Analysis of red/green color discrimination in subjects with a single X-linked photopigment gene

• Published in: Vision research (Oxford) Vol. 39; no. 4; pp. 707 - 719
• Main Authors: Crognale, M.A, Teller, D.Y, Yamaguchi, T, Motulsky, A.G, Deeb, S.S
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.02.1999; Elsevier Science
• Subjects: Adaptation, Ocular; Adolescent; Adult; Aged; Behavioral psychophysiology; Biological and medical sciences; Color deficiencies; Color Perception - genetics; Color Perception Tests; Color vision; Color Vision Defects - genetics; Double-Blind Method; Electroretinogram; Electroretinography - methods; Flicker ERG; Fundamental and applied biological sciences. Psychology; Genetics; Humans; Male; Middle Aged; Miscellaneous; Photopigments; Polymerase Chain Reaction; Polymorphism, Single-Stranded Conformational; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Psychophysics - methods; Rayleigh matches; Retinal Pigments - genetics; X Chromosome; Rayleigh matches; Color vision; Electroretinogram; Flicker ERG; Color deficiencies; Photopigments; Genetics; Electroretinography; Human; Visual pigment; Photoreceptor; Electrophysiology; Retina; Psychophysics; Gene expression; Wavelength; Eye; Visual system; Visual stimulus; Perception; Stimulus discrimination
• ISSN: 0042-6989; 1878-5646
• DOI: 10.1016/S0042-6989(98)00140-0

Many subjects despite having only a single X-linked pigment gene (single-L/M-gene subjects) are able to make chromatic discriminations by Rayleigh matching, especially when large fields are used. We used a combination of psychophysics (Rayleigh match), electroretinograms (ERG), and molecular genetic techniques to rule out several possible explanations of this phenomenon. Use of rods for chromatic discrimination was unlikely since strong adapting fields were employed and the large-field match results were not consistent with rod participation. A putative mid- to long-wavelength photopigment that escapes detection by current molecular genetic analysis was ruled out by finding only a single L/M photopigment in flicker ERGs from 16 single-L/M-gene subjects. Large-field match results were not consistent with participation of S cones. Amino acid sequence polymorphisms in the S-pigment gene that might have shifted the S cone spectrum towards longer wavelengths were not found on sequencing. The mechanism of chromatic discrimination in the presence of a single photopigment therefore remains unknown. Further possible explanations such as variations in cone pigment density and retinal inhomogeneities are discussed.