The tree-receptor theory of human color vision accounts for color matching. A bottom-up, non-linear model combining cone signals in six types of cone-opponent cells in the lateral geniculate nucleus (LGN) of primates describes the phenomenological dimensions hue, color strength, and lightness/brightness. Hue shifts with light intensity (the Bezold-Brücke phenomenon), and saturation (the Abney effect) are also accounted for by the opponent model. At the threshold level, sensitivities of the more sensitive primate cells correspond well with human psychophysical thresholds. Conventional Fourier analysis serves well in dealing with the discrimination data, but here we want to take a look at non-linearity, i.e., the neural correlates to perception of color phenomena for small and large fields that span several decades of relative light intensity. We are particularly interested in the mathematical description of spectral opponency, receptive fields, the balance of excitation and inhibition when stimulus size changes, and retina-to-LGN thresholds.
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