Color Discrimination Research Articles

Wild hummingbirds discriminate nonspectral colors.

Many animals have the potential to discriminate nonspectral colors. For humans, purple is the clearest example of a nonspectral color. It is perceived when two color cone types in the retina (blue and red) with nonadjacent spectral sensitivity curves are predominantly stimulated. Purple is considered nonspectral because no monochromatic light (such as from a rainbow) can evoke this simultaneous stimulation. Except in primates and bees, few behavioral experiments have directly examined nonspectral color discrimination, and little is known about nonspectral color perception in animals with more than three types of color photoreceptors. Birds have four color cone types (compared to three in humans) and might perceive additional nonspectral colors such as UV+red and UV+green. Can birds discriminate nonspectral colors, and are these colors behaviorally and ecologically relevant? Here, using comprehensive behavioral experiments, we show that wild hummingbirds can discriminate a variety of nonspectral colors. We also show that hummingbirds, relative to humans, likely perceive a greater proportion of natural colors as nonspectral. Our analysis of plumage and plant spectra reveals many colors that would be perceived as nonspectral by birds but not by humans: Birds' extra cone type allows them not just to see UV light but also to discriminate additional nonspectral colors. Our results support the idea that birds can distinguish colors throughout tetrachromatic color space and indicate that nonspectral color perception is vital for signaling and foraging. Since tetrachromacy appears to have evolved early in vertebrates, this capacity for rich nonspectral color perception is likely widespread.

Categorical face perception in fish: How a fish brain warps reality to dissociate "same" from "different".

Categorical perception (CP) is the phenomenon by which a smoothly varying stimulus property undergoes a nonlinear transformation during processing in the brain. Consequently, the stimuli are perceived as belonging to distinct categories separated by a sharp boundary. Originally thought to be largely innate, the discovery of CP in tasks such as novel image discrimination has piqued the interest of cognitive scientists because it provides compelling evidence that learning can shape a category's perceptual boundaries. CP has been particularly closely studied in human face perception. In nonprimates, there is evidence for CP for sound and color discrimination, but not for image or face discrimination. Here, we investigate the potential for learned CP in a lower vertebrate, the damselfish Pomacentrus amboinensis. Specifically, we tested whether the ability of these fish to discriminate complex facial patterns tracked categorical rather than metric differences in the stimuli. We first trained the fish to discriminate sets of two facial patterns. Next, we morphed between these patterns and determined the just noticeable difference (JND) between a morph and original image. Finally, we tested for CP by analyzing the discrimination ability of the fish for pairs of JND stimuli along the spectrum of morphs between two original images. Discrimination performance was significant for the image pair straddling the boundary between categories, and chance for equivalent stimulus pairs on either side, thus producing the classic "category boundary" effect. Our results reveal how perception can be influenced in a top-down manner even in the absence of a visual cortex.

Prospective deep phenotyping of choroideremia patients using multimodal structure-function approaches

ObjectiveTo investigate the retinal changes in choroideremia (CHM) patients to determine correlations between age, structure and function.Subjects/MethodsTwenty-six eyes from 13 male CHM patients were included in this prospective longitudinal study. Participants were divided into <50-year (n = 8) and ≥50-year (n = 5) old groups. Patients were seen at baseline, 6-month, and 1-year visits. Optical coherence tomography (OCT), OCT angiography, and fundus autofluorescence were performed to measure central foveal (CFT) and subfoveal choroidal thickness (SCT), as well as areas of preserved choriocapillaris (CC), ellipsoid zone (EZ), and autofluorescence (PAF). Patients also underwent functional investigations including visual acuity (VA), contrast sensitivity (CS), colour testing, microperimetry, dark adaptometry, and handheld electroretinogram (ERG). Vision-related quality-of-life was assessed by using the NEI-VFQ-25 questionnaire.ResultsOver the 1-year follow-up period, progressive loss was detected in SCT, EZ, CC, PAF, and CFT. Those ≥50-years exhibited more structural and functional defects with SCT, EZ, CC, and PAF showing strong correlation with patient age (rho ≤ −0.47, p ≤ 0.02). CS and VA did not change over the year, but CS was significantly correlated with age (rho = −0.63, p = 0.001). Delayed to unmeasurable dark adaptation, decreased colour discrimination and no detectable ERG activity were observed in all patients. Minimal functional deterioration was observed over one year with a general trend of slower progression in the ≥50-years group.ConclusionsQuantitative structural parameters including SCT, CC, EZ, and PAF are most useful for disease monitoring in CHM. Extended follow-up studies are required to determine longitudinal functional changes.

