Effects of light and dark adaptation of rods on specific-hue threshold.
Specific-hue threshold as a function of absolute rod threshold was measured with long-, middle-, and short-wavelength monochromatic test lights presented 17 deg extrafoveally. The measurements were obtained both during the rod phase of long-term dark adaptation and under conditions where the rod receptor system was gradually light adapted from a dark-adapted state by a scotopic background field of increasing retinal illumination. The results show that change in specific-hue threshold with change in absolute rod threshold is not, in general, identical for light and dark adaptation of the rod receptor system. Thus, in the long- and middle-wavelength test regions, the specific-hue threshold could be obtained at higher intensities under the light- as compared to the dark-adaptation condition when absolute rod thresholds were the same. Just the opposite was found for the short-wavelength tests. It is concluded that change in specific-hue threshold with light and dark adaptation of the rod receptor system is not, in general, controlled by the same mechanism.
Department of Psychology, University of Oslo, Box 1094, Blindern, N-0317 Oslo, Norway. kirsten.stabell@epilepsy.no
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Bjørn
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D003118:Color Perception / Q000502:physiology*; D003623:Dark Adaptation / Q000502:physiology*; D005556:Form Perception / Q000502:physiology; D006801:Humans; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology