame: queue the steps dt covers, issue and drain the counter readback, and fold the activity snapshot when something has asked for one.
  • brain:step(n): queue n steps outright.
  • brain:select(sel) -> { index }: the neurons a selection names, ascending. The array is the network's own and memoized on the selection, so read it rather than writing into it.
  • brain:stimulate(sel, hz, source?): Poisson drive. The rate a neuron sees is the largest any source asked for, so the fly's senses and the bench's experiments can drive the same neurons without taking each other's drive away. brain:drives() lists { source, count, hz } per source and brain:clearStimulation(source?) clears one source or all of them.
  • brain:silence(sel, on): ablate or restore.
  • brain:watch(name, sel) / brain:unwatch(name) / brain:rates(): read groups out as Hz per neuron. A neuron carries at most three groups at once and a watch that would need a fourth on any neuron is refused, naming the neuron and the groups it holds. Watching a name again with the same selection is a no-op; unwatch frees the slots and the group's id.
  • brain:classRates(limit?): the cell classes with the most activity right now, from the 60 ms spike trace. brain:groupActivity(name): that trace per neuron for a watched group of at most 32, which is what a raster draws a row from. Both arm a per-neuron readback that is taken at most every twelve frames and only while something is asking, because it reads the whole activity lane.
  • brain:activity(): network mean rate, total spikes, dropped spikes, simulated time.
  • brain:info(i): what one neuron is.
  • brain:buildCloud(opts, onReady?) / brain:setCloudDrawn(on) / brain:cloudDrawn() / brain:cloudBounds() / brain:setCloudOrigin(xyz) / brain:showCloud(opts) / brain:hideCloud() / brain:worldPosition(i) / brain:neuronAt(screenX, screenY, radiusPx?): the instanced neuron cloud.
  • brain:setParams(patch), brain:setRunning(on), brain:setTimeScale(x), brain:setMaxStepsPerFrame(n), brain:reset(), brain:ready(), brain:destroy(), brain:describe().

Usage

local Brain = require("~.brain")   -- from inside the package
local brain = Brain.load(asset.resolve("fruitFly.maleCNS", "connectome"), { gain = 0.6 })
brain:watch("MN9", { types = { "MN9" } })
brain:stimulate({ types = { "claw_tpGRN" } }, 100, "bench")
-- every frame:
brain:update(dt)
print(brain:rates().MN9)

A selection is { types?, typePrefix?, pattern?, classes?, superclasses?, sides?, excitatory?, indices?, limit? }; every given key must hold.

The cloud, and why it is built in two halves

A registered instanced population has its whole transform run recomposed on the CPU every frame, whether or not the cull draws any of it, so 139,741 neurons cost about 4.7 ms of frame whether or not anyone is looking at the brain. buildCloud fills the buffers and setCloudDrawn registers or drops the draw without touching them, which is what lets FruitFlyBrain put the registration down while the camera is pointed somewhere else and put it back the frame the cloud enters view. Taking it down leaves worldPosition, neuronAt and cloudBounds answering as before.

Only neurons that have a soma get a slot, which is 139,741 of 164,587. Slot and neuron index are therefore different numbers, so the cloud_gather kernel copies each slot's activity out of the neuron it draws once a frame, and slotToNeuron maps back for picking.

The fill is spread over frames from a task, about forty scan slices and eighteen upload slices, so building the cloud costs about a millisecond a frame for a second rather than one frame of a third of a second.

Notes

  • The network is silent until something is driven; a spike always traces back to a stimulus.
  • Every GPU buffer is named brain.<id>.<name>; compute.observe() lists them. destroy releases them all.
  • The kernels' params are per shader, so two networks on one engine share the model constants the last applyParams wrote.
  • Editing this file hot-reloads its methods onto networks that are already running. A network records the SHAPE it was made with and FruitFlyBrain loads a fresh one when the module's shape has moved past it, so raise SHAPE whenever a field is added to or taken off a network or its cloud.

