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PubMedDate not supplied

[Color vision as a function of a complex variable].

In the present contribution the algebra of color vision has been developed. This algebra is similar to that of spinors. In this formalism, white color corresponds to zero, and any color on color circle goes to complex number. So the color intensity corresponds to the modulus of complex number, as the color itself is the phase of complex number. The schemes of Young-Helmholtz and Hering have been considered. It is demonstrated that these schemes both generate the same algebra of complex numbers, though projective-geometrical algorithm are different.

Algorithms↗
PubMed2006

Color vision but not visual attention is altered in migraine.

OBJECTIVE: To examine visual search performance in migraine and headache-free control groups and to determine whether reports of selective color vision deficits in migraine occur preattentively. BACKGROUND: Visual search is a classic technique to measure certain components of visual attention. The technique can be manipulated to measure both preattentive (automatic) and attentive processes. Here, visual search for colored targets was employed to extend earlier reports that the detection or discrimination of colors selective for the short-wavelength sensitive cone photoreceptors in the retina (S or "blue" cones) is impaired in migraine. METHOD: Visual search performance for small and large color differences was measured in 34 migraine and 34 control participants. Small and large color differences were included to assess attentive and preattentive processing, respectively. In separate conditions, colored stimuli were chosen that would be detected selectively by either the S-, or by the long- (L or "red") and middle (M or "green")-wavelength sensitive cone photoreceptors. RESULTS: The results showed no preattentive differences between the migraine and control groups. For active, or attentive, search, differences between the migraine and control groups occurred for colors detected by the S-cones only, there were no differences for colors detected by the L- and M-cones. The migraine group responded significantly more slowly than the control group for the S-cone colors. CONCLUSIONS: The pattern of results indicates that there are no overall differences in search performance between migraine and control groups. The differences found for the S-cone colors are attributed to impaired discrimination of these colors in migraine and not to differences in attention.

Attention↗
PubMed1998

Pigment gene expression in protan color vision defects.

We screened 150 male eye donors and identified four who did not have or express L pigment genes, consistent with each of them having a congenital protan color vision defect. One donor was identified as a protanope because he had and expressed a single X-chromosome photopigment gene that encoded an M pigment. Three were categorized as protanomalous because each expressed significant levels of genes specifying two spectrally different M pigments. The first gene in each of the protanomalous arrays was expressed the most and encoded an M pigment that differed in amino acid sequence from M pigments in color normal men.

Base Sequence↗
PubMedDate not supplied

Achromatic parvocellular contrast gain in normal and color defective observers: Implications for the evolution of color vision.

The PC pathway conveys both chromatic and achromatic information, with PC neurons being more responsive to chromatic (L-M) than to achromatic (L+M) stimuli. In considering the evolution of color vision, it has been suggested that the dynamic range of chromatic PC-pathway processing is tuned to the chromatic content of the natural environment. Anomalous trichromats, with reduced separation of their L- and M-cone spectral sensitivities, have diminished chromatic input to PC-pathway cells. Dichromats, with absent L or M cones, should have no chromatic input to PC-pathway cells. Therefore, the PC-pathway dynamic range of color defectives should be released from any constraint imposed by the chromatic environment. Here we ask whether this results in compensatory enhancement of achromatic PC-pathway processing in color defectives. This study employed a psychophysical method designed to isolate PC-pathway processing using achromatic stimuli. In a pulsed-pedestal condition, a four-square stimulus array appeared within a uniform surround. During a trial, one of the test squares differed from the other three, and the observer's task was to choose the square that was different. A four-alternative, forced-choice method was used to determine thresholds as a function of the contrast of the four-square array to the surround. Seven color defective and four normal observers participated. Results showed no systematic differences between normals and color defectives. There was no enhancement of achromatic processing as compensation for reduced chromatic processing in the PC-pathway system in color defectives. From physiological recordings, PC-pathway achromatic contrast gains of dichromatic and trichromatic New World primates and trichromatic Old World macaques have also been shown to be similar to each other. Our study and the animal studies imply that PC-pathway contrast gain parameters were regulated by factors other than the environmental chromaticity gamut, and may have arisen in a nontrichromatic common ancestor to both Old and New World primates.

