The spatio-chromatic sensitivity of the human visual system

The response of the human visual system depends on a multitude of image fea tures, such as the wavelength (colour) of the visual stimulus and its spati al frequency content. Hence we need to take into account the spatial and ch romatic sensitivity as well as spatio-chromatic interactions to properly ch aracterize visual sensitivity. In this paper we report two experiments that further characterize the spatio-chromatic sensitivity of the human visual system for stationary stimuli, namely the detection of small visual orienta tion differences and the detection of blur. In both cases we find that the Visual system is equally sensitive to red-green and to black-white modulati ons for a wide range of spatial parameters. Furthermore, the contrast depen dence for red-green and black-white modulations is identical, suggesting th at the same mechanism mediates both types of stimulus, Our results are in a ccordance with the hypothesis that both tasks are mediated by the parvocell ular as opposed to the magnocellular pathway.