Color Discrimination Research Articles

Visual dysfunction in patients with idiopathic rapid eye movement sleep behavior disorder

ObjectiveVisual dysfunction is a common feature in α-synucleiopathies but rarely assessed in patients with idiopathic rapid eye movement sleep behavior disorder (iRBD). The current study is set to investigate the comprehensive visual function in iRBD as compared to patients of Parkinson’s disease (PD) with RBD. MethodsEighty-three iRBD subjects diagnosed with polysomnograph (PSG), 52 early PD patients (Hoehn-Yahr stages<3) with RBD symptom prior to onset of motor symptoms and 79 healthy controls without RBD diagnosed based on RBD Questionnaire-Hong Kong (RBDQ-HK) were enrolled in this study. Visual function including color discrimination, stereopsis function, visual illusion (VI) or hallucination (VH) were assessed in addition to UPDRS, Purdue Pegboard test (PPT) and cognitive tests. ResultsAbnormal color discrimination and stereopsis were presented significantly higher in both iRBD and PD patients as compared to controls and more severe in PD than in iRBD. Color discrimination was decreased in all four color in PD patients but not green color in iRBD subjects. Stereopsis test was abnormal in both iRBD and PD, but the proportion of subjects with abnormal stereopsis was significantly higher in PD patients (69.6% vs 42%). Similar number of subjects with iRBD and PD were presented with illusion but only PD patients reported more hallucination. Changes of visual function were associated with age and cognition in both iRBD and PD subjects but was also affected independently by disease duration and clinical stage or fine motor function in PD. In addition, decreased fine motor function demonstrated by PPT was also observed in some iRBD subjects. ConclusionOur results demonstrated comprehensively that visual dysfunction was present in iRBD subjects similar but in a less degree of severity to PD patients, and associated with age, cognition and motor deficit. Whether or not it can be useful in predicting iRBD conversion to PD warrants further investigation.

Assist device in color discrimination using Heilmeier type guest‐host liquid crystal for red‐green color vision defect

AbstractFor assist in color discrimination of color vision defects, the method of observing objects through colored filter has been known. If red filter, which absorbs mostly all light except red light, is used, only the red objects can be highly visible. In this paper, a Heilmeier type guest‐host liquid crystal device with magenta dye was applied to a filter type assist device for red‐green color vision defect. This device can easily control transmittance of green light by changing applied voltage, and make green objects perceived to flicker synchronously. The subjective appraisal of the assist device in color discrimination was performed by five participants with normal vision using a constructed experimental system using a video camera and a PC with a vision simulator. For the confusion indices of the Panel D‐15 test, the effect of the device was statistically significant at P &lt; .01. Moreover, a participant with color vision deficiency assessed it and got results without color confusion on the Panel D‐15 test.

A smoke segmentation algorithm based on improved intelligent seeded region growing

SummaryImage segmentation method based on region growing has the advantages of simple segmentation method and complete segmentation target. Because the color discrimination and gray gradient of smoke are not obvious, the traditional region growing segmentation method is difficult to separate it from the image, resulting in an unsatisfactory segmentation effect. To solve this problem, this paper partially improved the region growing method and proposed a new smoke segmentation algorithm based on the improved intelligent seeded region growing (IISRG) method. First, smoke images obtained from experimental videos were converted from the RGB color space to the HSV color space, and image binarization was achieved using background subtraction with an adaptive threshold in the V channel. Then, a pixel in the binary image was selected intelligently as the seed point, which was used for the regional growth. The final smoke segmentation images were obtained by the morphological processing of region growing images. Experimental smoke segmentation results show that the proposed algorithm has a higher overlap rate and a lower overflow rate, and performs a better smoke segmentation effect compared with the other two approaches. In addition, this algorithm can also effectively solve the problems of under‐segmentation and over‐segmentation of smoke images.

Carotenoid composition and conformation in retinal oil droplets of the domestic chicken.

