Lightweight spiking neural network training based on spike timing dependent backpropagation

Abstract

Spiking neural networks are energy efficient and biological interpretability, communicating through sparse, asynchronous spikes, which makes them suitable for neuromorphic hardware. However, due to the nature of binary weights and spike trains in time-coded binarized spiking neural networks, their forward propagation may cause neurons to not fire spikes, and their backward propagation has non-differentiable problems. Moreover, the current use of deep and complex network structures generates a large number of redundant parameters. Therefore, we need effective methods to improve energy efficiency without reducing accuracy. We propose a dynamic threshold model that can reduce the number of dead neurons. We combine the backpropagation algorithm and the spike timing dependent plasticity algorithm to avoid the non-differentiable problem. We propose a neuron pruning strategy based on adaptive firing time threshold. This pruning strategy prunes 267 neurons in a network of 600 neurons, reducing the network size and obtaining a more compact network structure. The energy efficiency is improved by 0.55×, while the classification accuracy is lost by 1.1%.