Research map / Architectures and efficiency / Spiking networks
P-SPIKESSM: HARNESSING PROBABILISTIC SPIKING STATE SPACE MODELS FOR LONG-RANGE DEPENDENCY TASKS
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Proposes P-SpikeSSM, a probabilistic spiking state-space model that samples spikes from SSM-derived firing probabilities (SpikeSampler), uses a surrogate gradient, SpikeMixer and ClampFuse layers, and reports SOTA among SNNs on LRA, psMNIST and SC10.
Problem
Scalable spiking neural networks for long-range dependency sequence tasks are limited by scalar LIF membrane state, sequential spike generation with Heaviside functions, and BPTT training costs.
Approach
Replace LIF neurons with an SSM neuron (n-dimensional hidden state, HiPPO-initialized) whose clamped output is used as the Bernoulli spiking probability; spikes are sampled stochastically, the process is computed as a parallel convolution over spikes, and the backward pass uses the expected value E[S_t]=p_s[t] as a surrogate gradient.
Key results
- On psMNIST, P-SpikeSSM reaches 98.4% accuracy, the best among listed SNNs and above the non-spiking Transformer (97.9%) and LSTM (95.1%).
- On LRA, P-SpikeSSM averages higher than other spiking models on Retrieval (88.53), Text (81.20), and Image (82.40), but is below S4 (Original) on ListOps and Pathfinder.
- Energy analysis on ListOps estimates the SNN is 36x more energy efficient than a non-spiking S4 model under the stated ACC/MAC cost assumptions.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use P-SpikeSSM rather than S4 | psMNIST · psMNIST test | accuracy: 98.7 -> 98.4 | Hurt |
| Use P-SpikeSSM rather than S4 (Improved) | LRA ListOps · LRA ListOps test | accuracy: 59.60 -> 58.20 | Hurt |
| Use P-SpikeSSM rather than S4 (Improved) | LRA Text · LRA Text test | accuracy: 86.82 -> 81.20 | Hurt |
| Use P-SpikeSSM rather than S4 (Improved) | LRA Retrieval · LRA Retrieval test | accuracy: 90.90 -> 88.53 | Hurt |
| Use P-SpikeSSM rather than S4 (Improved) | LRA Image · LRA Image test | accuracy: 88.65 -> 82.40 | Hurt |
| Use P-SpikeSSM rather than S4 (Improved) | LRA Pathfinder · LRA Pathfinder test | accuracy: 94.20 -> 84.80 | Hurt |
| Use P-SpikeSSM rather than S4 | SC10 · SC10 test | accuracy: 98.3 -> 95.6 | Hurt |
| Add the surrogate gradient (ablation) | P-SpikeSSM · LRA Text test | accuracy: 70.90 -> 81.20 | Helped |
| Add SpikeMixer (ablation) | P-SpikeSSM · LRA Text test | accuracy: 68.90 -> 81.20 | Helped |
| Add normalization (ablation) | P-SpikeSSM · LRA Text test | accuracy: 77.80 -> 81.20 | Helped |
| Make σ parameters learnable rather than fixed (ablation) | P-SpikeSSM · LRA Text test | accuracy: 80.20 -> 81.20 | Helped |
| Replace GELU with ReLU (ablation) | P-SpikeSSM · LRA Text test | accuracy: 81.20 -> 80.40 | Hurt |
Surprising findings
- Replacing the stochastic SpikeSampler with a deterministic LIF neuron in the same architecture gives lower psMNIST accuracy (97.7% vs 98.4%) and slower training (6.1 vs 1.5 min/epoch).
- Without the surrogate gradient the model fails to exceed random accuracy on ListOps.
Limitations
- Energy analysis covers arithmetic operations only, ignores memory I/O and architectural details, and uses standard convolution instead of FFT.
- Performance on ListOps and Pathfinder trails the original S4 and improved S4 results.
- Some components (gelu in SpikeMixer, normalization in ClampFuse, learnable sigma) involve non-spiking operations that are not fully hardware-friendly.
Experimental setup
Datasets: psMNIST Speech Commands (SC10) Long Range Arena (ListOps, Text, Retrieval, Image, Pathfinder) Speech Commands 35-class
Benchmarks: psMNIST SC10 Long Range Arena Speech Commands 35-class
Metrics: accuracy energy estimate (pJ, ACC vs MAC) training time per epoch active neuron ratio
Baselines: S4 Transformer Linformer Performer Spiking LMUFormer BinaryS4D DSD-SNN HSLMU
Builds on: HiPPO S4 LIF neuron model BinaryS4D Spiking LMUFormer
Closest papers by meaning
- SpikingSSMs: Learning Long Sequences with Sparse and Parallel Spiking State Space Models (AAAI 2025 · similarity 0.92)
- LongSpike: Fractional Order Spiking State Space Models for Efficient Long Sequence Learning (NeurIPS 2026 · similarity 0.90)
- TC-LIF: A Two-Compartment Spiking Neuron Model for Long-Term Sequential Modelling (AAAI 2024 · similarity 0.90)
- The Dormant Spiking Neuron: A State-Driven Mechanism for Efficient Spiking Neural Networks (NeurIPS 2026 · similarity 0.89)
- SpikeLLM: Scaling up Spiking Neural Network to Large Language Models via Saliency-based Spiking (ICLR 2025 · similarity 0.88)
- Learning Delays in Spiking Neural Networks using Dilated Convolutions with Learnable Spacings (ICLR 2024 · similarity 0.88)
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