Carotenoid-containing oil droplets in the avian retina act as cut-off filters to enhance colour discrimination. We report a confocal resonance Raman investigation of the oil droplets of the domestic chicken, Gallus gallus domesticus. We show that all carotenoids present are in a constrained conformation, implying a locus in specific lipid binding sites. In addition, we provide proof of a recent conclusion that all carotenoid-containing droplets contain a mixture of all carotenoids present, rather than only a subset of them—a conclusion that diverges from the previously-held view. Our results have implications for the mechanism(s) giving rise to these carotenoid mixtures in the differently-coloured droplets.

Wage Discrimination: Blacks VS Whites

Nowadays, we know that discrimination still exists, gender discrimination or skin color discrimination for example. This project is the result of a search on wage discrimination about the skin color. So, the question is: is it true that the black people gain less than the whites? I examine empirically if really exists this type of discrimination through an OLS regression of a set of data from the National Longitudinal Survey (NLS). I found that this discrimination exists and is also statistically significant.

Sex differences in color discrimination and serial reversal learning in mollies and guppies.

Behavioral flexibility provides an individual with the ability to adapt its behavior in response to environmental changes. Studies on mammals, birds, and teleosts indicate greater behavioral flexibility in females. Conversely, males appear to exhibit greater behavioral persistence. We, therefore, investigated sex differences in behavioral flexibility in 2 closely related molly species (Poecilia latipinna, P. mexicana) and their more distant relative, the guppy P. reticulata by comparing male and female individuals in a serial, visual reversal learning task. Fish were first trained in color discrimination, which was quickly learned by all females (guppies and mollies) and all molly males alike. Despite continued training over more than 72 sessions, male guppies did not learn the general test procedure and were, therefore, excluded from further testing. Once the reward contingency was reversed serially, molly males of both species performed considerably better by inhibiting their previous response and reached the learning criterion significantly faster than their respective conspecific females. Moreover, Atlantic molly males clearly outperformed all other individuals (males and females) and some of them even reached the level of 1-trial learning. Thus, the apparently universal pattern of higher female behavioral flexibility seems to be inverted in the 2 examined molly species, although the evolutionary account of this pattern remains highly speculative. These findings were complemented by the observed lower neophobia of female sailfin mollies compared with their male conspecifics. This sex difference was not observed in Atlantic mollies that were observed to be significantly less distressed in a novel situation than their consexuals. Hypothetically, sex differences in behavioral flexibility can possibly be explained in terms of the different roles that males and females play in mating competition, mate choice, and reproduction or, more generally, in complex social interactions. Each of these characteristics clearly differed between the closely related mollies and the more distantly related guppies.

Barriers block the effect of joint attention on working memory: Perspective taking matters.

Joint focus of attention between two individuals can influence the way that observers attend, encode, and value items. Using a nonpredictive gaze cuing task we previously found that working memory (WM) was better for jointly attended (validly cued) versus invalidly cued colored squares. Here we examine whether this influence of gaze on WM is driven by observers sharing the perspective of the face cue (mental state account), or simply by increased attention to the cued location (social attention account). To manipulate perspective taking, a closed barrier obstructed the cue face's view of the memoranda, while an open barrier allowed the cue face to "see" the colors. A central cue face flanked by two identical barriers looked left or right, followed 500 ms later by colored squares for encoding which appeared equally often in the validly and invalidly cued locations. After a blank 1,000 ms maintenance interval, participants stated whether a probe color was present or not in the preceding display. When the barrier was open, WM was significantly impaired for invalidly versus validly cued items. When the barrier was closed, the effect of gaze cues on WM was abolished. In contrast, further experiments showed a significant cuing effect on the speed of simple target localization and color discrimination regardless of barrier type. These findings support the mental state account of joint attention in WM, whereby the attentional focus of another alters WM via higher level engagement with the second person perspective. A goal-specific model of perspective taking is proposed. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Impaired Color Discrimination-A Specific Marker of Hallucinations in Lewy Body Disorders.