New techniques for quantification of color vision in disorders of cone function : Cambridge color test and photoreceptor-specific temporal contrast sensitivity in patients with heterozygous RP1L1 and RPGR mutations

HintergrundErbliche Netzhauterkrankungen mit Zapfendysfunktion können trotz relativ unauffälligem Fundusbefund ausgeprägte Visusminderung und deutliche Farbsinnstörungen aufweisen. Beispiele hierfür sind die autosomal-dominante okkulte Makuladystrophie (RP1L1-Gen) und die X‑chromosomale Retinitis pigmentosa (RPGR-Gen) – Letztere auch bei heterozygoten, weiblichen Merkmalsträgerinnen (Konduktorinnen). Neue Untersuchungsmethoden erlauben es, das Ausmaß der Farbsinnstörung zu quantifizieren.MethodenNach einer umfangreichen klinischen Untersuchung führten wir Messungen zur Quantifizierung der Farbdiskriminierung und der Zapfenfunktion durch. Beim Cambridge-Color-Test werden pseudoisochromatische Tafeln mit Landolt-C-Figuren computergesteuert generiert, um die Farbunterscheidungsschwelle entlang mehrerer Achsen im Farbraum zu bestimmen. Bei der Untersuchung der photorezeptorspezifischen zeitlichen Kontrastempfindlichkeit kann durch geschickte zyklische Veränderung der spektralen Zusammensetzung eines Lichtreizes die Kontrastwahrnehmungsschwelle isolierter Photorezeptortypen bestimmt werden. Die molekulargenetische Diagnostik erfolgte mithilfe von Next Generation Sequencing(NGS)-basierter gezielter Genpanelanalyse sowie Sanger-Sequenzierung.ErgebnisseBei 2 Patienten mit okkulter Makuladystrophie und 2 heterozygoten Trägerinnen von RPGR-Mutationen zeigten sich eine deutlich verminderte Fähigkeit zur Farbdiskriminierung und eine verminderte photorezeptorspezifische zeitliche Kontrastempfindlichkeit.DiskussionBei erblichen Netzhauterkrankungen sind neben den modernen bildgebenden Verfahren (okuläre Kohärenztomographie [OCT] und Fundusautofluoreszenz) auch die sinnesphysiologischen Untersuchungen diagnostisch wegweisend – der Nachweis von Farbsinnstörungen spielt hierbei eine wichtige Rolle. Neuere Methoden erlauben eine Quantifizierung der Farbsinnstörungen und könnten in klinischen Studien zu gen- und stammzellbasierter Therapie zur Messung des Therapieerfolges dienen.

Color ensembles: Sampling and averaging spatial hue distributions

Color serves both to segment a scene into objects and background and to identify objects. Although objects and surfaces usually contain multiple colors, humans can readily extract a representative color description, for instance, that tomatoes are red and bananas yellow. The study of color discrimination and identification has a long history, yet we know little about the formation of summary representations of multicolored stimuli. Here, we characterize the human ability to integrate hue information over space for simple color stimuli varying in the amount of information, stimulus size, and spatial configuration of stimulus elements. We show that humans are efficient at integrating hue information over space beyond what has been shown before for color stimuli. Integration depends only on the amount of information in the display and not on spatial factors such as element size or spatial configuration in the range measured. Finally, we find that observers spontaneously prefer a simple averaging strategy even with skewed color distributions. These results shed light on how human observers form summary representations of color and make a link between the perception of polychromatic surfaces and the broader literature of ensemble perception.

