005 — PING Integration Step Video
Abstract
Gamma has a period of 15–30 ms, so a coarse integration step dt can’t resolve the E→I→E round-trip. With the Poisson input overdrive pinned well past the PING threshold from nb003 (so the rhythm would be robust at fine dt), this notebook sweeps dt — isolating the timestep as the only knob that can break the oscillation. Companion sweeps: nb003 (drive) and nb006 (E→I coupling); companion dt-stability training experiment is nb013. See The Notebooks for how this entry’s runner/artifact/figure triple is wired up.
Methods
A scan over the oscilloscope video subcommand with stim-overdrive held at 10× (firmly inside the stable-PING regime mapped by nb003) while dt sweeps 0.05 → 2 ms over 300 frames. All knobs are hardcoded literals in src/pinglab/notebooks/nb005.py per the runner contract.
| Parameter | Value |
|---|---|
| Setup | |
| Model | ping |
| Input | mnist d0 s0 |
| Seed | 42 |
| Architecture | |
| N_E / N_I | 512 / 128 |
| T | 600 ms |
| Stimulus & scan | |
| Stim window | 200–300 ms |
| Fixed overdrive | 10× |
| dt scan | 0.05–2 ms |
| Frames / FPS | 300 / 30 |
| Provenance | |
| Tier | large |
| Elapsed | 24m 39s |
| Run ID | r002 |
| Git SHA | ? |
Results
Each frame is a fresh 600 ms sim on MNIST digit 0, sample 0 with stim-overdrive held at 10×. dt sweeps 0.05 → 2 ms over 300 frames.
Stable until about dt = 1.65 ms; beyond that the whole population saturates after PING onset.
Population rates
| Window | E (Hz) | I (Hz) |
|---|---|---|
| Pre-stim | 6.8 | 0.0 |
| In-stim | 20.5 | 54.2 |
| Post-stim | 5.6 | 1.6 |
Discussion
TODO: discussion paragraph — write what the results above mean for the project.
Next steps
The breakdown around dt ≈ 1.65 ms sets a hard ceiling on the timestep any downstream training entry can use without losing the rhythm. nb013 tests whether this same ceiling holds end-to-end through training — i.e. whether a model trained at dt near the limit still produces PING at inference. The breakdown mode here (saturation, not collapse) suggests the failure is integrator instability rather than loss of the rhythm itself; a side-by-side with explicit-Euler vs the current scheme would isolate that.
Appendix
Reproduction
uv run src/pinglab/notebooks/nb005.py