Abstract
Cross-orientation masking occurs when the detection of a test grating is masked by a superimposed grating at an orthogonal orientation, and is widely thought to indicate the presence of "cross-channel" interactions mediating contrast normalization. In achromatic vision, modeling and psychophysical experiments have suggested that there are at least two routes to cross-orientation suppression prior to binocular summation: a within-eye (monocular) pathway that is non-adaptable, and an interocular (dichoptic) adaptable pathway that is cortical and mediates mutual suppression between the eyes (Baker et al., Neuroscience, 146, 2007: Meese & Hess, 2004). Here we develop this two-stage model and test its application to color vision. Test and mask stimuli were red-green isoluminant Gabors presented orthogonally. TvC masking functions were obtained for three spatial frequencies (0.375, 0.75 & 1.5cpd at 2Hz) for monocular, binocular and dichoptic presentations in four subjects. We generalized the two-stage model so that it could be used to fit the monocular, dichoptic and binocular TvC functions. We determined the weight of suppression parameters for the monocular and dichoptic suppression, with the remaining parameters fixed on the basis of known values. We find that the two-stage model is a good fit to the chromatic data, supporting the idea that color and achromatic vision use the same two routes to cross-orientation suppression. The dichoptic pathway shows greater suppression than monocular in color vision. It is also unselective as it can be activated by achromatic or chromatic contrast (Mullen et al., 2012). We find no effect of spatial frequency on either pathway.
Meeting abstract presented at OSA Fall Vision 2012