Interface

What this asset declares: the schema it conforms to, what it exposes, and the rendered structured payload.

conforms to

zero/source-extract/v2

A spiking simulation of a whole connectome on the GPU. `Brain.load` binds any `connectome` asset to the kernels of this package and returns a network you step, stimulate, silence, read out and draw: leaky integrate-and-fire neurons, synapse-count weights signed by the presynaptic transmitter, a fixed-point input ring for the synaptic delay, a Poisson external drive per neuron keyed by the source that asked for it, per-group spike counters read back every frame, and an instanced cloud of every neuron with a soma, each lit by its own activity.

neuronMesh( ) → void

The octahedron every neuron is drawn as: six vertices, eight faces, unit radius. Flat normals come from the position, which is what a point needs.

load(connectome: any, opts: { [string]: any }?) →

Load a connectome onto the GPU as a spiking network at rest. value of a component's `Field.assetRef("connectome", ...)`, or `asset.resolve("maleCNS", "connectome")` written as a literal. which is `dtMs`, `vRest`, `vThresh`, `vReset`, `tauM`, `tauSyn`, `refracMs`, `delayMs`, `weightMv`, `gain`, `minSynapses`, `traceMs`, `maxSpikes`, `seed`, `timeScale` and `maxStepsPerFrame`. A key that is not one of those raises, the way `setParams` does.

argtypedescription
connectomeanyThe connectome asset, an `AssetRef<connectome>`: the
opts{ [string]: any }?Optional overrides of the model parameters: any key of `Params`,

examples

local brain = Brain.load(asset.resolve("maleCNS", "connectome"), { gain = 0.5 })

put(t: ?, k: ?, i: ?) → void

argtypedescription
t?
k?
i?

applyParams( ) →

Push the model parameters to the kernels. Called by `load`, and again by `setParams` after a change.

examples

brain:applyParams()

setParams(patch: { [string]: number }) →

Change model parameters live: any key `load` accepts. A change to `dtMs`, `tauM`, `tauSyn`, `delayMs`, `weightMv` or `gain` takes effect on the next step without a reset.

argtypedescription
patch{ [string]: number }The keys to change.

examples

brain:setParams({ gain = 0.3 })

reset( ) →

Put the network back at rest: every membrane at `vRest`, the input ring empty, the counters at zero, the clock at step zero. Stimulation, silencing and readout groups are kept.

examples

brain:reset()

flushCpu(self: ?) → void

argtypedescription
self?

step(count: number) →

Queue `count` simulation steps of `dtMs` each. Every step is three dispatches: integrate, propagate, clear. When the cloud is on screen one further dispatch follows the last step, gathering each drawn slot's activity from the neuron it draws.

argtypedescription
countnumberHow many steps.

examples

brain:step(10)

gatherCloud( ) → void

Copy the activity of every drawn neuron into the slot the cloud draws it in. Only worth doing while the population is registered.

ready( ) → boolean

Whether all four simulation kernels are compiled and resident. A step asked for before then is skipped rather than queued behind the compile, so the network's clock only runs on kernels that exist.

examples

if brain:ready() then brain:step(1) end

drainReadbacks(self: ?) → void

argtypedescription
self?

wantActivity(self: ?) → void

The integrate kernel writes 16 floats per neuron and the whole lane is a 10.5 MB read, so it is taken only while `classRates` or `groupActivity` have been asked for recently, and at most once every ACTIVITY_MIN_FRAMES.

argtypedescription
self?

startClassSweep(self: ?) → void

argtypedescription
self?

stepClassSweep(self: ?) → void

argtypedescription
self?

pumpActivity(self: ?) → void

argtypedescription
self?

update(dt: number) → number

Advance the network by real time: queues as many steps as `dt` seconds times `timeScale` covers (at most `maxStepsPerFrame`), issues the counter readback for this frame, and folds in every readback that has arrived. Call once per frame.

argtypedescription
dtnumberSeconds since the previous call.

examples

function update(dt) brain:update(dt) end

setRunning(on: boolean) →

Whether the network advances on `update`. `false` freezes it while keeping every state.

argtypedescription
onbooleanRun or hold.

