Color opponency is an efficient representation of spectral properties in natural scenes

Abstract

The human visual system encodes the chromatic signals conveyed by the three types of retinal cone photoreceptors in an opponent fashion. This opponency is thought to reduce redundant information by decorrelating the photoreceptor signals. Correlations in the receptor signals are caused by the substantial overlap of the spectral sensitivities of the receptors, but it is not clear to what extent the properties of natural spectra contribute to the correlations. To investigate the influences of natural spectra and photoreceptor spectral sensitivities, we attempted to find linear codes with minimal redundancy for trichromatic images assuming human cone spectral sensitivities, or hypothetical non-overlapping cone sensitivities, respectively. The resulting properties of basis functions are similar in both cases. They are non-orthogonal, show strong opponency along an achromatic direction (luminance edges) and along chromatic directions, and they achieve a highly efficient encoding of natural chromatic signals. Thus, color opponency arises for the encoding of human cone signals, i.e. with strongly overlapping spectral sensitivities, but also under the assumption of non-overlapping spectral sensitivities. Our results suggest that color opponency may in part be a result of the properties of natural spectra and not solely a consequence of the cone spectral sensitivities.

Spatiotemporal-chromatic structure of natural scenes

“…The latter are, in order, luminance, blue-yellow, and red-green. This result was extended by Wachtler et al [12,13] by replacing PCA with ICA, again for LMS data but now using 7 × 7 patches.…”

The Demands of Geometry on Color Vision

“…Opponency, which has been validated both psychophysically [12] and electrophysiologically [23,24] at several levels of the primary visual pathway in experimental animals, has been suggested to enhance the encoding of natural scene spectra [25], and/or to optimize the transfer of trichromatic color information [26,27]. By analogy with spatial sinusoids, trichromacy has also been interpreted in terms of comb-filtered spectra [28].…”

language impairment and colour categories

“…Nevertheless, nonuniform distribution of color preferences places constraints on category formation. Similarities between the properties of neurons in the visual system and efficient codes for natural colors (Caywood et al 2004;Lee et al 2002;Wachtler et al 2001) further indicate that color vision is adapted to the statistics of natural chromatic signals, which implies shared categories.…”