LAUSR

The lateral geniculate nucleus (LGN) processes cardinal colors but not non-cardinal, while non-cardinal color perception occurs in the visual cortex. As LGN receptive fields are circular, spot stimuli are processed better in the LGN, whereas grating stimuli are processed exclusively in the cortex, where receptive fields are elongated. We thus tested whether gratings better reveal non-cardinal mechanisms. Stoughton et al. (2012) tested this question in the isoluminance plane in macaques, and Gegenfurtner & Kiper (1992) in the red-green/luminance plane in humans. We tested all three color planes, all in humans. The current experiment is an extension of Rodriguez, Dunigan, Powell & Gunther (OSA FVM 2018), testing a larger number of directions in color space. In each color plane, three participants performed noise masking with stimuli in 8 or 12 directions in color space, presented in four masks (two cardinal, two 45 deg non-cardinal). Our data support the hypothesis that gratings better reveal non-cardinal mechanisms than spots do. The data are particularly strong in the tritan/luminance plane, the color plane where this has not yet been tested.