Middle- and long-wavelength discrimination declines with rod photopigment regeneration

Hue-discrimination functions were derived from hue-naming data (480-620nm, 20nm steps) obtained in 4 min intervals from 4 min to 28 min postbleach at 10 degrees temporal retinal eccentricity. Hue-naming data were also obtained in the fovea. Hue-discrimination functions derived at the 4, 8, and 12 min intervals were very similar to those derived in the fovea. As time postbleach exceeded 12 min and rod sensitivity increased, the shape of the hue-discrimination functions changed. Most notably, the minimum between 560-580nm disappeared and the just noticeable differences (JNDs) for the longer wavelength stimuli increased. The long-wavelength suppression in hue discrimination may be due to rod input in the magnocellular pathway interacting and affecting the long-wavelength sensitivity of the parvocellular pathway. (C) 2011 Optical Society of America