Perceptual compensation in anomalous trichromats?

[摘要] Anomalous trichromacy is the most common form of color vision deficiency (CVD), wherein one cone class expresses an abnormal photopigment. In anomalous trichromats, this causes decreased discrimination and sensitivity in the red-green dimension of color vision. However, the visual system can recalibrate its outputs based on its inputs through neural adaptation. Thus, long-term adaptation might compensate for decreased red-green inputs. A recent study used unique hue judgments to evaluate the scaling of perceptual color spaces of anomalous trichromats and color normal subjects (Boehm et al., 2014). The CVD subjects in their study had dimensional scaling more similar to color normals than their discrimination thresholds predicted, suggesting a compensatory mechanism. The current study expands upon this research by investigating whether this compensation is present in perceptual contrast matches between stimuli that vary along chromatic and achromatic axes in a cone-opponent space.Subjects were screened for color vision deficiency using pseudoisochromatic plate tests. Those identified as CVD were further classified using Rayleigh matches on a Nagel Anomaloscope. For all subjects, discrimination thresholds, which should be unaffected by cortical compensation mechanisms, were measured using the Cambridge Colour Test. A suprathreshold matching task was used to measure perceptual scaling across axes in a modified DKL space. Test stimuli in this task were 10° gabors modulated along the isoluminant L-M and S-(L+M). Using a staircase procedure, subjects matched the contrast of chromatic gratings to a standard achromatic comparison grating.Preliminary data show a high correlation between discrimination thresholds measured by CCT and suprathreshold contrast matches between L-M stimuli and reference achromatic stimuli, for both color normal subjects and anomalous trichromats. That is, suprathreshold matches are well predicted by threshold measurements. This suggests that the perceptual compensation measured using unique hue judgments may not manifest as changes in scaling of suprathreshold contrast matches.

[学科分类] 眼科学