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PubMed1991

The contribution of color to motion in normal and color-deficient observers.

By opposing drifting luminance and color gratings, we have measured the "equivalent luminance contrast" of color, the contribution that color makes to motion. We found that this equivalent contrast was highest (greater than 10%) for low spatial and temporal frequencies and was higher for red/green than for blue/yellow stimuli. Equivalent luminance contrast was about 4% for a green/purple stimulus that fell along the tritan confusion line, indicating a modest input to the motion pathway from the short wavelength-sensitive cones (B-cones). Contrast thresholds for the discrimination of the direction of motion showed that the contribution of color to motion was about the same (within a factor of 2) as that for luminance in terms of multiples of threshold contrast. These responses to moving, chromatic gratings could be mediated by any of several factors that can create a residual response in a luminance pathway: temporal phase lag between the responses to the colors of the stimuli, second harmonic distortion in the response and variability in equiluminance points across units. Each of these factors was evaluated experimentally and their combined effect could account for only a small portion of the contribution of color to motion. As a result, we attribute the perception of the motion of equiluminous stimuli to an opponent-color input to directionally selective cortical units. Chromatic stimuli had little or no equivalent contrast for color-deficient observers, whether the stimulus was red/green, which they discriminate less well than normals, or blue/yellow, which they discriminate almost as well as normals. The equivalent contrast measure provided an excellent basis for classifying normal, protan and deutan observers.

Color↗

PubMed1992

Isoluminant stimuli may not expose the full contribution of color to visual functioning: spatial contrast sensitivity measurements indicate interaction between color and luminance processing.

Visual performance is greatly impaired when tested with heterochromatic isoluminant stimuli. It is thus concluded that the chromatic system contribution to many visual tasks is limited. We suggest that unless color and luminance are shown to be processed independently, such experiments do not demonstrate shortcomings of the chromatic system but rather the inadequacy of using isoluminant stimuli for isolating that system. We hypothesize that color vision has evolved not only to encode color per se but also to enhance luminance-based visual processing, so that for color information to be fully effective, luminance as well as chromatic variations should be present in the stimulus. The hypothesis was tested by studying the contribution of color to spatial vision. The human contrast sensitivity function (CSF) was studied using luminance, isoluminance (color) and combined luminance/color sinusoidal gratings. It is found that luminance contrast sensitivity is enhanced when luminance contrast is accompanied by color contrast and vice versa. The nature of the interaction is best described by an additive single analyzer model. Color opponent cells which respond to both chromatic and achromatic stimuli may be identified as the analyzer.

Color Perception↗

PubMed1988

Internal representations and the conceptual operation of color in pure alexia with color naming defects.

This research examined the structure of internal representation and the conceptual operation of color in two pure alexic cases (Case I and Case II) with color naming defects. Experiment I investigated the structure of the internal representation of different kinds of colors using a similarity judgment task. Experiment II examined categorical judgments of perceived colors using a two-alternative-forced choice task. Experiment III tested the classification of perceived colors using a color sorting task. The performance of Case I essentially fell within the normal range while the results of Case II showed some impairment in the conceptual operation of color. Analysis of the responses obtained from these experiments indicated that the color naming defects in Case I can be explained in terms of visual-verbal disconnection. However, the naming defects in Case II reflect disfunction in some other higher cortical processes coupled with visual-verbal disconnection.

Color Perception↗

PubMed1987

Color discrimination by the cotton-top tamarin (Saguinus oedipus oedipus) and its relation to fruit coloration.

Old World monkeys and apes have been reported to differ from New World monkeys in their abilities to discriminate colors across the visible spectrum. Old World monkeys and apes (Macaca, Pan, Pongo) discriminate colors quite accurately, while some New World monkeys studied (Saimiri, Cebus) have shown lower sensitivity to and poorer discrimination of long wavelength light. This study examined the color discrimination ability of another New World primate, the cotton-top tamarin, Saguinus oedipus oedipus (family Callitrichidae). The tamarins were trained to discriminate a set of Munsell color chips, both within the same hue category and from the 2 hue categories on either side of the training hue. Results indicated that the cotton-top tamarin can make accurate discriminations across the visible spectrum. Human subjects were tested under similar conditions in order to compare their color discrimination abilities to those of the tamarins. The tamarins and human subjects had the most difficulty discriminating the same hues. The discrimination abilities of the monkeys were assessed in relation to the coloration of fruits eaten in a natural environment. A list of the species of fruits commonly eaten by various species of New World monkeys was compiled and the coloration of fruits at maturity was noted. It was found that most New World primate species eat fruits whose mature coloration ranges across most of the spectrum.