There is emerging evidence indicating that color discrimination impairments can predict the development of Lewy body dementia in patients with rapid eye movement sleep behavior disorder, Parkinson disease, and in patients with mild cognitive impairment. Despite this clear relationship, color vision deficits are not seen uniformly in patients with dementia with Lewy bodies (DLB), suggesting a more nuanced association with the underlying neuropathology. Visual hallucinations represent a discriminating feature of DLB, and recent evidence implicates visual pathway dysfunction as a significant contributor to this phenomenon. In this study, we examined the relationship between color vision impairment and visual hallucinations, along with other clinical and neuropsychological features in 24 well-characterized patients with DLB alongside 25 healthy controls. Color discrimination impairment was seen in 16 (67%) of 24 DLB participants with a higher error score relative to controls (P = .001). We demonstrate for the first time a strong association between color discrimination errors on the Farnsworth-Munsell 100 hue test and both the presence and severity of hallucinatory symptoms in DLB based on clinician-derived (P = .008) and questionnaire-derived (P = .03) measures. Correlation with clinical and neuropsychological variables revealed that color discrimination is significantly related to visuospatial difficulties measured by the clock-drawing task (P = .02) but not to global measures of cognition, motor severity, age, or disease duration in our cohort. Factor analysis confirmed a unique relationship between color discrimination, visual hallucinations, and visuospatial function. Our results suggest that color discrimination does not simply relate to dementia but rather indexes higher order perceptual deficits that may predict visual hallucinations in Lewy body disorders and share a common pathophysiological substrate.

Success of the receptor noise model in predicting colour discrimination in guppies depends upon the colours tested

Accurate knowledge of species colour discrimination is fundamental to explain colour based behaviours and the evolution of colour patterns. We tested how the receptor noise limited model, widely used in behavioural ecology, matched actual colour discrimination thresholds obtained using behavioural tests. Guppies (Poecilia reticulata) were first trained to push a target coloured disk placed among eight grey disks of various luminances on a grey plate. Guppies were then tested to find target disks, which varied in colour contrast from the plate. The target disks followed a gradient going from high contrast to inconspicuous against the grey background. We plotted the percentage of correct choices of each colour in the gradient against the model prediction and determined the discrimination thresholds using the inflection point of the fitted sigmoid curve. We performed the experiment on six colour gradients: red, orange, yellow, green, blue and purple. Four colour gradients: red, orange, green and blue, showed a discrimination threshold that matched the model predictions. However, deviations of the model for the yellow and purple gradients suggest that ecological relevance of some colours could affect decision-making in behavioural tests and that we can no longer assume that the rules for colour discrimination are independent of colours.

Floral colour structure in two Australian herbaceous communities: it depends on who is looking.

Pollinator-mediated interactions between plant species may affect the composition of angiosperm communities. Floral colour signals should play a role in these interactions, but the role will arise from the visual perceptions and behavioural responses of multiple pollinators. Recent advances in the visual sciences can be used to inform our understanding of these perceptions and responses. We outline the application of appropriate visual principles to the analysis of the annual cycle of floral colour structure in two Australian herbaceous communities. We used spectrographic measurements of petal reflectance to determine the location of flowers in a model of hymenopteran colour vision. These representations of colour perception were then translated to a behaviourally relevant metric of colour differences using empirically calibrated colour discrimination functions for four hymenopteran species. We then analysed the pattern of colour similarity in terms of this metric in samples of co-flowering plants over the course of a year. We used the same method to analyse the annual pattern of phylogenetic relatedness of co-flowering plants in order to compare colour structure and phylogenetic structure. Co-flowering communities at any given date seldom had colour assemblages significantly different from random. Non-random structure, both dispersion and clustering, occurred occasionally, but depended on which bee observer is considered. The degree of colour similarity was unrelated to phylogenetic similarity within a co-flowering community. Perceived floral colour structure varied with the sensory capabilities of the observer. The lack of colour structure at most sample dates, particularly the rarity of strong dispersion, suggests that plants do not use chromatic signals primarily to enable bees to discriminate between co-flowering species. It is more likely that colours make plants detectable in a complex landscape.

An Adjusted Error Score Calculation for the Farnsworth-Munsell 100 Hue Test

ABSTRACTThe Farnsworth-Munsell 100 Hue Test, a test that measures an individual’s hue discrimination ability, operates with the fundamental assumption that it is administered using a fixed, standard illuminant. This assumption is violated when the testing illuminant is changed—as is common when testing color discrimination ability of an illuminant—which likely causes a reordering of the caps in the test. To ensure that a participant is not falsely penalized for correctly responding to a hue transposition caused by the new testing light source, an adjusted error score is proposed that reconciles light source–induced hue transpositions and participant performance on the test.

