Event-based circuits for controlling stochastic learning with memristive devices in neuromorphic architectures

Abstract

Memristive devices have emerged as compact nonvolatile memory elements which can be used as synapses in neuromorphic architectures. However, the intrinsic stochasticity in their switching behavior, non-linear characteristics, and variability limit their operation in real systems. In this paper we propose spike-based learning circuits designed to exploit the stochastic properties of memristors. This implements a probabilistic version of a local gradient descent rule, namely the delta rule, for online learning in neuromorphic chips. The circuits proposed translate the delta error to the slope of a ramp voltage which modulates the probability of resistive switching in very low resolution (i.e. binary) memristive devices. We demonstrate the feasibility and computational power of such approach, using a spiking neural network simulator to carry out system level behavioral simulations of the neuromorphic architecture applied to a classification task of digits 0 to 4 in the MNIST data-set.