Adolescent↗

PubMed1989

Effects of luminance contrast on color spreading and illusory contour in the neon color spreading effect.

The present study examined whether color spreading and illusory contours in the neon color spreading effect of Ehrenstein figures are governed by different mechanisms. In the experiment, Ehrenstein figures with colored crosses inserted in the central gaps were used. There were three luminance conditions: the luminance of the Ehrenstein figures was lower than, the same as, or higher than the luminance of the background. In each condition, 16 trials (2 sets of instructions X 8 repetitions) were conducted in a random order. Subjects were required to adjust the luminance of the colored crosses according to one of the two sets of instruction given before each trial. One was to adjust the upper and lower thresholds in the luminance of the colored crosses such that their color was seen to spread out of the crosses. The other was to adjust the thresholds such that circular illusory contours were visible. It was found that illusory contours disappeared and the color spreading remained when the crosses and the Ehrenstein figures were in or nearly in isoluminance or when the Ehrenstein figures and the background were in isoluminance. These results suggest that color spreading and illusory contours are governed by different mechanisms.

Adult↗

PubMed1983

Limited improvement of color deficient vision with colored filters.

For over a hundred years, colored filters have helped people with less than normal color vision, to discriminate colors. Filtered light does not restore missing or abnormal pigments within the defective eye. Contrast and discrimination provided by a suitable colored filter can help discrimination of a given set of colors, but may prevent seeing other sets of colors. The use and limitations of color filters are described as aids for color deficient vision.

Color Vision Defects↗

PubMed1986

The ability of protan color defectives to perform color-dependent air traffic control tasks.

Air traffic controllers perform a variety of tasks which require them to identify, discriminate and name colors. Qualification standards for this occupation require applicants to have normal color vision. Although the validity of this standard has been questioned, Adams and Tague recently presented evidence in this Journal (1985;62:744-50) that protanopes cannot perform color-dependent air traffic control tasks reliably. In our study, the results of 7 severe and 2 moderate protans are compared to those of 78 normals on a set of tasks which simulated critical tasks performed daily by air traffic controllers. The four tasks included discriminating red from black pencil marks on flight progress strips, color-naming of 1(0) and 0.1(0) discs, and identification of colored line segments embedded in a multi-colored background. The severe protans we tested performed none of the tasks as well as normals. While the performance of the moderate protans was better, statistical conclusions could not be drawn. Our set of tasks bears many similarities to the set used by Adams and Tague and it appears we were trying to answer the same questions. The results of the two studies are similar and the conclusions are the same: severe protans cannot perform color-dependent air traffic control tasks reliably.

Accidents, Aviation↗

PubMed1987

Major genes of eye color and hair color linked to LU and SE.

Eye color and hair color were studied in a large Danish family material, tested earlier for a comprehensive set of genetic marker systems. We found strong evidence for linkage of "green eye color" or GEY to the Lutheran-Secretor systems (combined lod score 9.19). This would appear to identify a major gene with influence towards "green eye color". We also found evidence for linkage of GEY to "brown hair color" or BRHC (lod score 5.06), which would appear to identify a second major gene influence in the same region of chromosome 19. Concerning the obvious association in the general population between eye color and hair color which could imitate linkage if it were reflected within sibships, we did not recognize any such intrafamilial association; in the pooled informative sibships GEY and BRHC were independently distributed (as were LU-SE and GEY).

ABO Blood-Group System↗

PubMed1985

Color blindness and Rorschach color responsivity.

Color vision deficits occur in 10% of the American white male population. Thus, color blindness may invalidate diagnostic hypotheses generated from Rorschach data. The Rorschach protocols of 43 white, college male color-blind subjects were compared to the protocols of normally sighted controls. The color-blind group manifested fewer pure "C" responses. No significant between group differences emerged for any of the other primary Rorschach color variables. Pure "C" responses rarely figure prominently in Rorschach evaluations, and the apparent lowered frequency of these responses by the color-blind is insufficient to warrant modification of current Rorschach practice. The data suggest that color blindness is unlikely to confound Rorschach assessment.

