Live demo

A renewal-process spike generator that runs in your browser. Set a rate, a regularity and a refractory period, and it draws the raster and the interspike-interval histogram — the same two plots axonforge report produces from real data. It is synthetic ground truth, which is exactly what the validation page tests against.

Intervals are drawn from a gamma renewal process: the shape parameter is 1/CV², so regularity below 1 makes a pacemaker-like train and above 1 makes a bursty one, and every interval is clamped to at least the refractory period. The sequence is deterministic from the seed, so the same settings always give the same picture.

Raster: one row per trial, one tick per spike. Time runs left to right.

Interspike-interval histogram over all trials, in milliseconds. The gap at the left is the refractory period; nothing shorter is generated.

Scripts are off, so the controls do nothing. The example below is a static render at rate 20 Hz, CV 0.8, 2 ms refractory — turn scripts on to change it.

Reading the two plots#

A low CV packs the ticks into near-even columns and gives a sharp, narrow ISI histogram; a CV above 1 clumps them and gives a long tail.
The refractory period is visible as the empty bin on the left of the histogram. It is what quality.isi_violations counts crossings of on real data.
The measured rate printed above the raster is spikes divided by the total recording time; it drifts slightly from the set rate because the refractory clamp removes the shortest intervals, which raises the mean interval and lowers the rate.

What this is not

This is a single-unit generator for intuition, not a recording simulator: there is no noise, no waveform, no overlap between units and no drift. The synthetic benchmark on the validation page adds all of those, which is why its recall is below one even at high signal-to-noise.