scholarly journals A generalized equation for the calculation of receptor noise limited colour distances in n -chromatic visual systems

2017 ◽  
Vol 4 (9) ◽  
pp. 170712 ◽  
Author(s):  
R. C. Clark ◽  
R. D. Santer ◽  
J. S. Brebner
Keyword(s):  
Colour Vision ◽  
Generalized Equation ◽  
Nervous Systems ◽  
Visual Model ◽  
Visual Systems ◽  
Distance Model ◽  
Similarities And Differences ◽  
Single Formula ◽  
Receptor Noise ◽  
Colour Distance

Researchers must assess similarities and differences in colour from an animal's eye view when investigating hypotheses in ecology, evolution and behaviour. Nervous systems generate colour perceptions by comparing the responses of different spectral classes of photoreceptor through colour opponent mechanisms, and the performance of these mechanisms is limited by photoreceptor noise. Accordingly, the receptor noise limited (RNL) colour distance model of Vorobyev and Osorio (Vorobyev & Osorio 1998 Proc. R. Soc. Lond. B 265 , 351–358 ( doi:10.1098/rspb.1998.0302 )) generates predictions about the discriminability of colours that agree with behavioural data, and consequently it has found wide application in studies of animal colour vision. Vorobyev and Osorio (1998) provide equations to calculate RNL colour distances for animals with di-, tri- and tetrachromatic vision, which is adequate for many species. However, researchers may sometimes wish to compute RNL colour distances for potentially more complex colour visual systems. Thus, we derive a simple, single formula for the computation of RNL distance between two measurements of colour, equivalent to the published di-, tri- and tetrachromatic equations of Vorobyev and Osorio (1998), and valid for colour visual systems with any number of types of noisy photoreceptors. This formula will allow the easy application of this important colour visual model across the fields of ecology, evolution and behaviour.

scholarly journals Colour thresholds in a coral reef fish

2016 ◽  
Vol 3 (9) ◽  
pp. 160399 ◽  
Author(s):  
C. M. Champ ◽  
M. Vorobyev ◽  
N. J. Marshall
Keyword(s):  
Coral Reef ◽  
Reef Fish ◽  
Colour Vision ◽  
Visible Spectrum ◽  
Reef Fishes ◽  
Colour Discrimination ◽  
Visual Model ◽  
The World ◽  
Different Parts ◽  
Receptor Noise

Coral reef fishes are among the most colourful animals in the world. Given the diversity of lifestyles and habitats on the reef, it is probable that in many instances coloration is a compromise between crypsis and communication. However, human observation of this coloration is biased by our primate visual system. Most animals have visual systems that are ‘tuned’ differently to humans; optimized for different parts of the visible spectrum. To understand reef fish colours, we need to reconstruct the appearance of colourful patterns and backgrounds as they are seen through the eyes of fish. Here, the coral reef associated triggerfish, Rhinecanthus aculeatus , was tested behaviourally to determine the limits of its colour vision. This is the first demonstration of behavioural colour discrimination thresholds in a coral reef species and is a critical step in our understanding of communication and speciation in this vibrant colourful habitat. Fish were trained to discriminate between a reward colour stimulus and series of non-reward colour stimuli and the discrimination thresholds were found to correspond well with predictions based on the receptor noise limited visual model and anatomy of the eye. Colour discrimination abilities of both reef fish and a variety of animals can therefore now be predicted using the parameters described here.

scholarly journals Colour vision and information theory: the receptor noise-limited model implies optimal colour discrimination by opponent channels

2020 ◽  
Author(s):  
Sebastián Risau-Gusman
Keyword(s):  
Colour Vision ◽  
Theoretical Models ◽  
Ideal Observer ◽  
Discrimination Function ◽  
Colour Discrimination ◽  
Biologically Relevant ◽  
Visual Systems ◽  
The World ◽  
The One ◽  
Receptor Noise

AbstractIn order to interpret animal behaviour we need to understand how they see the world. As colour discrimination is almost impossible to test directly in animals, it is important to develop theoretical models based in the properties of visual systems. One of the most successful is the receptor noise-limited (RNL) model, which depends only on the level of noise in photoreceptors and opponent mechanisms. Here optimal colour discrimination properties are obtained using information theoretical tools, for the early stages of visual systems with and without colour opponent mechanisms. For most biologically relevant conditions the optimal discrimination function of an ideal observer coincides with the one obtained with the RNL model. Many variants of the model can be cast into the same framework, which permits meaningful comparisons across species. For example, it is shown that the presence of opponency seems to be the preferred hypothesis for bees, but not for budgerigars. Since this is a consequence of the presence of oil droplets, this could also be true for most other species of birds.

