---
tags:
- spiking-neural-network
- snn
- sparse
- brain-inspired
- connectome
- drosophila
- mnist
- fashion-mnist
- image-classification
- awareliquid
pipeline_tag: image-classification
---

# Sparse-SNN — connectome-inspired sparse spiking networks

**Sparse spiking neural networks whose structural masks are derived from the
statistical laws of the real *Drosophila* connectome** — matching dense MLP
accuracy at ~2 orders of magnitude lower energy.

Two trained classifiers: MNIST and Fashion-MNIST. Architecture: `784 → 800 → 10`
with 5% connection density, LIF neurons and surrogate-gradient training
(straight-through estimator with sigmoid gradient).

## Files

| File | Description |
|---|---|
| `sparse_snn_mnist.pt` | MNIST checkpoint — **96.83%** test accuracy (firing rate 7.9%) |
| `sparse_snn_fashion.pt` | Fashion-MNIST checkpoint — **87.07%** test accuracy (firing rate 8.2%) |
| `train_results.json` | Raw metrics from the training runs |

Each checkpoint contains the `state_dict` (weights + mask buffer), the E/I sign
matrix, the full config, and metrics.

## ResNet SNN — CIFAR-10 (2026-09, human-brain-simulation repo)

ResNet-style spiking network (LIF + firing-rate residuals) trained directly on
CIFAR-10, six-experiment series, all recorded:

| Experiment | CIFAR-10 |
|---|---|
| **ResNet SNN v1 (3 residual blocks, 60 ep)** | **84.76%** |
| v1 + 200 ep + Cutout (long training) | **84.89%** |
| Full-depth ResNet-18 (9 LIF layers) | 67.93% (spike death) |
| Wide channels 96/192/384 | 66.96–75.50% (fixed-threshold saturation) |
| PLIF learnable threshold + Cutout | 83.43% |

Honest ceiling: **~85%** for this direct-training recipe family on CIFAR-10
(dense CNN baseline 75.00%; VGG-SNN variant 86.22% in the same repo). 90%+
needs a different route (T≥10 + threshold balancing, or ANN→SNN conversion
calibration). Details: github.com/AwareLiquid/human-brain-simulation.

## Measured results (these checkpoints)

| Task | Dense MLP (documented) | Sparse SNN (this checkpoint) | Gap | Energy saving* |
|---|---|---|---|---|
| MNIST | 98.32% | **96.83%** | 1.5 pts | **~112×** |
| Fashion-MNIST | 87.56% | **87.07%** | 0.5 pts | **~107×** |

\* Energy estimate using the repository's 45nm CMOS model (Horowitz 2014:
MAC = 3.7 pJ, addition = 0.9 pJ) with this checkpoint's measured firing rate —
event-driven spike ops are additions only. This is a **model-based estimate,
not measured on hardware**. The project's documented headline range across runs
is 105–106×.

## What the research found (and disproved)

1. **Disproved**: the MaleCNS connectome topology as a *static* structure
   carries **no measurable advantage** over random / structured-sparse graphs
   (5 experiments: classification, temporal, robustness, sample-efficiency,
   plasticity — all indistinguishable).
2. **Extracted** — the topology's *statistical laws* that DO matter:
   sparsity **0.09%**, long-tail degree distribution (scale-free, max/mean ≈ 75),
   strong small-worldness (clustering 6.65× random, path length 2.39),
   **E/I ratio 60/40**.
3. **Built**: a trainable sparse SNN from these laws → near-lossless accuracy
   at ~105–112× energy savings.

## Usage

Requires the model code from the repository (the class is small and
self-contained):

```python
import torch
from sparse_snn import SparseSNN   # github.com/AwareLiquid/human-brain-simulation

ckpt = torch.load("sparse_snn_mnist.pt", map_location="cpu", weights_only=False)
cfg = ckpt["config"]
model = SparseSNN(cfg["in_dim"], cfg["hid_dim"], cfg["out_dim"],
                  ckpt["state_dict"]["mask"], ckpt["sign"],
                  T=cfg["T"], decay=cfg["decay"], threshold=cfg["threshold"])
model.load_state_dict(ckpt["state_dict"])
model.eval()
# inputs: flattened 28x28 grayscale in [0, 1]
```

Loading was verified to reproduce the saved accuracy bit-exactly
(`acc=0.9683` MNIST / `acc=0.8707` Fashion on reload).

## Honest boundaries

- The accuracy gap vs a dense MLP is small but real (1.5 pts MNIST, 0.5 pts
  Fashion) — "near-lossless", not lossless.
- The connectome's *static topology* gave no advantage; only its statistical
  laws transferred. Do not attribute the result to "copying the fly brain".
- Energy figures are analytic (45nm CMOS), not measured on neuromorphic
  hardware.
- Recurrent spiking training remains an open problem in this line (sMNIST from
  scratch reaches only ~70%; conversion methods do better but lose efficiency).
- Masks are generated with a fixed seed (`mask_seed=0`) — rerun the code in the
  repository to regenerate the exact structure.

## Related

- Code & full experiment report: [AwareLiquid/human-brain-simulation](https://github.com/AwareLiquid/human-brain-simulation)
- [AwareLiquid/M1](https://github.com/AwareLiquid/M1) — MT-LNN liquid architecture
- [awareliquid.ai](https://awareliquid.ai) — benchmarks and retractions


## Try it

- 🎮 Interactive demo (runs in your browser, ONNX Runtime Web): https://huggingface.co/spaces/AwareLiquid/Sparse-SNN-demo

## License

MIT. MaleCNS connectome data is CC-BY 4.0 (HHMI Janelia / Cambridge / Google
Research, male-cns.janelia.org) — not redistributed here.