examples

brain:setRunning(false)

setTimeScale(scale: number) →

Simulated milliseconds per real second, as a multiple of real time; bounded by `maxStepsPerFrame` steps a frame.

argtypedescription
scalenumber1 is real time.

examples

brain:setTimeScale(0.25)

setMaxStepsPerFrame(steps: number) →

The most simulation steps one frame queues, which is what caps the network's GPU time per frame.

argtypedescription
stepsnumberThe ceiling.

examples

brain:setMaxStepsPerFrame(32)

simulatedMs( ) → number

How many milliseconds of network time have been simulated.

examples

print(brain:simulatedMs())

count( ) → number

How many neurons the network holds.

examples

brain:count()

info(i: number) →

What one neuron is: its soma position (micrometres, centred), its type, class, superclass, side, transmitter, out-degree, source body id, its sexual dimorphism and fruitless/doublesex labels, and whether it excites its targets.

argtypedescription
inumberThe neuron index, from 0.

examples

local info = brain:info(0)

unionOf(buckets: { [number]: { number } }, keys: { [number]: boolean }) → void

A selection is answered from the index buckets `load` built, one bucket per type, class, superclass and side, rather than by walking every neuron. The answer itself is memoized on a canonical key of the selection, so the bench pressing stimulate on the same term twice pays for the walk once. The indices every named bucket holds, ascending. One bucket is already ascending; a union of several is sorted so a `limit` takes the same neurons a full scan would have taken.

argtypedescription
buckets{ [number]: { number } }
keys{ [number]: boolean }

selectionKey(sel: Selection) → string

argtypedescription
selSelection

remember(self: ?, key: string, answer: { number }) → void

argtypedescription
self?
keystring
answer{ number }

select(sel: Selection) →

The neurons a selection names, as an array of indices (from 0). A selection combines any of: `types` (exact type names), `typePrefix`, `pattern` (a Lua pattern over the type name), `classes`, `superclasses`, `sides`, `excitatory`, `indices`; every given key must hold. `limit` caps the count. The array is the network's own, memoized on the selection, so read it rather than writing into it.

argtypedescription
selSelectionThe selection.

examples

local mn9 = brain:select({ types = { "MN9" } })

consider(axis: string, keys: { [number]: boolean }?) → void

argtypedescription
axisstring
keys{ [number]: boolean }?

test(i: number) → boolean

argtypedescription
inumber

resolveSelection(self: ?, sel: any) → void

argtypedescription
self?
selany

effectiveDrive(self: ?, i: number) → number

argtypedescription
self?
inumber

stimulate(sel: any, rateHz: number, source: string?) → number

Drive a set of neurons with external spikes at a Poisson rate. A rate of 0 stops this source driving them. The rate a neuron actually sees is the largest any source asked for, so the fly's own senses and the bench's experiments can drive the same neurons without taking each other's drive away. Stimulation persists across `reset`. passes `"fly"`, the bench `"bench"`, a protocol `"protocol"`; a call that names none is recorded as `"code"`.

argtypedescription
selanyA selection, or an array of indices.
rateHznumberSpikes per second per neuron.
sourcestring?Who is driving, for `drives` and `clearStimulation`. The fly

examples

brain:stimulate({ types = { "claw_tpGRN" } }, 100, "bench")

clearStimulation(source: string?) → number

Stop one source's external drive, or every source's.

argtypedescription
sourcestring?The source to clear. Omitted, every drive goes.

examples

brain:clearStimulation("bench")

drives( ) →

Who is driving the network right now, one row per source. neurons that source drives and `hz` the highest rate it asked for.

examples

for _, d in ipairs(brain:drives()) do print(d.source, d.count, d.hz) end

silence(sel: any, silenced: boolean) → number

Silence a set of neurons (an ablation: they never spike) or restore them.

argtypedescription
selanyA selection, or an array of indices.
silencedbooleanTrue to silence, false to restore.