The Cambridge Colour Test: Reliability of discrimination trivectors in colour space

Background: The reliable assessment of colour discrimination has become increasingly important as some ophthalmic diseases and systemic conditions manifest themselves via acquired impairments of colour vision. The Cambridge Colour Test (CCT) is a computerised procedure, developed using the basic principles of traditional pseudoisochromatic plates to evaluate colour function or discrimination. Aim: The study investigated reliability of the CCT, with emphasis on the Trivector subtest, which measures thresholds along the three protan, deutan and tritan confusion lines to probe the sensitivity of the long, medium and short wavelength cones. Setting: The study used a prospective observational and quantitative design and took place in a research and clinical environment within the Department of Optometry at the University of Johannesburg, South Africa. Participants were 20 young adults of both genders aged 19–24 years with normal colour vision. Methods: Two measurements (test and retest) of the Trivector test were measured monocularly (right eye) for all participants to assess the reliability of repeated measurements. Reliability was assessed using coefficients of repeatability, coefficients of variation and Bland–Altman plots with limits of agreement (LoA). Results: Outcomes for the Bland–Altman LoA showed good intra-individual agreement and coefficients of repeatability and reliability revealed generally high test–retest repeatability. Multivariate stereo-pair scatter plot comparisons of means and differences of test and retest measurements show that points cluster tightly within the same region in the three-dimensional colour space, and the centroids of the ellipsoids representing the mean differences are close to the origin at zero. Conclusion: Although departure from normality and outlying values can have important influences, essentially the CCT provides very similar test and retest results for the Trivector test.

Libertatea religioasă în dreptul Uniunii Europene

The EU Charter of Fundamental Rights has become a benchmark&nbsp;which enabled the European Court of Human Rights to expand de facto the&nbsp;scope of the European Convention on Human Rights and to produce therefore&nbsp;major jurisprudential revivals. The freedom of thought, conscience and&nbsp;religion is one of the foundations of a democratic society. In its religious dimension, the freedom represents one of the key elements consolidating the identity of the believers and their outlook on life. By its treaties, legislation adopted and jurisprudence, as well as the protection of relating institutions, the European Union stresses on how important it is to respect the fundamental human rights, the religious and philosophical convictions in the European society and lays emphasis on the fundamental values of pluralism and tolerance. The European Union forbids all and any gender, race, colour, ethnic or social origin discrimination, as well as discrimination relating to genetic characteristics, language, religion or convictions, political opinions or opinions of any other nature, affiliation to a national minority, wealth, birth, disabilities, age or sexual orientation-related discrimination. The right to religious freedom is mainly a right pertaining to individual conscience which&nbsp;also involves the freedom to manifest a religion, a religious or philosophical conviction, one’s own perspective on life. The European Union respects cultural, religious and linguistic diversity and does not prejudice the status from which churches and religious associations or communities in the members states benefit under national law.

Psychophysics of the hoverfly: categorical or continuous color discrimination?

There is increasing interest in flies as potentially important pollinators. Flies are known to have a complex visual system, including 4 spectral classes of photoreceptors that contribute to the perception of color. Our current understanding of how color signals are perceived by flies is based on data for the blowfly Lucilia sp., which after being conditioned to rewarded monochromatic light stimuli, showed evidence of a categorical color visual system. The resulting opponent fly color space has 4 distinct categories, and has been used to interpret how some fly pollinators may perceive flower colors. However, formal proof that flower flies (Syrphidae) only use a simple, categorical color process remains outstanding. In free-flying experiments, we tested the hoverfly Eristalis tenax, a Batesian mimic of the honeybee, that receives its nutrition by visiting flowers. Using a range of broadband similar–dissimilar color stimuli previously used to test color perception in pollinating hymenopteran species, we evaluated if there are steep changes in behavioral choices with continuously increasing color differences as might be expected by categorical color processing. Our data revealed that color choices by the hoverfly are mediated by a continuous monotonic function. Thus, these flies did not use a categorical processing, but showed evidence of a color discrimination function similar to that observed in several bee species. We therefore empirically provide data for the minimum color distance that can be discriminated by hoverflies in fly color space, enabling an improved understanding of plant–pollinator interactions with a non-model insect species.