Adult↗

PubMed1988

Molecular basis of abnormal red-green color vision: a family with three types of color vision defects.

The molecular nature of three different types of X-linked color-vision defects, protanomaly, deuteranomaly, and protanopia, in a large 3-generation family was determined. In the protanomalous and protanopic males the normal red pigment gene was replaced by a 5' red-3' green fusion gene. The protanomalous male had more red pigment DNA in his fusion gene than did the more severely affected protanopic individual. The deuteranomalous individual had four green pigment genes and one 5' green-3' red fusion gene. These results extend those of Nathans et al., who proposed that most red-green color-vision defects arise as a result of unequal crossing-over between the red and green pigment genes. The various data suggest that differences in severity of color-vision defects associated with fusion genes are caused by differences in crossover sites between the red and green pigment genes. Currently used molecular methodology is not sufficiently sensitive to define these fusion points accurately, and the specific color-vision defect within the deutan or protan class cannot be predicted. The DNA patterns for color-vision genes of female heterozygotes have not previously been described. Patterns of heterozygotes may not be distinguishable from those of normals. However, a definite assignment of the various color pigment gene arrays could be carried out by family study. Two compound heterozygotes for color-vision defects who tested as normal by anomaloscopy were found to carry abnormal fusion genes. In addition, a normal red pigment gene was present on one chromosome and at least one normal green pigment gene was present on the other.(ABSTRACT TRUNCATED AT 250 WORDS)

Blotting, Southern↗

PubMed1987

Color performance of video endoscopes: quantitative measurement of color reproduction.

We have conducted a study aimed at testing the color performance of video endoscopes in quantitative terms for the first time. The video endoscopes investigated were from Fuji, Olympus, Toshiba/Machida, and Welch-Allyn. The tests were carried out with an opto-electronic color analyser using standardized color charts and a neutral grey chart. Hue and chroma of the reproduced colors were measured. The Olympus video endoscope reproduces the hue very well, showing only slight color desaturation. The Fuji video endoscope had a yellowish tint, whereas the picture obtained with the WA video endoscope produced an inhomogeneous picture with a pronounced red/purplish cast at the top of the screen and almost neutral reproduction at the lower half. The Toshiba video endoscope was the only one with a color chip, and reproduced hue fairly well, but its colors were weakly saturated.

Color↗

PubMedDate not supplied

Fox colors in relation to colors in mice and sheep.

Color inheritance in foxes is explained in terms of homology between color loci in foxes, mice, and sheep. The hypothesis presented suggests that the loci A (agouti), B (black/chocolate brown pigment) and E (extension of eumelanin vs. phaeomelanin) all occur in foxes, both the red fox, Vulpes vulpes, and the arctic fox, Alopex lagopus. Two alleles are postulated at each locus in each species. At the A locus, the (top) dominant allele in the red fox, Ar, produces red color and the corresponding allele in the arctic fox, Aw, produces the winter-white color. The bottom recessive allele in both species is a, which results in the black color of the silver fox and a rare black color in the Icelandic arctic fox when homozygous. The B alleles are assumed to be similar in both species: B, dominant, producing black eumelanin, and b, recessive, producing chocolate brown eumelanin when homozygous. The recessive E allele at the E locus in homozygous form has no effect on the phenotype determined by alleles at the A locus, while Ed, the dominant allele is epistatic to the A alleles and results in Alaska black in the red fox and the dark phase in the arctic fox. Genetic formulae of various color forms of red and arctic fox and their hybrids are presented.

Alleles↗

PubMed1992

Skin color measurements in terms of CIELAB color space values.

The principles of color measurement established by the Commission International d'Eclairage have been applied to skin and the results expressed in terms of color space L*, hue angle, and chroma values. The distribution of these values for the ventral forearm skin of a sample of healthy volunteers is presented. The skin-color characteristics of a European subgroup is summarized and briefly compared with others. Color differences between individuals were identified in terms of one, two, or all three color-space parameters. Because the method is quantitative and the principles internationally recognized, these color-space parameters are proposed for the unambiguous communication of skin-color information that relates directly to visual observations of clinical importance or scientific interest.