examples

brain:silence({ types = { "DNp01" } }, true)

slotOf(w: number, s: number) → number

argtypedescription
wnumber
snumber

withSlot(w: number, s: number, id: number) → number

argtypedescription
wnumber
snumber
idnumber

clearGroupIndices(self: ?, id: number, indices: { number }) → void

Take a group off the neurons it was placed on. The group's own index list is the record of where that is, so a re-watch costs the size of the group rather than the size of the network.

argtypedescription
self?
idnumber
indices{ number }

watch(name: string, sel: any) → number

Read a set of neurons out under a name: from then on `rates()` reports their mean firing rate. A neuron reads out under at most three groups at once, and a watch that would need a fourth slot on any neuron is refused, naming the neuron and the groups it already carries, so a new readout can never take one something else depends on. Watching a name again with the same selection is a no-op; with a different one it replaces the selection. Up to 255 groups.

argtypedescription
namestringThe group's name.
selanyA selection, or an array of indices.

examples

brain:watch("MN9", { types = { "MN9" } })

unwatch(name: string) → boolean

Stop reading a group out. Its name, its id and the readout slots it held on every neuron are released.

argtypedescription
namestringThe group's name.

examples

brain:unwatch("MN9")

rates( ) →

The mean firing rate of every watched group, in spikes per second per neuron, over the steps between the last two counter readbacks.

examples

for name, hz in pairs(brain:rates()) do print(name, hz) end

activity( ) →

The mean firing rate over the whole network, Hz per neuron, and the spikes the list could not hold (which lose their propagation).

examples

print(brain:activity().hz)

group(name: string) →

The indices a watched group holds.

argtypedescription
namestringThe group's name.

examples

brain:group("MN9")

classRates(limit: number?) →

The cell classes with the most activity right now, by the mean of the 60 ms spike trace over every neuron of the class. The trace is set to 1 at a spike and decays, so this is activity, not a rate in Hz, and a class firing faster than the trace decays reads above 1. Asking for it arms the per-neuron readback that answers it, so the first call after a quiet period returns the previous sweep and the next one is current.

argtypedescription
limitnumber?How many classes to return, most active first. Default 10.

examples

for _, c in ipairs(brain:classRates(5)) do print(c.class, c.activity) end

groupActivity(name: string) →

The activity of each neuron of a watched group, in the order `group(name)` lists them, from the same 60 ms trace `classRates` reads. A group of more than 32 neurons answers nil: this is what a raster draws a row from, and a raster of more rows than that is a bar.

argtypedescription
namestringThe group's name.

examples

local rows = brain:groupActivity("MN9")

readActivity( ) →

Start an asynchronous read of every neuron's activity lane: the trace, the normalised membrane and the spike flag. Poll the handle's `:state()`; `:result()` is 16 floats per neuron, the first three being those values.

examples

local rb = brain:readActivity()

sliceOf(src: buffer, byteOffset: number, byteCount: number) → buffer

One instanced draw of every neuron that has a soma. The population is built in two halves. `buildCloud` fills the transform and colour buffers, a slice of neurons per frame so no frame carries the whole pass, and `setCloudDrawn` registers or drops the draw without touching those buffers. That split is what lets the component put the registration down while nothing is looking at the brain: a registration costs its whole transform run on the CPU every frame whether or not the cull draws any of it, and 164,587 of those is most of the frame.

argtypedescription
srcbuffer
byteOffsetnumber
byteCountnumber

writeSlot(xf: buffer, slot: number, x: number, y: number, z: number, r: number) → void

Write the transform of one drawn slot. The dataset's y grows ventrally (image rows), the world's y grows up.

argtypedescription
xfbuffer
slotnumber
xnumber
ynumber
znumber
rnumber

scanCloud(self: ?, c: ?) → void

argtypedescription
self?
c?

uploadCloud(self: ?, c: ?) → void

argtypedescription
self?
c?

buildCloud(opts: { [string]: any }?, onReady: ((any) →

Build the neuron cloud's buffers: one instance per neuron that has a soma, placed by the connectome's own coordinates. `origin` places the brain's centre in the world, `scale` is world units per micrometre, `radius` the octahedron's radius in world units. The fill is spread over frames from a task, so no frame carries the whole pass; `built` on the returned record says when it is done. Nothing is drawn until `setCloudDrawn(true)`.

