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Current Neurology and Neuroscience... Oct 2021Color provides important information about the identity of the objects we encounter. After early processing stages in the retinal cones, thalamus, and occipital cortex,... (Review)
Review
PURPOSE OF REVIEW
Color provides important information about the identity of the objects we encounter. After early processing stages in the retinal cones, thalamus, and occipital cortex, retinal signals reach the ventral temporal cortex for high-level color and object processing, which links color perception with top-down expectations and knowledge. In the language-dominant hemisphere, some of these regions communicate with the language systems; by assigning verbal labels to percepts, these circuits speed up stimulus categorization, and permit fast and accurate inter-individual communication. This paper provides a review of color processing deficits, from dysfunction of wavelength discrimination in the retinal photoreceptors to deficits of high-level processing in the ventral temporal cortex.
RECENT FINDINGS
Neuroimaging evidence defined the existence and localization of color-preferring domains in the ventral occipito-temporal cortex. Evidence from the performance of a brain-damaged patient with color anomia but preserved color categorization demonstrated the independence of color categorization from color naming in the adult brain. Evidence from patients with brain damage suggests that high-level color processing may be divided into at least three functional domains: perceptual color experience, color naming, and color knowledge.
Topics: Anomia; Color Perception; Color Vision; Humans; Magnetic Resonance Imaging; Occipital Lobe
PubMed: 34606018
DOI: 10.1007/s11910-021-01137-8 -
Philosophical Transactions of the Royal... Oct 2022Colour constancy is the ability to recognize the colour of objects despite spectral changes in the natural illumination. As such, this phenomenon is important for most... (Review)
Review
Colour constancy is the ability to recognize the colour of objects despite spectral changes in the natural illumination. As such, this phenomenon is important for most organisms with good colour vision, and it has been intensively studied in humans and primates. Colour constancy is also documented for several species of insects, which is not surprising given the ecological importance of colour vision. But how do insects, with their small brains, solve the complex problem of colour vision and colour constancy? In an interspecies approach, this review reports on behavioural studies on colour constancy in bees, butterflies, moths and humans, corresponding computational models and possible neurophysiological correlates. This article is part of the theme issue 'Understanding colour vision: molecular, physiological, neuronal and behavioural studies in arthropods'.
Topics: Animals; Bees; Butterflies; Color; Color Perception; Color Vision; Humans; Insecta
PubMed: 36058239
DOI: 10.1098/rstb.2021.0286 -
Current Opinion in Insect Science Oct 2016Dragonflies including damselflies are colorful and large-eyed insects, which show remarkable sexual dimorphism, color transition, and color polymorphism. Recent... (Review)
Review
Dragonflies including damselflies are colorful and large-eyed insects, which show remarkable sexual dimorphism, color transition, and color polymorphism. Recent comprehensive visual transcriptomics has unveiled an extraordinary diversity of opsin genes within the lineage of dragonflies. These opsin genes are differentially expressed between aquatic larvae and terrestrial adults, as well as between dorsal and ventral regions of adult compound eyes. Recent topics of color formation in dragonflies are also outlined. Non-iridescent blue color is caused by coherent light scattering from the quasiordered nanostructures, whereas iridescent color is produced by multilayer structures. Wrinkles or wax crystals sometimes enhances multilayer structural colors. Sex-specific and stage-specific color differences in red dragonflies is attributed to redox states of ommochrome pigments.
Topics: Animals; Color Vision; Female; Genes, Insect; Life Cycle Stages; Male; Odonata; Opsins; Sex Factors
PubMed: 27720071
DOI: 10.1016/j.cois.2016.05.014 -
Vision Research Oct 2018
Topics: Color Vision; Humans; Psychophysics; Retinal Cone Photoreceptor Cells
PubMed: 30327094
DOI: 10.1016/j.visres.2018.09.001 -
Vision Research May 2019Retinal and cortical signals initiated by a single cone type can be recorded using the spectral compensation (or silent substitution) paradigm. Moreover, responses to...
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/m) 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.