Adult↗

PubMed1989

Lateralization differences for color-naming and color-matching in men and women.

The relationship between accuracy of color-naming and color-matching in both visual fields (LVF and RVF) as a function of sex was investigated. Subjects were 19 men and 15 women who ranged in age from 18 to 32 yr. Each subject was tested on both a color-naming task and a color-matching task presented tachistoscopically. Accuracy measures for each task were obtained separately for both left and right visual fields. A two-factor analysis of variance with repeated measures on one factor followed by a t test for simple main effects showed significant right visual-field advantage for the color-naming task, a significant sex main effect for the color-matching task (in the left visual field only), and a significant interaction of sex by visual field for the matching task. Men performed in a more strongly lateralized fashion on the color-matching task than did women, supporting the notion of greater lateralization among males.

Adolescent↗

PubMed1978

Dichromatic color language: "reds" and "greens" don't look alike but their colors do.

When protanopes or deuteranopes arrange the Farnsworth Dichotomous Test colors in order of similarity, they reveal their lack of red/green hue discriminations by alternating chips that the normal trichromat sees as reddish and greenish test colors. The dichromatic orderings follow a systematic variation in saturation of blue hues through neutral and into yellow hues as described by theory for each of the two types. Some dichromats who show the typical test behavior nevertheless use reddish and greenish hue terms appropriately when instructed to name the same test colors. Lightness cues are probably used by these dichromats in the naming task but ignored in the perceptual similarity task. Thus, unlike normal trichromats, who use similar names for perceptually similar colors, dichromats may use dissimilar names for perceptually similar colors. In this way they can achieve concordance with the normative language system despite its discordance with their impoverished color perceptions.

Color Perception↗

PubMed1985

A comparison of the analyses of EEG and evoked potentials using colored bars in place of colored heads.

Multichannel EEG and evoked potentials can be re-represented as collections of colored bars, with each bar corresponding to a line of data. These colored bars can be assembled into montages, just like conventional lines of data. Changes in potentials can be followed over space and time by visual inspection of patterns of color. Analogous montages of colored bars can be made with power spectra of EEG and evoked potentials. Colored bars can be visually analyzed more quickly than collections of colored heads, whether or not the heads are cartooned.

Color↗

PubMed1986

Visual event-related potentials to colored patterns and color names: attention to features and dimension.

Four right-handed males and 4 right-handed females were instructed to match pairs of stimuli (colored flashes with either colored patterns or color names) presented sequentially to the central retina. Subjects were to respond to the second stimulus of a pair when it matched the first stimulus in terms of sensory color or word meaning. ERPs recorded from the second stimulus of a pair over occipital and frontal cortical regions indicate the following: Interdimension effects reflect an early and more global discrimination process between colored patterns and word patterns per se. The source of this effect appears to be localized in occipital cortical regions. Intradimension effects were evident later in time and reflect a more refined discrimination process between particular features within a dimension rather than between dimensions. The intradimension color effect began earlier in time than the word effect (229 msec versus 318 msec in the occipital data) and appears to be localized in posterior temporal regions. The onset of the word effect appears to have two neural generators: an early effect localized in frontal regions (274 msec) and a later effect localized in occipital regions (318 msec). The hierarchical model of language processing seems to hold true predominantly in posterior cortical regions. Effects associated with linguistic processing were evident in frontal regions before effects were noted in the occipital regions. This result suggests that either: word information is processed simultaneously and independently in the different regions, or anterior regions feedback onto posterior regions and, therefore, influence the processing in this region.

Adult↗

PubMed1985

Cone mechanisms underlying the color discrimination of deutan color deficients.

An alternation method of color matching was used to obtain a series of extended Rayleigh matches from several deutan color deficients with varying degrees of color discrimination. With large stimulus fields there were differences in the matches made by observers with good color discrimination and the matches made by observers with poor color discrimination. The matches made by observers with poor discrimination could not be modeled with normal cone action spectra. When the field size was reduced the matches of all observers were quite similar and could be modeled with two cone action spectra that were normal in shape and separated by approximately 5 nm. Results suggest that individual differences in ability to discriminate color among deutan observers are not solely related to differences in the cone action spectra.

Adolescent↗