Finding independent components using spikes: A natural result of hebbian learning in a sparse spike coding scheme

摘要

As an alternative to classical representations in machine learning algorithms, we explore coding strategies using events as is observed for spiking neurons in the central nervous system. Focusing on visual processing, we have previously shown that we can define with an over-complete dictionary a sparse spike coding scheme by implementing lateral interactions that account for redundant information. Since this class of algorithms is both compatible with biological constraints and with neuro-physiological observations, it can provide a possible algorithm to explain the speed of visual processing despite the relatively slow time of response of single neurons. Here, I explore learning mechanisms to derive in an unsupervised manner an over-complete set of filters which provides a progressively sparser representation of the input. This work is based on a previous model of sparse coding from Olshausen et al. (1998) and the results leads to similar results, suggesting that this strategy provides a simple neural implementation of this algorithm and thus of Blind Source Separation. Moreover, this neuro-mimetic algorithm may be easily extended to realistic architectures of cortical columns in the primary visual cortex and we show results for different strategies of representation, leading to neuro-mimetic adaptive sparse spike coding schemes.