Multiplicative modulations enhance diversity of hue-selective cells

Paria Mehrani,Andrei Mouraviev,John K Tsotsos

doi:10.1038/s41598-020-64969-3

Abstract

There is still much to understand about the brain’s colour processing mechanisms and the transformation from cone-opponent representations to perceptual hues. Moreover, it is unclear which area(s) in the brain represent unique hues. We propose a hierarchical model inspired by the neuronal mechanisms in the brain for local hue representation, which reveals the contributions of each visual cortical area in hue representation. Hue encoding is achieved through incrementally increasing processing nonlinearities beginning with cone input. Besides employing nonlinear rectifications, we propose multiplicative modulations as a form of nonlinearity. Our simulation results indicate that multiplicative modulations have significant contributions in encoding of hues along intermediate directions in the MacLeod-Boynton diagram and that our model V2 neurons have the capacity to encode unique hues. Additionally, responses of our model neurons resemble those of biological colour cells, suggesting that our model provides a novel formulation of the brain’s colour processing pathway.

Highlights

There is still much to understand about the brain’s colour processing mechanisms and the transformation from cone-opponent representations to perceptual hues
Perhaps clustering of the majority of unique hues along intermediate directions could describe the suggestion by Wuerger et al.[26] who proposed that the encoding of unique hues, unlike the tuning of LGN neurons, needs higher order mechanisms such as a piecewise linear model in terms of cone inputs
Our goal was to further understanding of the colour processing mechanisms in the brain and to begin to assign colour representational roles to specific brain areas

Summary

Introduction

There is still much to understand about the brain’s colour processing mechanisms and the transformation from cone-opponent representations to perceptual hues It is unclear which area(s) in the brain represent unique hues. Later studies[5,6,7], confirmed that the cone-opponent mechanisms of earlier processing stages do not correspond to Hering’s red vs green and yellow vs blue opponent processes They observed that the colour coding in early stages is organized along the two dimensions of the MacLeod and Boynton (MB)[8] diagram, where abscissa and ordinate represent L vs M and S vs LM activations respectively. Perhaps clustering of the majority of unique hues along intermediate directions could describe the suggestion by Wuerger et al.[26] who proposed that the encoding of unique hues, unlike the tuning of LGN neurons, needs higher order mechanisms such as a piecewise linear model in terms of cone inputs. Zaidi et al.[30] observed no significance of unique hues in human subjects and responses of IT neurons, confirmed in more recent studies[31,32]

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