SEARCH · PubMed Health

Results for “Color Perception”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources

PubMedDate not supplied

Color vision sensitivity in normally dichromatic species and humans.

Spectral-sensitivity functions for large, long-duration increments presented on a photopic white background indicate that wavelength-opponent mechanisms mediate detection in both normal and dichromatic humans. Normal humans exhibit high color-vision sensitivity as they discriminate the color of spectral flashes at detection-threshold intensities. However, dichromatic humans require stimuli up to about 0.4 log units above detection intensity to see certain colors. This low color-vision sensitivity in human dichromats may be an abnormal condition involving a defect in postreceptoral color processing. To test this hypothesis, we determined color-discrimination thresholds in normally dichromatic species: chipmunk, 13-lined ground squirrel, and tree shrew. For comparison, we also tested humans with normal and abnormal (deutan) color vision with the same apparatus and methods. Animals were trained to perform spatial two-choice discrimination tasks for food reward. Detection thresholds were determined for increments of white, 460 nm, 540 nm, 560 nm, 580 nm, 500 nm/long-pass, and 500 nm/short-pass on white backgrounds of 1.25 cd/m2, 46 cd/m2, and 130 cd/m2. Animals were also trained to respond to the colored increments when paired with the white increment when both were at equally detectable intensities. Color-discrimination thresholds were determined by dimming stimulus pairs (colored vs. white) until the subjects could no longer make the discriminations. Results indicated that the normally dichromatic species could discriminate colored stimuli from white at a mean intensity of 0.1 (+/-0.1) log units above detection threshold. The ability of normally dichromatic species to discriminate color near detection-threshold intensity is consistent with increment spectral-sensitivity functions that indicate detection by wavelength-opponent mechanisms. In keeping with previous studies, normal human trichromats discriminated color near detection-threshold intensities but humans with deutan color vision required suprathreshold intensities to discriminate the color of middle and long wavelengths. This high color-vision sensitivity of normally dichromatic species suggest that the low color-vision sensitivity in dichromatic humans is an abnormal condition and indicates a possible defect in their postreceptoral color-vision processing.

Animals↗

PubMedDate not supplied

Interactions between rod and L-cone signals in deuteranopes: gains and phases.

The dynamics of interactions between rod and L-cone driven signals were studied psychophysically in two deuteranopic observers. Flicker detection thresholds for different ratios of rod to L-cone modulation were measured at temporal frequencies between 1 and 15 Hz. A model, which assumes that rod and L-cone driven signals are vector added, can describe the threshold data adequately. We found that up to about 8-10 Hz temporal frequency, rod and L-cone signals interact additively, whereas at higher frequencies the interaction is subtractive. Rod and L-cone signal strengths depend similarly on temporal frequency and are maximal between 3 and 5 Hz. The phase difference between rod and L-cone signals increases linearly with temporal frequency, indicating that their responses have a delay difference of about 20 to 30 ms, consistent with involvement of the faster rod pathway. The data would suggest a nearly complete additivity of the rod and cone driven signals when using flashed stimuli. But, literature data showed only partial additivity of the two, suggesting that different postreceptoral mechanisms are involved in the two tasks.

Adult↗

PubMedDate not supplied

Novel form of a single X-linked visual pigment gene in a unique dichromatic color-vision defect.

