Neuron Chain

one signal at the front, and a cascade — or a message that goes nowhere

three.js · webgl

Start here

A neuron has a bushy crown of dendrites around its cell body, the soma, and axons running to other cells. The bush listens. The fibres carry.

Each cell sits at about −70 mV. Every incoming spike nudges that voltage, and the membrane leaks back down in between. Only if the voltage climbs to −55 mV does the cell fire.

This is the important part: one input is usually not enough. Several have to arrive close enough together to add up before the leak drains them — and about one in five synapses is inhibitory and pushes the voltage the wrong way.

Watch for the amber cells. Those are charged but not yet fired — caught mid-decision. Bright tips mark terminals a spike reached.

This run

Which thought?

What happened

Nothing yet — trigger the input.

Fire it

Or click anywhere in the scene · drag to orbit · scroll to zoom · Space fires, R resets.

The membrane

Every cell rests at −70 mV and fires when it reaches −55 mV.

Synapse strength 9.0 mV

How far one excitatory input pushes the target. Below 15 mV a single input cannot reach threshold on its own, so the cell has to sum several — which is how a real neuron works.

Summation window 45 ms

The membrane leaks back toward rest between inputs. A long window lets inputs arriving at different times still add up; a short one means they must land almost together.

Synaptic weight spread 0.55

How much synapses differ in strength. At 0 they are identical; turn it up and the network gets patchy, like a real one.

The network

Inhibitory synapses 20%

Roughly one in five cortical neurons is inhibitory — it pushes the target away from threshold instead of toward it. Violet axons. Without them a network like this runs away with itself.

Layers 3 Cells per layer 7

Playback speed 0.35×

A real cascade like this is over in under a tenth of a second. Everything here is slowed about a hundredfold so it can be watched at all; this is the playback rate on top of that.

Myelination 1.00×

Real axons are wrapped in a myelin sheath and the spike jumps between gaps in it, travelling far faster than on a bare fibre.

Every term on this page

the simulation

At rest

building the network…

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