Application of Fourier Transform Near-Infrared (FT-NIR) and Fourier Transform Infrared (FT-IR) Spectroscopy Coupled with Wavelength Selection for Fast Discrimination of Similar Color of Tuber Flours

This research aimed at providing a fast and accurate method in discriminating tuber flours having similar color by using Fourier transform near-infrared (FT-NIR) and Fourier transform infrared (FT-IR) spectroscopy in order to minimize misclassification if using human eye or avoid adulteration. Reflectance spectra of three types of tubers (consisted of Canna edulis, modified cassava, and white sweet potato) were collected to develop a multivariate model of partial least-squares discriminant analysis (PLS-DA). Several spectra preprocessing methods were applied to obtain the best calibration and prediction model, while variable importance in the projection (VIP) wavelength selection method was used to reduce variables in developing the model. The PLS-DA model achieved 100% accuracy in predicting all types of flours, both for FT-NIR and FT-IR. The model was also able to discriminate all flours with coefficient of determination (R2) of 0.99 and a standard error of prediction (SEP) of 0.03% by using 1st Savitzky Golay (SG) derivative method for the FT-NIR data, as well as R2 of 0.99 and SEP of 0.08% by using 1st Savitzky Golay (SG) derivative method for the FT-IR data. By applying the VIP method, the variables were reduced from 1738 to 608 variables with R2 of 0.99 and SEP of 0.09% for FT IR and from 1557 to 385 variables with R2 of 0.99 and SEP of 0.05% for FT NIR.

Development of a new optical-based quasi-digital particle discrimination technique using inorganic scintillators

In this study, we propose an original approach for particle discrimination in a mixed radiation field using scintillators. The method relies on the possibility to identify the point of interaction in a phoswich detector from the emission spectra of the produced scintillation light, using optical filters as passive selectors. As a proof of concept, we developed a compact prototype thermal neutron active dosimeter for mixed neutron/gamma fields. The detector was characterized in terms of energy calibration, neutron efficiency and gamma rejection. The obtained results show that more than the 99% of counts due to gamma rays are rejected if the color discrimination is employed, thus demonstrating the feasibility of the proposed approach to be used in radiation detection.

Clinical and Imaging Markers of Prodromal Parkinson's Disease.

The diagnosis of Parkinson's disease (PD) relies on the clinical effects of dopamine deficiency, including bradykinesia, rigidity and tremor, usually manifesting asymmetrically. Misdiagnosis is common, due to overlap of symptoms with other neurodegenerative disorders such as multiple system atrophy and progressive supranuclear palsy, and only autopsy can definitively confirm the disease. Motor deficits generally appear when 50–60% of dopaminergic neurons in the substantia nigra are already lost, limiting the effectiveness of potential neuroprotective therapies. Today, we consider PD to be not just a movement disorder, but rather a complex syndrome non-motor symptoms (NMS) including disorders of sleep-wake cycle regulation, cognitive impairment, disorders of mood and affect, autonomic dysfunction, sensory symptoms and pain. Symptomatic LRRK2 mutation carriers share non-motor features with individuals with sporadic PD, including hyposmia, constipation, impaired color discrimination, depression, and sleep disturbance. Following the assumption that the pre-symptomatic gene mutation carriers will eventually exhibit clinical symptoms, their neuroimaging results can be extended to the pre-symptomatic stage of PD. The long latent phase of PD, termed prodromal-PD, represents an opportunity for early recognition of incipient PD. Early recognition could allow initiation of possible neuroprotective therapies at a stage when therapies might be most effective. The number of markers with the sufficient level of evidence to be included in the MDS research criteria for prodromal PD have increased during the last 10 years. Here, we review the approach to prodromal PD, with an emphasis on clinical and imaging markers and report results from our neuroimaging study, a retrospective evaluation of a cohort of 39 participants who underwent DAT-SPECT scan as part of their follow up. The study was carried out to see if it was possible to detect subclinical signs in the preclinical (neurodegenerative processes have commenced, but there are no evident symptoms or signs) and prodromal (symptoms and signs are present, but are yet insufficient to define disease) stages of PD.

A randomized clinical trial comparing prompt photodynamic therapy with 3 months observation in patients with acute central serous chorioretinopathy with central macular leakage.