In normal trichromats, the long- (L) and middle-wavelength-sensitive (M) pigment genes are arranged in a head-to-tandem array on the X chromosome. Two amino acids at positions 277 and 285, encoded by exon 5 of the L and M genes, respectively, are essential for the spectral difference between L and M pigments whose spectral peaks are at approximately 560 and 530 nm. Intragenic or intergenic unequal crossing-over commonly occurs between the highly homologous L and M genes, resulting in red-green color vision deficiencies. The dichromacy is usually associated with a single L gene for deuteranopia or a single 5' L-M 3' hybrid gene with M-gene exon 5 for protanopia. We clinically diagnosed a total of 88 male dichromats using a Nagel model I anomaloscope, which included one unclassified subject in addition to 31 protanopes and 56 deuteranopes. The objective of this study was to characterize the phenotype of the subject and to determine the genotype of his X-linked pigment genes. The subject accepted not only any red-green mixture but also an extended yellow-scale range at each matching point (i.e. 20 to 32 scale units at the green primary and 3.5 to 6 scale units at the red primary). The slopes of regression lines were in the range of -0.34 to -0.23, while the mean slopes for the protanopes and deuteranopes were -0.38 and -0.01, respectively. Spectral sensitivity tests showed that the subject's curve was shifted between the protanope and deuteranope curves. Molecular analysis revealed a novel form of a single pigment gene with a unique arrangement of exon 5 (Y277 from the L gene and A285 from the M gene). The predicted lambdamax (541 to 546 nm) of the unique pigment was closer to the M than to the L pigment. Our outcome suggests that intragenic unequal crossing-over may have occurred between amino acid positions 279 and 283.

Adult↗

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↗

PubMedDate not supplied

A novel mutation in the short-wavelength-sensitive cone pigment gene associated with a tritan color vision defect.

Inherited tritan color vision deficiency is caused by defects in the function of the short-wavelength-sensitive (S) cones. This heterozygous group of disorders has an autosomal dominant pattern of inheritance. Amino acid variations of the S cone opsin are rare and all that have been identified thus far are associated with inherited tritan color vision defects. Here we report the identification of a 30-year-old male who made errors on standard color vision tests consistent with the presence of a mild tritan color vision deficiency. We tested the hypothesis that his color vision impairment was due to a mutation in the S cone photopigment gene. He was found to be heterozygous for a mutation that caused the amino acid proline to be substituted in place of a highly conserved leucine at amino acid position 56 in the S cone opsin. This mutation was absent in 564 S cone photopigment genes from 282 subjects who did not make tritan errors. Thus, we conclude that this mutation disrupts the normal function of S cones.

Adult↗

PubMedDate not supplied

Anomalous trichromats' judgments of surface color in natural scenes under different daylights.

Deuteranomalous trichromacy, which affects medium-wavelength-sensitive cones, is more common than protanomalous trichromacy, which affects long-wavelength-sensitive cones. The aim of the present work was to test the extent to which these two kinds of anomalous trichromacy affect surface-color judgments in the natural world. Simulations of 18 natural scenes under different daylight illuminants were presented on a high-resolution color monitor to 7 deuteranomalous, 7 protanomalous, and 12 normal trichromatic observers, who had to discriminate between reflectance and illuminant changes in the images. Observers' ability to judge surface color was quantified by a standard color-constancy index. Deuteranomalous trichromats performed as well as normal trichromats, but protanomalous trichromats performed more poorly than both. The results are considered in relation to the spectral coverage of cones, rod intrusion, and the characterization of anomalous trichromacy by the Rayleigh match.

Adolescent↗

PubMedDate not supplied

An adaptation of the Cambridge Colour Test for use with animals.

Recently, molecular biological techniques have presented new opportunities for addressing questions concerning the neural mechanisms involved in color coding, thereby rousing renewed interest in animal color vision testing. We have modified a computer-based assessment tool, the Cambridge Colour Test, to make it suitable for use with animals. Here, the validity and reliability of the testing method were evaluated using squirrel monkeys. Because the chromatic stimuli and the achromatic backgrounds of the test consist of dots that vary in lightness, the stimulus parameters can be adjusted so that animals are not able to use luminance differences to make correct discriminations. Thus, in contrast to methods used previously, this test does not require that time be spent equating the luminance of each chromatic stimulus examined. Furthermore, the computer video-display based design of the testing apparatus can be easily replicated and adapted for use with many species in a variety of settings. In the present experiments, the squirrel monkeys' behavioral results agreed with the predictions for their color vision based on genetic analysis and electroretinography (ERG) spectral sensitivity data. Repeated measurements were highly consistent. Thus, an adaptation of the Cambridge Colour Test provides a valid and reliable method for testing color vision in animals.