Topics: Adolescent; Adult; Color Perception Tests; Color Vision; Color Vision Defects; Cone Opsins; Electroretinography; Evoked Potentials, Visual; Female; Humans; Male; Young Adult
PubMed: 30844384
DOI: 10.1016/j.visres.2019.02.011 -
Philosophical Transactions of the Royal... Oct 2022Ants are ecologically one of the most important groups of insects and exhibit impressive capabilities for visual learning and orientation. Studies on numerous ant... (Review)
Review
Ants are ecologically one of the most important groups of insects and exhibit impressive capabilities for visual learning and orientation. Studies on numerous ant species demonstrate that ants can learn to discriminate between different colours irrespective of light intensity and modify their behaviour accordingly. However, the findings across species are variable and inconsistent, suggesting that our understanding of colour vision in ants and what roles ecological and phylogenetic factors play is at an early stage. This review provides a brief synopsis of the critical findings of the past century of research by compiling studies that address molecular, physiological and behavioural aspects of ant colour vision. With this, we aim to improve our understanding of colour vision and to gain deeper insights into the mysterious and colourful world of ants. This article is part of the theme issue 'Understanding colour vision: molecular, physiological, neuronal and behavioural studies in arthropods'.
Topics: Animals; Ants; Color Vision; Insecta; Learning; Phylogeny
PubMed: 36058251
DOI: 10.1098/rstb.2021.0291 -
Indian Journal of Ophthalmology May 2021Color vision deficiency (CVD) is a condition that results in individuals being unable to distinguish differences between certain colors. Occupational color vision... (Review)
Review
Color vision deficiency (CVD) is a condition that results in individuals being unable to distinguish differences between certain colors. Occupational color vision standards were introduced in aviation in 1919 by The Aeronautical Commission of the International Civil Air Navigation Authority. Concern has been expressed during the last few years that the current color vision standards in aviation may be too stringent and, at the same time, also variable across the world. The tests employed do not always reflect the tasks pilots encounter in today's aviation environment. This ambiguity leads to the possible exclusion of deserving applicants for selection as aircrew. The compatibility of CVD with aircraft crew is assessed by medical personnel using clinical diagnosis tests on the ground level. These clinical tests were developed specifically to detect the presence, nature, and severity of CVD. No clinical tests yet provide a measure of operational performance in operating an aircraft. Arbitrary pass marks have been assigned to clinical tests such that a failing candidate will either be subject to operational restrictions or excluded completely. The prescribed clinical tests and associated pass marks vary considerably between regulators. While an individual may be subject to no restrictions in one jurisdiction, they may be excluded in another. This article highlights newer diagnostic techniques adopted by different countries for assessing color vision to see for the scope of evidence-based guidelines for minimum color vision requirements for flight crew as well as for civil aviation in India.
Topics: Aviation; Color Perception Tests; Color Vision; Color Vision Defects; Humans; India
PubMed: 33913828
DOI: 10.4103/ijo.IJO_2252_20 -
Philosophical Transactions of the Royal... Oct 2022The ability to see colour at night is known only from a handful of animals. First discovered in the elephant hawk moth , nocturnal colour vision is now known from two... (Review)
Review
The ability to see colour at night is known only from a handful of animals. First discovered in the elephant hawk moth , nocturnal colour vision is now known from two other species of hawk moths, a single species of carpenter bee, a nocturnal gecko and two species of anurans. The reason for this rarity-particularly in vertebrates-is the immense challenge of achieving a sufficient visual signal-to-noise ratio to support colour discrimination in dim light. Although no less challenging for nocturnal insects, unique optical and neural adaptations permit reliable colour vision and colour constancy even in starlight. Using the well-studied , we describe the visual light environment at night, the visual challenges that this environment imposes and the adaptations that have evolved to overcome them. We also explain the advantages of colour vision for nocturnal insects and its usefulness in discriminating night-opening flowers. Colour vision is probably widespread in nocturnal insects, particularly pollinators, where it is likely crucial for nocturnal pollination. This relatively poorly understood but vital ecosystem service is threatened from increasingly abundant and spectrally abnormal sources of anthropogenic light pollution, which can disrupt colour vision and thus the discrimination and pollination of flowers. This article is part of the theme issue 'Understanding colour vision: molecular, physiological, neuronal and behavioural studies in arthropods'.
Topics: Animals; Bees; Color Perception; Color Vision; Ecosystem; Flowers; Insecta; Lizards; Pollination
PubMed: 36058247
DOI: 10.1098/rstb.2021.0285 -
Current Biology : CB Feb 2021A new study has used magnetoencephalography to track cortical responses to color as they emerge in time. Similarities and differences within these neural responses...
A new study has used magnetoencephalography to track cortical responses to color as they emerge in time. Similarities and differences within these neural responses parallel characteristics of the perceptual experience of color.
Topics: Color Perception; Color Vision; Humans; Magnetoencephalography
PubMed: 33561408
DOI: 10.1016/j.cub.2020.11.056 -
The Journal of Physiology Sep 1953
Topics: Color Perception; Color Vision; Color Vision Defects; Humans
PubMed: 13097391
DOI: 10.1113/jphysiol.1953.sp004964