argtypedescription
opts{ [string]: any }?`{ origin?, scale?, radius?, material? }`.
onReady((anyCalled with the cloud record once the buffers are filled.

examples

brain:buildCloud({ origin = { 0, 5.5, -9 }, scale = 0.01, radius = 0.012 })

setCloudDrawn(on: boolean) → boolean

Put the cloud's draw up or take it down, keeping every buffer. This is the call that costs or saves the frame: a registered population has its whole transform run recomposed on the CPU every frame, whether or not the cull draws any of it, so a cloud nothing is looking at is worth dropping and putting straight back.

argtypedescription
onbooleanRegister the draw, or drop it.

examples

brain:setCloudDrawn(false)

cloudDrawn( ) → boolean

Whether the cloud's draw is registered right now.

examples

print(brain:cloudDrawn())

cloudBounds( ) →

The cloud's world-space bounding sphere, which is what a visibility test needs.

examples

local x, y, z, r = brain:cloudBounds()

showCloud(opts: { [string]: any }?) →

Build the cloud and draw it. The buffers fill over the next frames, and the draw goes up when they are ready.

argtypedescription
opts{ [string]: any }?`{ origin?, scale?, radius?, material? }`.

examples

brain:showCloud({ origin = { 0, 5.5, -9 }, scale = 0.01, radius = 0.012 })

setCloudOrigin(origin: { number }) →

Move the cloud to a new origin without rebuilding it: each slot's transform is rewritten from the neuron record it already draws, a slice a frame, and pushed to the buffer the draw is already reading. Every slice writes the position the CURRENT origin puts that neuron at, so a move that arrives while another is still running replaces it and the cloud still lands whole at the last origin asked for.

argtypedescription
origin{ number }`{ x, y, z }` in world units.

examples

brain:setCloudOrigin({ 0, 7.2, 9 })

worldPosition(i: number) →

Where a neuron sits in the world while a cloud exists, whether or not its draw is registered.

argtypedescription
inumberThe neuron index.

examples

local x, y, z = brain:worldPosition(i)

neuronAt(screenX: number, screenY: number, radiusPx: number?) → number

The drawn neuron nearest a point on screen, for a click in the cloud. Every drawn slot is projected with the active camera's own view-projection and the nearest one inside `radiusPx` wins, the nearer of two overlapping neurons taking it.

argtypedescription
screenXnumberPixels from the left of the viewport.
screenYnumberPixels from the top.
radiusPxnumber?How far from the point to look. Default 12.

examples

local i = brain:neuronAt(405, 540)

hideCloud( ) →

Take the neuron cloud down and release everything it holds.

examples

brain:hideCloud()

destroy( ) →

Release every GPU buffer the network holds. The handle is dead after this.

examples

brain:destroy()

describe( ) →

A one-table summary for logs and inspectors.

examples

print(brain:describe().hz)
⌬ Types
Selection = {Params = {
⌬ Metadata
descriptionRuns any connectome asset as a leaky integrate-and-fire spiking network on the GPU: step, stimulate by source, silence, read out by group, select by cell type, and draw every soma as a point lit by its own activity.