Animals↗

PubMedDate not supplied

Color naming and categorization in inherited color vision deficiencies.

Dichromatic subjects can name colors accurately, even though they cannot discriminate among red-green hues (Jameson & Hurvich, 1978). This result is attributed to a normative language system that dichromatic observers developed by learning subtle visual cues to compensate for their impoverished color system. The present study used multidimensional scaling techniques to compare color categorization spaces of color-vision deficient (CVD) subjects to those of normal trichromat (NT) subjects, and consensus analysis estimated the normative effect of language on categorization. Subjects sorted 140 Munsell color samples in three different ways: a free sorting task (unlimited number of categories), a constrained sorting task (number of categories limited to eight), and a constrained naming task (limited to eight basic color terms). CVD color categories were comparable to those of NT subjects. For both CVD and NT subjects, a common color categorization space derived from the three tasks was well described by a three-dimensional model, with the first two dimensions corresponding to reddish-greenish and yellowish-bluish axes. However, the third axis, which was associated with an achromatic dimension in NTs, was not identified in the CVD model. Individual differences multidimensional scaling failed to reveal group differences in the sorting tasks. In contrast, the personal color naming spaces of CVD subjects exhibited a relative compression of the yellowish-bluish dimension that is inconsistent with the typical deutan-type color spaces derived from more direct measures of perceptual color judgments. As expected, the highest consensus among CVDs (77%) and NTs (82%) occurred in the naming task. The categorization behaviors studied in this experiment seemed to rely more on learning factors, and may reveal little about CVD perceptual representation of colors.

Adult↗

PubMedDate not supplied

Illuminant and observer metamerism and the Hardy-Rand-Rittler color vision test editions.

A previous study identified a significant metamerism in the several editions of the Hardy-Rand-Rittller pseudoisochromatic plates (HRR) but did not proceed to quantify the consequences of that metamerism (Dain, 2004). Metamerism arises from two sources and is almost inevitable when a printed color vision test is reproduced in several editions. Metamerism has two consequences; these are illuminant/source-based changes in performance and changes in performance with observer (less well known) when assessing anomalous trichromats. This study addresses the effects of illuminant/source and observer metamerism on the fourth editions of HRR. Groups of colors intended to lie on a dichromat confusion line generally remain on a confusion line when the source id changed. The plates appear to be resistant to each form of metamerism, perhaps because the features of the spectral reflectance are similar for figure color and background gray. As a consequence, the clinician needs to be less concerned about using a non-recommended source than was previously believed.

Color Perception↗

PubMed2001

Towards a model to predict macular dichromats' naming errors: effects of CIE saturation and dichromatism type.

Thirty macular dichromat children (12 protanopes + 18 deuteranopes) and 29 controls, between 5 and 9 years old, participated in a monolexemic denomination task. Their clinical status was determined after a repeated application of a chromatic test set (Ishihara, CUCVT, and TIDA). The stimuli to be named were 12 tiles from the Color-Aid set belonging to the green, blue, and purple basic categories. Results showed that: (a) Dichromats made more naming errors when low saturation stimuli were used; (b) protanopes made more errors that deuteranopes; and (c) pseudoisochromatic lines predicted accurately the type of most frequent naming errors but they underestimated macular dichromats' functional capacity to name colors. Results are consistent with a model of macular dichromats' vision that hypothesizes a residual third type of cone in the periphery of the retina. Implications of this fact for everyday use of colors by macular dichromats' and for the validity of standard clinical diagnoses are discussed.

Child↗

PubMed2003

Detecting color vision in a malingerer.