Animals↗
PubMed1964

VISUAL PIGMENTS IN SINGLE RODS AND CONES OF THE HUMAN RETINA. DIRECT MEASUREMENTS REVEAL MECHANISMS OF HUMAN NIGHT AND COLOR VISION.

Difference spectra of the visual pigments have been measured in single rods and cones of a parafoveal region of the human retina. Rods display an absorption maximum (lambdamax) at about 505 mmicro associated with rhodopsin. Three kinds of cones were measured: a blue-sensitive cone with Amaxe about 450 mpf; two green-sensitive cones with Xmaa about 525 mumicro; and a red-sensitive cone with lambdamax about 555 mmicro These are presumably samples of the three types of cone responsible for human color vision.

Color Perception↗
PubMed2003

Historical contingency in the evolution of primate color vision.

Primates are unique among eutherian mammals for possessing three types of retinal cone. Curiously, catarrhines, platyrrhines, and strepsirhines share this anatomy to different extents, and no hypothesis has hitherto accounted for this variability. Here we propose that the historical biogeography of figs and arborescent palms accounts for the global variation in primate color vision. Specifically, we suggest that primates invaded Paleogene forests characterized by figs and palms, the fruits of which played a keystone function. Primates not only relied on such resources, but also provided high-quality seed dispersal. In turn, figs and palms lost or simply did not evolve conspicuous coloration, as this conferred little advantage for attracting mammals. We suggest that the abundance and coloration of figs and palms offered a selective advantage to foraging groups with mixed capabilities for chromatic distinction. Climatic cooling at the end of the Eocene and into the Neogene resulted in widespread regional extinction or decimation of palms and (probably) figs. In regions where figs and palms became scarce, we suggest primates evolved routine trichromatic vision in order to exploit proteinaceous young leaves as a replacement resource. A survey of the hue and biogeography of extant figs and palms provides some empirical support. Where these resources are infrequent, primates are routinely trichromatic and consume young leaves during seasonal periods of fruit dearth. These results imply a link between the differential evolution of primate color vision and climatic changes during the Eocene-Oligocene transition.

Animals↗
PubMed1992

Molecular basis of congenital color vision defects in Chinese patients.

Applying Southern blot hybridization, the structures of the red pigment gene (RPG) and the green pigment gene (GPG) were analyzed in 43 Chinese patients with red-green color vision defects, including 3 female cases of deuteranopia. The same analysis was carried out in 4 normal relatives and 3 carriers from 3 affected families, as well as in 11 normal controls. Among the 43 patients, abnormalities of the RPG were detected in all 19 protans, and abnormalities of the GPG were found in 14 of the 24 deutans. In about 80% of the protans and deutans, an alteration of exon 5 in RPG or GPG was discovered. All 19 protans had anomalous RPG and in one protan the normal RPG was replaced by a 5' red-3' green hybrid gene. However, no protans showed deletion of the whole RPG. Some deutans had no GPG; some had a 5' green-3' red hybrid gene with or without the GPG. The exon 5 of RPG and GPG was amplified by polymerase chain reaction (PCR) and the amplified fragments were further analyzed by RsaI digestion. The results of PCR were identical to those of nucleic acid hybridization. PCR will be a useful tool in prenatal diagnosis and genetic counseling.

Adolescent↗
PubMed2005

Color vision in marmosets and tamarins: behavioral evidence.

Here we demonstrate differences in the relative performance of 15 callitrichids tested in a series of color visual discrimination experiments. Munsell color chips were chosen as stimuli based on their use in earlier experiments with human dichromats. We show behavioral evidence for the existence of four distinct kinds of color-vision phenotypes, each of which has slightly different color discrimination abilities. The different phenotypes may offer different advantages. The data are in accordance with the existence of a visual polymorphism in callitrichids.

Animals↗
PubMed1995

Association of acquired color vision defects in blue cone monochromatism.

