Abstract
In congenital color blindness the red–green discrimination is impaired resulting in an increased confusion between those colors with yellow. Our post-receptoral physiological mechanisms are organized in two pathways for color perception, a red–green (protanopic and deuteranopic) and a blue–yellow (tritanopic). We argue that the discrimination losses in the yellow area in congenital color vision deficiency subjects could generate a subtle loss of discriminability in the tritanopic channel considering discrepancies with yellow perception. We measured color discrimination thresholds for blue and yellow of tritanopic channel in congenital color deficiency subjects. Chromaticity thresholds were measured around a white background (0.1977 u′, 0.4689 v′ in the CIE 1976) consisting of a blue–white and white–yellow thresholds in a tritanopic color confusion line of 21 congenital colorblindness subjects (mean age = 27.7; SD = 5.6 years; 14 deuteranomalous and 7 protanomalous) and of 82 (mean age = 25.1; SD = 3.7 years) normal color vision subjects. Significant increase in the whole tritanopic axis was found for both deuteranomalous and protanomalous subjects compared to controls for the blue–white (F2,100 = 18.80; p < 0.0001) and white–yellow (F2,100 = 22.10; p < 0.0001) thresholds. A Principal Component Analysis (PCA) found a weighting toward to the yellow thresholds induced by deuteranomalous subjects. In conclusion, the discrimination in the tritanopic color confusion axis is significantly reduced in congenital color vision deficiency compared to normal subjects. Since yellow discrimination was impaired the balance of the blue–yellow channels is impaired justifying the increased thresholds found for blue–white discrimination. The weighting toward the yellow region of the color space with the deuteranomalous contributing to that perceptual distortion is discussed in terms of physiological mechanisms.
Highlights
Congenital color blindness is a genetic condition in which male subjects show impairment in performing red–green discriminations increasing the confusion between those colors with yellow
We evaluated 82 subjects with normal color vision recruited among the Institute of Psychology of the University of São Paulo students and staff with mean age of 25.1 years (SD = 3.56, 40 males)
Statistical differences were found for protan and deutan (0.0165 u v units; SD = 0.0048) color defect subjects with normal color vision subjects (−0.0005 u v units; SD = 0.0015; F1,101 = 199.71; p < 0.0001) for both blue and yellow distances
Summary
Congenital color blindness is a genetic condition in which male subjects show impairment in performing red–green discriminations increasing the confusion between those colors with yellow. The inputs of the L- and M-cones contribute to another post-receptoral channel in which the S-cone signal is processed opponent to the L and M-cone signals combined – subjects show impairment in performing blue–yellow color discriminations increasing the confusion between those colors with white – called blue–yellow opponency, projecting to visual cortex via Koniocellular (KC) pathway of the LGN (Silveira et al, 1999; Teufel and Wehrhahn, 2000; Szmajda et al, 2006; Roy et al, 2009; Packer et al, 2010). The lines on the CIE color diagram corresponding to the red–green (protan and deutan) and blue– yellow (tritanopic) color opponency are the color confusion axes (Figure 1)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.