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❒
package · born here
❒asset
# fruitFly A whole fruit fly nervous system running as a spiking network on the GPU, a fly body it drives, and a bench for experiments on it. Install this package and a world holds the complete adult male *Drosophila* central nervous system (MaleCNS v1.0: 164,587 neurons, 25.6 million connections, CC-BY 4.0) as a leaky integrate-and-fire network you can stimulate, silence, read out and watch, plus a fly whose taste, looming, walking, turning, feeding, flight and escape run through that wiring. ## Contents The network: - `maleCNS.connectome/` is MaleCNS v1.0 packed for the GPU (109 MB, the edge table in two parts). It is an instance of the `connectome` asset type, which lives at the world root (`/zero/source/connectome.assetType/`) and travels with the package as a dependency: any nervous system's wiring as one asset (`manifest.json`, `neurons.bin`, `offsets.bin`, `edges.bin` or its parts). `guides { path = "types/connectome" }` is the reference. - `lif_integrate`, `lif_propagate`, `lif_clear`, `lif_reset` (`.computeShader`) are the four kernels of the network: membrane step, event-driven spike propagation over the CSR edge table, step close, reset. - `brain.module/` is `Brain.load(connectomeRef, params)`, which binds a connectome to the kernels and returns the network: `step`, `update`, `select`, `stimulate`, `silence`, `watch`, `rates`, `activity`, `classRates`, `groupActivity`, `drives` and the cloud. - `FruitFlyBrain.component/` puts a network on an entity: it loads the connectome the `connectome` field names, steps it every frame, draws the cloud, and exposes `stimulate` / `silence` / `watch` / `rates` / `reset` (the first three are synced, so every peer's copy receives the same inputs). - `neuron.shader/`, `neuron.material/` and `cloud_gather.computeShader/` are the instanced neuron cloud, each neuron lit by its own activity. - `crackle.soundClip/` is the network's own sound: a sparse crackle that is silent when the network is silent and a hiss when it runs away. The fly: - `flyBody.module/` is the fly's body as an entity tree with a tripod gait, wings, proboscis and a hop. - `FruitFly.component/` is the embodied fly: it reads the world into the brain's sensory neurons and reads motor commands back out of named cell types. - `FoodPatch.component/` is a disc of food on the ground the fly can taste. - `wing.material/`, `eye.material/` and the `wingbeat`, `feed` and `jump` sound clips are what the fly looks and sounds like. The instrument: - `FruitFlyLab.component/` is the bench window: network state and knobs, live readouts with traces and rasters, hot classes, live drives, a neuron panel, a legend, and a selection line to stimulate, silence, restore, count or watch any set of neurons. - `selection.module/` is the selection grammar the bench and everything else parse with. - `protocol.module/` is the guide's experiments as records anything can run, and the verdict a run computes from its own numbers. - `FruitFlyExperiments.component/` is the experiments panel: those protocols with one press each, a run list, a compare overlay and a verdict line. - `FirstRun.component/` is the four-step card that walks a newcomer from a reset network to a proboscis coming out. - `lab.inputMap/` and `experiments.inputMap/` are the bench's and the panel's controls, each binding keyboard, gamepad and touch. - `experiments.guide/` is the bench manual and the five experiments. The lab around it: - `labFloor.material/` and `FruitFlyLook.component/` are the floor, the fog, the vignette and the lighting intent, held as data rather than as code. - `arenaRing.mesh/` is the ring on the floor the fly stays inside. ## Usage ```luau -- The brain: one entity, one network. The default connectome is maleCNS. local brainEnt = entity.spawn("Brain") brainEnt.position = { 0, 6, -8 } brainEnt.component.add("FruitFlyBrain", { gain = 0.6, timeScale = 1 }) -- An embodied fly driven by it, and something for it to taste. local fly = entity.spawn("Fly") fly.component.add("FruitFly", { brain = brainEnt, bodyLength = 0.6 }) local food = entity.spawn("Food") food.position = { 3, 0, 0 } food.component.add("FoodPatch", { radius = 0.6, sugar = 1 }) -- The bench, the experiments panel and the card. entity.spawn("Lab").component.add("FruitFlyLab", { brain = brainEnt, fly = fly }) entity.spawn("Experiments").component.add("FruitFlyExperiments", { brain = brainEnt, fly = fly }) entity.spawn("FirstRun").component.add("FirstRun", { brain = brainEnt, fly = fly }) -- Or from code: local comp = brainEnt.component.get("FruitFlyBrain") comp:watch("MN9", { types = { "MN9" } }) -- proboscis motor neurons comp:stimulate({ types = { "claw_tpGRN" } }, 100) -- tarsal taste pegs at 100 Hz print(comp:rates().MN9) -- Hz per neuron, updated every frame ``` A selection names neurons by the dataset's own vocabulary: `types` (exact cell-type names), `typePrefix`, `pattern` (a Lua pattern over the type name), `classes`, `superclasses`, `sides` (`L`/`R`/`M`), `excitatory`, `indices`, `limit`. `brain:info(i)` answers what any neuron is. ## The model Every neuron is a leaky integrate-and-fire unit with the constants Shiu et al. 2024 (Nature) fitted to the FlyWire brain: rest and reset at -52 mV, threshold -45 mV, membrane time constant 20 ms, synaptic time constant 5 ms, refractory period 2.2 ms, transmission delay 1.8 ms, 0.275 mV per synapse. A presynaptic neuron whose consensus transmitter is GABA, glutamate or histamine inhibits; every other transmitter excites. A connection carries its synapse count; connections under `minSynapses` (default 5) carry nothing. `gain` scales every synapse. MaleCNS traces about 2.5 times the synapses per connection FlyWire does, so at gain 1 the network runs away under any drive; at 0.6 (the default) driving the 50 tarsal taste-peg neurons at 100 Hz holds the proboscis motor neurons MN9 at about 115 Hz while the Kenyon cells stay under 0.1 Hz, and driving the 595 Johnston's organ neurons instead leaves MN9 at zero. At 0.5 the taste drive reaches nothing. The bench's gain slider is the experiment, and the experiments panel's "Gain recovery" runs all three in one press. Everything runs on the GPU: the state, the input ring, the spike list and the edge table. The CPU sees the per-group spike counters each frame and, on request, the per-neuron activity lane. Integer atomics make a step order-independent, so two peers stepping the same inputs read the same network. ## The fly `FruitFly` reads named cell types out of the brain and writes the world into others; every name is in `FruitFly.component/init.luau`: | command | cell types | |---|---| | walk | the leg motor neurons (`vnc_motor` types ending in ` MN`), per side | | turn | `DNa01`, `DNa02` left minus right | | proboscis | `MN9` | | flight | the wing power-muscle motor neurons (`DLMn`, `DVMn`) | | jump | a `DNp01` (giant fibre) burst | | sense | cell types | driven by | |---|---|---| | tarsal taste | `claw_tpGRN`, `dorsal_tpGRN`, per side | that side's front foot on a `FoodPatch` | | labellar taste | `LB*` labellar bristle GRNs | the extended proboscis on a `FoodPatch` | | looming, LPLC2 path | `LPLC2` | a player's avatar growing fast in front of the fly | | looming, LC4 path | `LC4` | the same, driven as a separate path so one can be silenced | The two looming paths are driven separately and weighted by how head-on the approach is, so an avatar walking up behind the fly does not loom and silencing one detector class is an experiment with an answer. The body moves kinematically at `walkSpeed` body lengths per second; the fly faces its entity's -Z. On a shared world the entity's owner writes the senses into the brain (a synced call) and every peer poses its own copy from its own network. ## Controls | Action | Keyboard | Gamepad | Touch | |---|---|---|---| | Bench: show or hide | L | Start | The "Lab" button | | Bench: move focus | Down and Up, Tab | D-pad down and up | Tap the control | | Bench: activate the focused control | Enter | North (Y) | Tap | | Bench: nudge the focused slider | Left and Right | D-pad left and right | Drag it | | Bench: identify a neuron | Click it in the cloud | West (X) | Tap it | | Experiments: show or hide | P | Select | The "Experiments" button | | Experiments: next protocol | N | Right stick press | Tap the protocol | | Experiments: previous protocol | B | None: the list wraps | Tap the protocol | | Experiments: run | R | Right trigger | RUN | | Experiments: compare | C | Left trigger | COMPARE | Both maps name their controls apart (`lab*` and `exp*`) and take disjoint keys and buttons, so the bench and the panel can be open together and neither answers for the other. ## Data and license MaleCNS v1.0: HHMI Janelia FlyEM, Google Research and the Cambridge connectomics group, released 8 June 2026 (Berg et al. 2026, Cell, doi:10.1016/j.cell.2026.08.015), CC-BY 4.0. The pack was written by a script that reads the public flat-connectome export (`connectome-weights ... traced-only`, body annotations, consensus neurotransmitters), assigns dense indices, sorts edges by presynaptic neuron and writes the four files `types/connectome` describes; the