A patient describing himself as totally color blind was ordered by the judicial system to have his color vision investigated in order to establish his suitability for military service. Basic clinical (Farnsworth Panel D-15, Moreland and Rayleigh anomaloscope equations), electroretinographic (ERG) and psychophysical techniques (spectral sensitivities) were applied to determine the extent of his color discrimination performance and cone function. These standard procedures were complemented by a test for cone interaction (transient tritanopia) and by newly developed cone-isolating flicker large-field ERG recordings. The patient's data consistently indicate the function as well as the functional interaction of the middle-wavelength-sensitive (M-) and the short-wavelength-sensitive (S-) cones. But the function of the long-wavelength-sensitive (L-) cones was completely absent. Hence the patient was correctly demonstrated to be a protanope. This study establishes that standard classical procedures, in combination with newly developed and easy to apply psychophysical and ERG ones, which can be reliably used to assess true color discrimination performance, in difficult cases of malingering.

Adult↗

PubMed2002

Progress of visual dysfunction in Parkinson's disease.

Studies on progression of Parkinson's disease (PD) mainly focus on the nigrostriatal dopaminergic decline, but not on the visual system. We determined progression of (i) disturbed color vision, assessed with the Farnsworth-Munsell 100 Hue test (FMT) and (ii) intensity of PD in 18 patients. Significant differences occurred between (i) initial FMT error scores and follow-up results 3 years later (P=0.002) and analogously (ii) scored intensity of PD (P=0.002). A relation between computed differences of FMT error scores and rated activities of daily living appeared. Deterioration of color vision progresses in PD.

Color Perception↗

PubMed2000

The luminance fall in anomaloscope examination: clinical examples.

PURPOSE: The evaluation of the anomaloscope slope quotient in patients with acquired colour vision deficiency. METHODS: Two patients with Stargardt's disease in combination with protanomaly and deuteranomaly, respectively, were selected and also 3 patients with a presumed dominant optic atrophy of the protan type. The anomaloscope examination was performed according to the Linksz procedure. The luminance fall was calculated as the slope quotient SQ:Y units luminance fall per X units width of the matching range. RESULTS: The SQ of the 2 Stargardt patients was steeper than the SQ of congenital colour vision defectives, especially at the red end of the anomaloscope green-red mixture scale, indicating pathologic scotopization superimposed on the congenital deficiency. In optic atrophy of the protan type the SQ was flatter than in congenital deficiency, indicating that this deficiency has nothing to do with congenital protan deficiency. CONCLUSION: Calculation of the slope quotient SQ is helpful for the diagnosis of acquired colour vision deficiency, especially when the subject also has a congenital colour vision deficiency or is supposed to have such a deficiency.

Adult↗

PubMed2000

Quantitative anomaloscopy and optical coherence tomography scanning in central serous chorioretinopathy.

BACKGROUND: Dyschromatopsia is a prominent sign in a variety of central retinal diseases, such as central serous chorioretinopathy (CSC). The changes in colour vision may be due to either optical or neuronal factors in the diseased retina. The relative contribution from the two causes is unknown, but may be elucidated by obtaining knowledge of the anatomical derangement in the diseased retina in CSC. METHODS: Twenty-six normal persons had their colour vision tested using the Tomey anomaloscope. The calculation of setting range (SR) and central mean point (CMP) for Rayleigh match and Moreland match was optimized, and normal ranges for these values were defined. Subsequently 24 patients with CSC were examined by anomaloscopy and optical coherence tomography scanning, and the measures of colour vision were related to the anatomical changes observed on the scans. RESULTS: The algorithm for calculating SR and CMP which is integrated into the Tomey anomaloscope could be considerably improved to increase sensitivity and reproducibility of these measures. Fifteen patients had abnormal colour vision. Nine patients had pseudo-protanomaly, seven patients had pseudo-tritanomaly, and three patients had abnormalities in both matches. There was no relation between these colour vision abnormalities and the anatomical derangement as seen by OCT in the diseased central retina. CONCLUSION: The findings argue against the notion that the density of retinal cell nuclei, the orientation of photoreceptors, or the size of the central serous detachment are related to the colour vision abnormalities in CSC. The question of whether these abnormalities are due to optical or neuronal factors remains open.