The purpose of the study was to demonstrate whether photodynamic therapy in patients with acute central serous chorioretinopathy, with the leakage point within one optic disk diameter from the fovea, can be safely deferred. A single-center, randomized, controlled trial was conducted. Patients were randomized to photodynamic therapy within a week after presentation (Group I, 26 patients) or observation during 3 months (Group II, 26 patients). If leakage or subretinal fluid was observed during any control visit, photodynamic therapy was performed (again) within a week. Primary outcome was change of visual acuity (Early Treatment Diabetic Retinopathy Study) after 12 months. Secondary outcomes were visual acuity, central foveal thickness, metamorphopsia, and color discrimination. Photodynamic therapy procedures: group I, 26 at baseline, 2 retreatments at 3 months; group II, 10 at 3 months, 1 at 6 months (2 subjects refusing treatment), 2 retreatments at 6 months. At 12 months, mean visual acuity of all patients had improved by 6.5 letters (P < 0.001), mean central foveal thickness was 172 µm less (P < 0.001). After photodynamic therapy, visual acuity recovered faster and metamorphopsia significantly improved (3 months, P < 0.001). Differences between groups at 12 months were not significant. The (intended) number of photodynamic therapy (re)treatments in group II (n = 15) was 46% less than in group I (n = 28). Visual acuity and central foveal thickness at 12 months were similar. Therefore, the preferred management of acute central serous chorioretinopathy at presentation appears to be observation for 3 months.

Russian blues reveal the limits of language influencing colour discrimination

Chromatic stimuli across a boundary of basic colour categories (BCCs; e.g. blue and green) are discriminated faster than colorimetrically equidistant colours within a given category. Russian has two BCCs for blue, sinij ‘dark blue’ and goluboj ‘light blue’. These language-specific BCCs were reported to enable native Russian speakers to discriminate cross-boundary dark and light blues faster than English speakers (Winawer et al., 2007, PNAS, 4, 7780–7785). We re-evaluated this finding in two experiments that employed identical tasks as in the cited study. In Experiment 1, Russian and English speakers categorised colours as sinij/goluboj or dark blue/light blue respectively; this was followed by a colour discrimination task. In Experiment 2, Russian speakers initially performed the discrimination task on sinij/goluboj and goluboj/zelënyj ‘green’ sets. They then categorised these colours in three frequency contexts with each stimulus presented: (i) an equal number of times (unbiased); more frequent (ii) either sinij or goluboj; (iii) either goluboj or zelënyj. We observed a boundary response speed advantage for goluboj/zelënyj but not for sinij/goluboj. The frequency bias affected only the sinij/goluboj boundary such that in a lighter context, the boundary shifted towards lighter shades, and vice versa. Contrary to previous research, our results show that in Russian, stimulus discrimination at the lightness-defined blue BCC boundary is not reflected in processing speed. The sinij/goluboj boundary did have a sharper categorical transition than the dark blue/light blue boundary, but it was also affected by frequency and order biases, demonstrating that “Russian blues” are less well-structured than previously thought.

Critical bottom-up attentional factors in the handle orientation effect: asymmetric luminance transients and object-center eccentricity relative to fixation.

In 1998, Tucker and Ellis found that keypress responses are faster when the task-irrelevant orientation of a graspable object's handle corresponds to response hand location. Over the past 20years, researchers have disagreed over the extent to which grasping affordance or spatial compatibility contributes to the effect. One of the causes behind the conflicting findings and interpretations may be that studies advocating the grasping affordance view have tended to overlook the contributions of low-level perceptual characteristics to the observed correspondence effects. The present study evaluated the role of visual salience and bottom-up attention in the occurrence of the effect. Experiment 1 involved a vertical orientation task (bimanual keypresses) using photographs of graspable objects, centered based on object width or pixel area. The same procedure was performed using a color discrimination task on solid-colored silhouettes, large (Experiment 2) and small-sized (Experiment 3), as well as silhouette outlines (Experiment 4). Similar result patterns across Experiments 1-3 were observed and discussed in the context of diverging findings in Experiment 4, prompting us to introduce the notion of asymmetry-based Simon effects, whereby location is coded at stimulus onset on the basis of asymmetric changes in luminance between both hemifields, coupled with object-center eccentricity relative to fixation. These low-level factors were critical in modulating the temporal dynamics, as well as the direction of compatibility effects (toward handles or bodies), irrespective of grasping affordance, task, object identity, or stimulus size. The present findings provide further evidence that the Tucker and Ellis paradigm for studying variable affordances is extremely vulnerable to location-coding, which may arise on the basis of exogenous deployments of attention. This problem is only exacerbated in a large portion of the relevant literature, whereby visually complex stimuli are primarily discussed in terms of their graspable nature and relation to task, rather than their low-level, attention-capturing features.

