Statistics of natural scenes and the cortical representation of color

Abstract

In this paper we investigate the spatial correlational structure of orientation and color information in natural images. We compare these with the spatial correlation structure of optical recordings of macaque monkey primary visual cortex, in response to oriented and color stimuli. We show that the correlation of orientation falls off rapidly over increasing distance. By using a color metric based on the a-b coordinates in the CIE-Lab color space, we show that color information, on the other hand, is more highly correlated over larger distances. We also show that orientation and color information are statistically independent in natural images. We perform a similar spatial correlation analysis of the cortical responses to orientation and color. We observe a similar behavior to that of natural images, in that the correlation of orientation-specific responses falls off; more rapidly than the correlation of color-specific responses. Our findings suggest that: (a) orientation and color information should be processed in separate channels, and (b) the organization of cortical color responses at a lower spatial frequency compared to orientation is a reflection of the statistical structure of visual world.