Visual Information flow in Wilson-Cowan networks

Abstract

In this work we study the communication efficiency of a psychophysically-tuned cascade of Wilson-Cowan and Divisive Normalization layers that simulate the retina-V1 pathway. This is the first analysis of Wilson-Cowan networks in terms of multivariate total correlation. The parameters of the cortical model have been derived through the relation between the steady state of the Wilson-Cowan model and the Divisive Normalization model.Efficiency has been analyzed in two ways: First, we provide an analytical expression for the reduction of the total correlation among the responses of a V1-like population after the Wilson-Cowan interaction. Second, we empirically study the efficiency with visual stimuli and statistical tools that were not available before: (1) a recent, radiometrically calibrated, set of natural scenes, and (2) a recent technique to estimate the multivariate total correlation in bits from sets of visual responses which only involves univariate operations, thus giving better redundancy estimates.The theoretical and the empirical results show that although this cascade of layers was not optimized for statistical independence in any way, the redundancy between the responses gets substantially reduced along the pathway. Specifically, we show that (1) the efficiency of a Wilson-Cowan network is similar to its equivalent Divisive Normalization, (2) while initial layers (Von-Kries adaptation and Weber-like brightness) contribute to univariate equalization, the bigger contributions to the reduction in total correlation come from the nonlinear local contrast and the local oriented filters, and (3) psychophysically-tuned models are more efficient in the more populated regions of the luminance-contrast plane. These results are an alternative confirmation of the Efficient Coding Hypothesis for the Wilson-Cowan systems. And from an applied perspective, they suggest that neural field models could be an option in image coding to perform image compression.