Modifying twisted nematic LCD screens to create dichromatic visual stimuli with LEDs

Abstract The use of computers to create and display animations/videos in the study of visually guided behaviours has been instrumental in understanding sensory mechanisms underlying complex traits. Using computer displays, scientists are able to create a wide array of colours using three differently coloured lights (Red, Green, Blue [RGB]). While it is possible to generate scenes with RGB displays that mimic animals' colour perceptual experience, this can be problematic because it requires knowledge of the spectral absorbance of the animals' photoreceptor classes, which are often unknown and are difficult to obtain. Even then, stimuli are limited to the central part of the visible spectrum (e.g. ultraviolet (UV) stimuli are not possible). We present a cost‐effective way of modifying a twisted nematic LCD screen that utilizes coloured LEDs, that allows measuring animals' sensitivity to, and discrimination between, wavelengths of light. It has the benefit of not requiring a‐priori knowledge of animals' photoreceptor classes. An LCD screen can be modified by removing the screen's back polarizer (behind the liquid crystal layer) and backlighting the screen with LEDs of two different colours. One of the LED colours transmits through a polarizer with a transmission axis parallel to the screen's front polarizer, and other LED colour transmits through a polarizer orthogonal to the first. To test colour discrimination, one can create a dichromatic stimulus in which both LED colours are ‘ON’ and the current through one LED colour is decreased, while the other is constant, which generated a maximum intensity contrast of 1.84 log units in our setup. To test colour sensitivity, one can create a monochromatic stimulus in which only one LED colour is ‘ON’, which generates a contrast similar to the dichromatic stimulus. This technique overcomes many of the limitations of RGB‐based LCD screens in a cost‐effective way, and allows more accurate testing of the role of colour in visually guided behaviours. Besides the questions in vision research, this setup can answer, it can also be used as an outreach tool in classrooms where children can learn about light, colour, polarization and technology.

Visual acuity and color discrimination in patients with cataracts.

Color vision tests can give information about pathological changes in eye structures. The purpose of our research was to study the color vision sensitivity and visual acuity changes before and after cataract surgery. We used a saturated Farnsworth D15 color vision arrangement test to check color sensitivity changes in confusion line directions. The test is easily perceptible (essential to eldery patients), and it is possible to check color sensitivity changes in tritan, protan, and deutan confusion line directions. The results were analyzed in several ways: by summing the color differences between adjacent caps according to Bowman and averaging the color difference vectors according to Vingrys and King-Smith. Color difference vectors determine the severity (or confusion), selectivity (or scatter), and type of color deficiency to the presented cap arrangements. In the least squares regression method, the error type is determined by the angular proximity of the best-fit line to known confusion axes representing protan, deutan, tritan, or unspecified color defects. All three tests showed that cataract-induced lens opacity significantly decreases a patient's chromatic resolution in the visible light region. Before the cataract surgery, the D15 test stimulus arrangement sequence showed similarities with tritan color deficiency.

Color quality evaluation of Chinese bronzeware in typical museum lighting.