The retinal functions of a 43-year-old man with diabetic retinopathy in a family affected by blue cone monochromatism were studied. While changes in visual acuity and color vision were similar to those seen in patients affected by rod monochromatism, and his spectral sensitivities on high intensity background and his threshold versus intensity curve indicated only suggestive blue cone function, mass electroretinograms (ERG) findings demonstrated well preserved blue cone function. The disparity in blue cone function between psychophysical and mass electroretinographical evaluation may be caused by the difference in how much the fovea influenced each testing. Diabetic retinopathy most likely caused significant reduction of the psychophysical blue cone function and resulted in clinical findings similar to rod monochromatism. The mass blue cone ERG was useful to differentiate blue cone monochromatism from rod monochromatism in this diabetic patient.

Adult↗
PubMed1993

G6PD haplotypes spanning Xq28 from F8C to red/green color vision.

The most telomeric region of the human X chromosome within band Xq28 consists of a gene-rich region of about 3 Mb which contains the genes for coagulation factor VIIIc, glucose-6-phosphate dehydrogenase (G6PD), and red/green color vision. We have studied five polymorphic sites from this region, in a sample of normal people from the Cosenza province of Southern Italy. These sites, which span a distance of some 350 kb, are in strong linkage disequilibrium. Of the 32 possible haplotypes only 10 were found, and 4 of these account for 80% of all X chromosomes analyzed. In addition, we found that all G6PD-deficient people with the G6PD Mediterranean mutation belong to only two haplotypes. One of these (Med 1) is found only within a small subregion of the area investigated, west of the Appennine mountain range. Most remarkably, all Med 1 G6PD-deficient individuals also had red/green color blindness. The more frequent haplotype (Med 2) is the same in Calabria and in Sardinia, where it accounts for about 90% of the G6PD Mediterranean mutations, despite the fact that gene flow between the populations of Sardinia and Southern Italy must have been limited. These data do not enable us to determine whether the two types of G6PD Mediterranean have arisen through two separate identical mutational events or through a single mutational event followed by recombination. However, the data indicate relatively little recombination over an extended region of the X chromosome and they suggest that the G6PD Mediterranean mutation is recent by comparison to the other polymorphisms investigated.

Adult↗
PubMed1998

Color vision in two observers with highly biased LWS/MWS cone ratios.

Two sisters, heterozygous carriers for congenital X-linked protanopia, were diagnosed as normal trichromats by the Rayleigh match on the anomaloscope. The heterozygous state was established by molecular analysis of their visual pigment genes. The normal color match establishes that the spectral sensitivities of their long-wavelength-sensitive (LWS) and middle-wavelength-sensitive (MWS) cone visual photopigments are within normal variability. Their FM 100-hue test error scores were low, demonstrating superior chromatic discrimination. Heterochromatic flicker photometric (HEP) spectral sensitivities were like those of protanopes. The estimated LWS/MWS cone ratios from the HFP data were 0.09/1 and 0.03/1, compared with ratios in the range of 0.6/1 to 10/1 for typical normal trichromats. Measurements of chromatic grating acuity on chromatically selective backgrounds were performed to study the cone mosaic. The data were consistent with a sparsity of LWS cones. Both protan carriers showed normal spectral sensitivities for all three cone types under cone isolating chromatic adaptation and normal three-peaked curves for increment thresholds on a white pedestal. Hue estimation, run on one carrier was normal. The equilibrium yellow locus was measured in the other carrier and was in the range of normal trichromats. The data indicate that normal color vision can occur even when the LWS/MWS cone ratio is quite abnormal.

Adaptation, Ocular↗
PubMedDate not supplied

[Disorders of color vision in employees of the Masovian Refining and Petrochemical Industries in Płock].

Attention is drawn to the problem of the influence of the petrol derivates on the frequency of acquired dyschromatopsia. It has been observed--on the basis of performed examinations of the color vision by means of the Farnsworth-Munsell's 100-Hue test--that the general numerical index of the faults is increasing proportionally to the period of employment, i.s. the period of the contact of the workers with the derivates of petrol.

Adult↗