Language and Color Perception: Evidence From Mongolian and Chinese Speakers.

The present research contributes to the debate in cognitive sentence on the relationship between language and perception by comparing Mongolian and Chinese speakers’ color perception. In this study, featuring a free sorting task and a visual search task comparing Mongolian and Chinese performances, the results show that both universal and relativistic forces are at play. Chinese (Mandarin) and Mongolian color terms divide the blue spectrum differently but the green spectrum, similarly. In Mongolian, light blue (“qinker”) and dark blue (“huhe”) are strictly distinct, while both light green and dark green are described as one word, nogvgan. In Chinese, however, both light blue and dark blue are simply described by one word, lan, and both light green and dark green are described by a single word, lv. The current study used a free-sorting task and a visual search task to investigate whether this linguistic difference between Chinese and Mongolian speakers leads to a difference in color discrimination. In the free-sorting task, compared with Chinese speakers, Mongolian speakers exhibited different sorting in the blue region (by distinguishing light and dark blue) and the same sorting in the green region. Further results showed that Mongolian speakers discriminated visual search displays that fall into different linguistic categories in Mongolian (e.g., qinker or huhe) more quickly than visual search displays that belong to the same linguistic category (e.g., both qinker) in a visual search task. Moreover, this effect was disrupted in Mongolian participants who performed a secondary task engaging involving verbal working memory (but not a task engaging involving spatial working memory), suggested linguistic interference. Chinese (Mandarin) speakers performing the visual search task did not show such a category advantage under any of the conditions. The finding provides support for the Whorf hypothesis with evidence from an Altay language. Meanwhile, both Chinese and Mongolian speakers reacted faster to the green color than the blue color in the visual search task, suggesting that the variation in human color perception is constrained by certain universal forces. The difference in categorical effects between Chinese and Mongolian speakers in the blue region suggests a relativistic aspect of language and color perception, while the speed of visual search in blue and green suggests a universalistic aspect of language and color perception. Thus, our findings suggest that our perception is shaped by both relativistic and universal forces.

Hue rotation (HR) and hue blending (HB): Real‐time image enhancement methods for digital component video signals to support red‐green color‐defective observers

AbstractThe mutual understanding of color‐normal observers (CNOs) and color‐defective observers (CDOs) is now essential because personal color information display environments have been widely adopted. However, existing tools for CDOs offer only color discrimination; they fail to support color impression (ie, saturation and contrast). Therefore, we need a novel tool that offers help in distinguishing opponent colors, while preserving color saturation. We introduce two key techniques for realizing this difficult goal. The former is the repeated sequential display of the original and processed images to support the formation of unified correct percepts that provide discrimination of both red‐green and yellow‐blue opponent colors. One image, ie, original, exhibits correct yellow‐blue but distorted red‐green information for CDOs while the other, ie, processed, provides synthesized distinguishable red‐green but confusable yellow‐blue information for CDOs; here, hue rotation (HR) is useful for advanced users whereas hue blending (HB) is suitable for general. The latter is realized by the real‐time video processing available on smartphones; our algorithms support direct processing of the digital component video signal formats (eg, Y, CR, and CB). Subjective tests suggest that the two above‐mentioned algorithms will, along with embedding a lightweight real‐time dichromatic simulation facility for CNOs, greatly help the mutual understanding of CNOs and CDOs.

