title: Analysis of red/green color discrimination in subjects with a single X-linked photopigment gene.
abstract: 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.
authors.affiliation: Department of Psychology, University of Washington, Seattle 98195-1525, USA. mikro@u.washington.edu
authors.forename: M A
authors.initials: MA
authors.lastname: Crognale
authors.forename: D Y
authors.initials: DY
authors.lastname: Teller
authors.forename: T
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: A G
authors.initials: AG
authors.lastname: Motulsky
authors.forename: S S
authors.initials: SS
authors.lastname: Deeb
mesh_terms: D000221:Adaptation, Ocular; D000293:Adolescent; D000328:Adult; D000368:Aged; D003118:Color Perception / Q000235:genetics*; D003119:Color Perception Tests; D003117:Color Vision Defects / Q000235:genetics*; D004311:Double-Blind Method; D004596:Electroretinography / Q000379:methods; D006801:Humans; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D011601:Psychophysics / Q000379:methods; D012168:Retinal Pigments / Q000235:genetics*; D014960:X Chromosome
chemical_list: D012168:Retinal Pigments