A series of psychophysical experiments have been conducted to investigate the effect of light sources on the color appearance of Chinese bronzeware. Three groups of 30 observers were asked to evaluate a set of Chinese bronzeware under different light sources in three paired-comparison experiments-one group of observers for each experiment. The visual attributes of color preference, color comfort, color discrimination, and antiquity were scaled. A panel of seven light sources of 3000 K, with Duv values ranging from $ - {0}.{015}$-0.015 to 0.015, was used in Experiment 1. A second panel of seven light sources of 4000 K, with a similar range of Duv values, was used in Experiment 2. For Experiment 3, six light sources were chosen from Exps. 1 and 2, plus four lights of 2700 K, 3300 K, 3700 K, and 4300 K, with Duv values of zero. These experimental lights produced a constant illuminance of approximately 200 lux in a pair of viewing booths, and their color rendering indices were between 88 and 95. The results showed that the subjective judgments for color preference and color comfort were highly correlated while the whiteness of the lighting strongly influenced the perception of color preference, comfort, and discrimination. A light source of 4000 K with a Duv value of zero exhibited the best color preference and color comfort performance, while observers were found to show the greatest capability for color discrimination under a light source of 4000 K with a Duv value of $ - {0}.{015}$-0.015. In addition, the bronzeware appeared to have greatest antiquity when illuminated by a 3000 K light source with a Duv value equal to 0.005. Based on the psychophysical data, the performance of typical color quality metrics were also tested in relation to the four scaled visual attributes.

Development of a direct and visual isothermal method for meat adulteration detection in low resource settings

Simple, fast and efficient method for on-site detection of meat adulteration is of increasing demand in low-resource regions. Here, a direct and visual denaturation bubble-mediated strand exchange amplification method (SEA) was developed to detect meat adulteration by targeting the mitochondrial sequence from duck, which required only a heating block. The method allowed detecting as low as 10 pg/μL duck DNA and 0.1% duck meat in binary mixtures, sufficiently meeting the demand of meat adulteration detection. Notably, the method realized instrument-free readout by significant color discrimination of positive and negative results. By coupling with fast DNA release, a direct SEA method was developed and reduced the whole detection time to 1 h, eliminating complex DNA extraction process. The developed method provided a promising strategy with integration of fast sample lysis, miniaturized reaction platform and visual readout for meat adulteration, especially suitable for low resource point-of-care settings.

Action information contributes to metacognitive decision-making

Metacognitive abilities allow us to adjust ongoing behavior and modify future decisions in the absence of external feedback. Although metacognition is critical in many daily life settings, it remains unclear what information is actually being monitored and what kind of information is being used for metacognitive decisions. In the present study, we investigated whether response information connected to perceptual events contribute to metacognitive decision-making. Therefore, we recorded EEG signals during a perceptual color discrimination task while participants were asked to provide an estimate about the quality of their decision on each trial. Critically, the moment participants provided their confidence judgments varied across conditions, thereby changing the amount of action information (e.g., response competition or response fluency) available for metacognitive decisions. Results from three experiments demonstrate that metacognitive performance improved when first-order action information was available at the moment metacognitive decisions about the perceptual task had to be provided. This behavioral effect was accompanied by enhanced functional connectivity (beta phase synchrony) between motor areas and prefrontal regions, exclusively observed during metacognitive decision-making. Our findings demonstrate that action information contributes to metacognitive decision-making, thereby painting a picture of metacognition as a process that integrates sensory evidence and information about our interactions with the world.

How does a threatening stimulus affect the memory of the display?

Ample research has suggested that visual attention is biased towards threat and it was argued that this bias is an essential component of survival and implicated in anxiety. However, it is less clear how this bias is translated into memory, and specifically into the memory of items presented near a threatening stimulus. Here, we investigated this issue by testing how well people remember neutral and threatening images presented under various task demands. On each trial, observers saw two images before performing a dot-probe task (Experiment 1), a colour discrimination task (Experiment 2), a global or local attention task (Experiment 3), or no task at all (Experiment 4). A recognition memory test was performed at the end of each experiment to assess how the presence of a threatening image influences the memory of both images presented in the display. In all experiments, overall memory was enhanced as more threatening images were presented in the display. However, this enhancement did not occur at the expense of the processing of the surroundings. That is, with the exception of the dot-probe task, memory performance was not affected by an adjacent threatening image. Together, these findings challenge trade-off accounts, which predict that the processing of a threatening stimulus should take place at the expense of the processing of nearby items. Instead, these findings suggest that any effect of threat on the visual processing of the display is short-lived and more limited than previously thought.