Electrodiagnosis of dichromacy

Retinal and cortical signals initiated by a single cone type can be recorded using the spectral compensation (or silent substitution) paradigm. Moreover, responses to instantaneous excitation increments combined with gradual excitation decreases are dominated by the response to the excitation increment. Similarly, the response to a sudden excitation decrement dominates the overall response when combined with a gradual excitation increase. Here ERGs and VEPs were recorded from 34 volunteers [25.9 ± 10.4 years old (mean ± 1 SD); 25 males, 9 females] to sawtooth flicker (4 Hz) stimuli that elicited L- or M-cone responses using triple silent substitution. The mean luminance (284 cd/m2) and the mean chromaticity (x = 0.5686, y = 0.3716; CIE 1931 color space) remained constant and thus the state of adaptation was the same in all conditions. Color discrimination thresholds along protan, deutan, and tritan axes were obtained from all participants. Dichromatic subjects were genetically characterized by molecular analysis of their opsin genes. ERG responses to L-cone stimuli were absent in protanopes whereas ERG responses to M-cone stimuli were strongly reduced in deuteranopes. Dichromats showed generally reduced VEP amplitudes. Responses to cone-specific stimuli obtained with standard electrophysiological methods may give the same classification as that obtained with the Cambridge Colour Test and in some cases with the genetic analysis of the L- and M-opsin genes. Therefore, cone-specific ERGs and VEPs may be reliable methods to detect cone dysfunction. The present data confirm and emphasize the potential use of cone-specific stimulation, combined with standard visual electrodiagnostic protocols.

Psychophysical Evaluation of Visual Functions of Ex-Alcoholic Subjects After Prolonged Abstinence.

Chronic alcohol abuse can lead to a brain damages, and the health status of alcoholics even after a long-term alcohol abstinence is a public health concern. The present study investigated the color vision and spatial luminance contrast sensitivity of a group of 17 ex-alcoholics (46.3 ± 6.7 years old) in long-term alcohol abstinence after having been previously under alcohol dependence for many years. We also investigated the association of impaired psychophysical performance in different tests we applied. The mean time of alcohol consumption was 16.9 ± 5.1 years and the mean abstinence period was 12.4 ± 8.5 years. Achromatic vision of all subjects was evaluated using spatial luminance contrast sensitivity function (CSF) test and color vision was evaluated using Mollon–Reffin color discrimination test (MR) and the Farnsworth–Munsell 100 hue arrangement test (FM100). Relative to controls, the spatial luminance contrast sensitivity was lower in 10/17 of the ex-alcoholic subjects. In the color vision tests, 11/16 ex-alcoholic subjects had impaired results compared to controls in the FM100 test and 13/14 subjects had color vision deficits measured in the MR test. Fourteen subjects performed all visual tests, three subjects had impaired results for all tests, seven subjects had impaired results in two tests, three subjects had visual deficit in one test, and one had normal results for all tests. The results showed the existence of functional deficits in achromatic and chromatic vision of subjects with history of chronic alcoholism after long abstinence. Most subjects had altered result in more than one test, especially in the color vision tests. The present investigation suggests that the damage in visual functions produced by abusive alcohol consumption is not reversed after long term alcohol abstinence.

Color vision in sika deer (Cervus nippon): color discrimination between the three primary colors (red, green, and blue) under light and dark conditions

Color vision in sika deer (Cervus nippon): color discrimination between the three primary colors (red, green, and blue) under light and dark conditions

The colors of natural scenes benefit dichromats

Dichromacy impairs color vision and impoverishes the discrimination of surface colors in natural scenes. Computational estimates based on hyperspectral imaging data from natural scenes suggest that dichromats can discriminate only about 10% of the colors discriminated by normal trichromats. These estimates, however, assume that the colors are equally frequent. Yet, pairs of colors confused by dichromats may be rare and thus have small impact on overall perceived chromatic diversity. This study estimated, empirically, how much dichromats are disadvantaged in discriminating surface colors drawn from natural scenes. The stimulus for the experiment was a scene made of real three-dimensional objects painted with matte white paint and illuminated by a spectrally tunable light source. In each trial the observers saw the scene illuminated by two spectra in two successive time intervals and had to indicate whether the colors perceived in the objects in the two intervals were the same or different. The spectra were drawn randomly from hyperspectral data of natural scenes and therefore represented natural spectral statistics. Four normal trichromats and four dichromats carried out the experiment. It was found that the number of pairs that could be discriminated by dichromats was almost 70% of those discriminated by normal trichromats, a proportion much higher than anticipated from estimates of discernible colors. Moreover, data from model simulations show that normal trichromats and dichromats use lightness differences for discrimination in about 40% and 50% of the discriminable pairs, respectively. Together these results suggest that the color distributions of natural scenes benefit the color vision of dichromats.