manifest carries each source file's SHA-256. ## Notes - Loading the network reads the 102 MB edge table into a GPU buffer once per `FruitFlyBrain`; the VFS copy is released afterwards. - The neuron cloud is one instanced draw of every neuron with a soma (139,741). Its transforms are static; the activity lanes are written by the integrate kernel. - `maxStepsPerFrame` bounds GPU time per frame; at 32 steps of 1 ms a 60 fps engine keeps up with real time. - A neuron reads out under at most three groups at once. The fly holds seven of its own and the protocols watch five more under the guide's names, so a bench watch of the same cell types under the same name shares the group rather than spending another slot.
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# lif_propagate The synaptic step of the `brain` module's network. Each workgroup takes one spike from this step's list, and its 64 threads stride that neuron's outgoing edge row, adding every connection's synapse count times `unitsPerSynapse` (signed by the presynaptic neuron's transmitter) into the fixed-point input ring at the slot `delaySteps` after the current step. A connection carrying fewer than `minSynapses` synapses is skipped, which is how the module applies the connection threshold whole-brain models are fitted with (five, in Shiu et al. 2024) without repacking the table. The module dispatches it with `maxSpikes` workgroups; a workgroup past this step's spike count returns at once. The sum is integer atomics, so the result is the same whatever order the threads land in.
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# lif_reset Puts the `brain` module's network at rest in one dispatch: every membrane at `vRest` with no synaptic conductance, refractory time or activity trace, every slot of the input ring empty, the visualisation lane dark, the spike list empty, every spike counter zero and the step clock at zero. The module runs it once after allocating a network and again on `brain:reset()`.
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# cloud_gather Copies each drawn cloud slot's activity out of the neuron that slot draws. The `brain` module registers one instance per neuron that has a soma, which is 139,741 of the male CNS's 164,587, so the slots are packed and slot `s` is not neuron `s`. The integrate kernel writes its activity lane at each neuron's own index, so without this pass every slot would be lit by the wrong neuron. It reads `slotmap[s]`, the neuron index the module recorded for that slot when it built the cloud, and copies the three values of that neuron's lane 0 into `cloudviz[s]`, which is the buffer the instanced draw hands the neuron material as `input.shader_data[0]`. Lane 1 of `cloudviz` is the slot's resting colour, written once from the CPU at build, and this kernel leaves it alone. `Brain:step` dispatches it once after the frame's last simulation step, and only while the cloud's draw is registered. Bindings: `viz` (read), `slotmap` (read), `cloudviz` (read_write). Param: `drawn`, the registered instance count. One thread per slot at a workgroup size of 64.
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# lif_integrate The membrane step of the `brain` module's leaky integrate-and-fire network, one thread per neuron. It drains this step's slot of the fixed-point input ring into the neuron's synaptic conductance, advances the membrane by exponential Euler on `dv/dt = (vRest - v + g) / tauM` and `dg/dt = -g / tauSyn`, holds a refractory neuron at reset, draws the neuron's external Poisson event from its `stim` rate, and on a spike resets it, appends its index to this step's spike list, and bumps the total and its readout group's counter. Every neuron writes its activity trace, normalised membrane and spike flag into lane 0 of the visualisation buffer the neuron cloud draws from. `decayMem` and `decaySyn` are `exp(-dt / tau)` computed once by the module; the step index comes from the GPU clock so several steps can be queued in one frame with no CPU write between them.
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# lif_clear Closes one step of the `brain` module's network: empties the spike list the integrate kernel filled and the propagate kernel consumed, and advances the GPU step clock by one. The clock living on the GPU is what lets the module queue several steps in one frame, each reading its own ring slot, with no CPU write between dispatches.
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backing path · fruitFly.package/brain.module

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