Adult↗

PubMed1991

Colour contrast sensitivity changes caused by peripheral retinal laser photocoagulation.

Macular phototoxicity is known to occur with laser use, and there is evidence that the wavelength of the light used influences this effect. In this study, a computer based colour contrast sensitivity test was used to assess the immediate macular effects of photocoagulation of peripheral flat retinal holes in otherwise normal retinas, using blue-green (488 and 514 nm), yellow (577 nm), orange (595 nm) or red (647 nm) laser light. The laser aiming beam was not allowed to traverse the macula at any stage during treatment. No protan or deutan axis threshold changes were noted in the 17 patients tested irrespective of the laser wavelength used. Tritan axis sensitivity was significantly reduced one hour after treatment with the blue-green laser, but no tritan axis change was found after treatment with longer wavelength lasers. The effect was no longer present the day after treatment in the subjects tested. The results show that even peripheral retinal treatment with blue-green laser can cause acute macular phototoxicity.

Color Perception↗

PubMed1996

A new colour vision test for clinical use.

Several tests are available for assessing colour vision but they can be expensive, complicated or too time consuming to perform. We have produced a new plate test based on pseudoisochromatic principles. The test, using an error score, examines both the red-green and blue-yellow axes, with four levels of difficulty for each axis. Results from a pilot study show that error scores from congenital red-green blind subjects are significantly higher than those of age-matched controls (p < 0.01) only when using the red-green plates and not the blue-yellow plates. In optic neuritis patients, error scores using both the red-green and blue-yellow plates were significantly higher than those of controls throughout the 6 month follow-up. The test, including scoring, takes 6 minutes to complete. These preliminary results suggest that the new test is effective for screening congenital red-green blindness and monitoring colour vision defects in acquired diseases such as optic neuritis.

Adult↗

PubMed1997

Luminance contrast and colour contrast related errors in pseudoisochromatic plate identification.

PURPOSE: To determine whether differences in luminance contrast and colour contrast are factors in failing to identify American Optical pseudoisochromatic plates (AOPP). METHODS: We studied two groups of subjects. In 20 normal test subjects with no errors on the AOPP we used cross-polarising filters to darken and then gradually increase perceived luminance of the AOPP until these normal subjects correctly identified the plate. In a second group, to evaluate the relationship between a luminance contrast sensitivity score using Arden plates and AOPP identification, we tested 37 non-colour-deficient subjects who missed zero to five of the AOPP of low colour and luminance contrast (plates 9-12, 15). RESULTS: Using the cross-polarising filters, we found five plates that required more light to identify (plates 9-12, 15). In the second experiment, we found a significant relationship between the number missed of these five AOPP plates and a decrease in contrast sensitivity (r = 0.91, p < 0.001, Spearman correlation coefficient). CONCLUSION: Errors in AOPP colour plate detection may be due to loss of ability to perceive colour contrast and possibly luminance contrast.

Adult↗

PubMed1998

Colour blindness.

The physiology of colour vision is discussed; as is the way in which the human eye can detect various combinations of red, green and blue. Red-green colour blindness, with X-linked inheritance, is the most common, but other types are also considered. Methods of testing relating to the age of the child are reviewed. The use of colours in teaching is widespread, but there is controversy over the difficulties this may cause a colour blind child. A review of the literature does not reveal much information on this, and any problems that do arise are likely to be individual to the child, and to depend on such factors as overall intelligence, the attitude of the teacher, and the personality of the child. There is not doubt that it is essential to recognise colour vision defects when it comes to choosing a career, and that tests must be done during secondary schooling, but in order to avoid some affected children being disadvantaged there is enough evidence to support testing at school entry.

Child↗