Color discrimination assessment in patients with hypothyroidism using the Farnsworth-Munsell 100 hue test.

There is evidence in the literature that hypofunction of the thyroid gland (hypothyroidism) affects color vision in rodents by influencing the production of the visual pigment opsin. The effect of hypothyroidism on color vision in humans has not been examined in any great detail. In this cross-sectional study we evaluated color discrimination using the Farnsworth-Munsell 100 hue test (FM-100 test) in 25 individuals with pre-treatment hypothyroidism (mean age ${38}\;{\pm }\;{9}.{2}\;\text{yr}$38±9.2yr), and a control euthyroid group, ${ n} ={26}$n=26 (mean age ${39.6}\;{\pm }\;{8}.{4}\;\text{yr}$39.6±8.4yr). There was no statistically significant difference in the total error score ($\surd{\text{TES}}$√TES) between the groups, but the hypothyroid group had a significantly greater partial error score ($\surd{\text{PES}}$√PES) along the blue-yellow (B-Y) axis compared to the red-green (R-G) axis. No statistically significant differences in B-Y and R-G PES were observed in the control group. This study shows that hypothyroidism affects color vision in humans, causing significant impairment in the B-Y color subsystem.

Visualizing the trade-offs between laser eye protection and laser eye dazzle

Visual detection and color discrimination become more challenging tasks when laser eye protection (LEP) is worn. This is due to the reduced light transmission and wavelength-blocking characteristics of LEP filters. LEP can, however, provide valuable protection against laser eye dazzle—the temporary reduction of vision caused by visible wavelength lasers. To understand this compromise, a model has been developed to allow the visual impacts of LEP to be simulated and balanced against their dazzle protection capabilities. This model is able to use any digital image as a background scene, allowing for real-world visualizations of LEP and dazzle over a broad range of scenarios. The work is built from the CIECAM02 color appearance model and a modified CIE general disability glare equation, together with experimentally validated adjustments to improve the accuracy of this application. The resulting model will help to inform LEP procurement and will serve as an educational tool for LEP users.Visual detection and color discrimination become more challenging tasks when laser eye protection (LEP) is worn. This is due to the reduced light transmission and wavelength-blocking characteristics of LEP filters. LEP can, however, provide valuable protection against laser eye dazzle—the temporary reduction of vision caused by visible wavelength lasers. To understand this compromise, a model has been developed to allow the visual impacts of LEP to be simulated and balanced against their dazzle protection capabilities. This model is able to use any digital image as a background scene, allowing for real-world visualizations of LEP and dazzle over a broad range of scenarios. The work is built from the CIECAM02 color appearance model and a modified CIE general disability glare equation, together with experimentally validated adjustments to improve the accuracy of this application. The resulting model will help to inform LEP procurement and will serve as an educational tool for LEP users.

Late disruption of central visual field disrupts peripheral perception of form and color.

Evidence from neuroimaging and brain stimulation studies suggest that visual information about objects in the periphery is fed back to foveal retinotopic cortex in a separate representation that is essential for peripheral perception. The characteristics of this phenomenon have important theoretical implications for the role fovea-specific feedback might play in perception. In this work, we employed a recently developed behavioral paradigm to explore whether late disruption to central visual space impaired perception of color. In the first experiment, participants performed a shape discrimination task on colored novel objects in the periphery while fixating centrally. Consistent with the results from previous work, a visual distractor presented at fixation ~100ms after presentation of the peripheral stimuli impaired sensitivity to differences in peripheral shapes more than a visual distractor presented at other stimulus onset asynchronies. In a second experiment, participants performed a color discrimination task on the same colored objects. In a third experiment, we further tested for this foveal distractor effect with stimuli restricted to a low-level feature by using homogenous color patches. These two latter experiments resulted in a similar pattern of behavior: a central distractor presented at the critical stimulus onset asynchrony impaired sensitivity to peripheral color differences, but, importantly, the magnitude of the effect was stronger when peripheral objects contained complex shape information. These results show a behavioral effect consistent with disrupting feedback to the fovea, in line with the foveal feedback suggested by previous neuroimaging studies.