scholarly journals Thresholds and noise limitations of colour vision in dim light

2017 ◽  
Vol 372 (1717) ◽  
pp. 20160065 ◽  
Author(s):  
Almut Kelber ◽  
Carola Yovanovich ◽  
Peter Olsson
Keyword(s):  
Shot Noise ◽  
Colour Vision ◽  
Absolute Threshold ◽  
Colour Discrimination ◽  
Dark Noise ◽  
Visual Threshold ◽  
Light Intensities ◽  
Purkinje Shift ◽  
Dim Light ◽  
Receptor Noise

Colour discrimination is based on opponent photoreceptor interactions, and limited by receptor noise. In dim light, photon shot noise impairs colour vision, and in vertebrates, the absolute threshold of colour vision is set by dark noise in cones. Nocturnal insects (e.g. moths and nocturnal bees) and vertebrates lacking rods (geckos) have adaptations to reduce receptor noise and use chromatic vision even in very dim light. In contrast, vertebrates with duplex retinae use colour-blind rod vision when noisy cone signals become unreliable, and their transition from cone- to rod-based vision is marked by the Purkinje shift. Rod–cone interactions have not been shown to improve colour vision in dim light, but may contribute to colour vision in mesopic light intensities. Frogs and toads that have two types of rods use opponent signals from these rods to control phototaxis even at their visual threshold. However, for tasks such as prey or mate choice, their colour discrimination abilities fail at brighter light intensities, similar to other vertebrates, probably limited by the dark noise in cones. This article is part of the themed issue 'Vision in dim light’.

scholarly journals The visual ecology of Holocentridae, a nocturnal coral reef fish family with a deep-sea-like multibank retina

2020 ◽  
pp. jeb.233098
Author(s):  
Fanny de Busserolles ◽  
Fabio Cortesi ◽  
Lily Fogg ◽  
Sara M. Stieb ◽  
Martin Luehrmann ◽  
...  
Keyword(s):  
Visual System ◽  
Reef Fish ◽  
Deep Sea ◽  
Colour Vision ◽  
Ganglion Cells ◽  
Light Sensitivity ◽  
Fish Family ◽  
Visual Systems ◽  
Retinal Topography ◽  
Dim Light

The visual systems of teleost fishes usually match their habitats and lifestyles. Since coral reefs are bright and colourful environments, the visual systems of their diurnal inhabitants have been more extensively studied than those of nocturnal species. In order to fill this knowledge gap, we conducted a detailed investigation of the visual system of the nocturnal reef fish family Holocentridae. Results showed that the visual system of holocentrids is well adapted to their nocturnal lifestyle with a rod-dominated retina. Surprisingly, rods in all species were arranged into 6-17 well-defined banks, a feature most commonly found in deep-sea fishes, that may increase the light sensitivity of the eye and/or allow colour discrimination in dim-light. Holocentrids also have the potential for dichromatic colour vision during the day with the presence of at least two spectrally different cone types: single cones expressing the blue-sensitive SWS2A gene, and double cones expressing one or two green-sensitive RH2 genes. Some differences were observed between the two subfamilies, with Holocentrinae (squirrelfish) having a slightly more developed photopic visual system than Myripristinae (soldierfish). Moreover, retinal topography of both ganglion cells and cone photoreceptors showed specific patterns for each cell type, likely highlighting different visual demands at different times of the day, such as feeding. Overall, their well-developed scotopic visual systems and the ease of catching and maintaining holocentrids in aquaria, make them ideal models to investigate teleost dim-light vision and more particularly shed light on the function of the multibank retina and its potential for dim-light colour vision.

scholarly journals Coevolution of coloration and colour vision?

2017 ◽  
Vol 372 (1724) ◽  
pp. 20160338 ◽  
Author(s):  
Olle Lind ◽  
Miriam J. Henze ◽  
Almut Kelber ◽  
Daniel Osorio
Keyword(s):  
Colour Vision ◽  
Evolutionary Relationship ◽  
Evolutionary Significance ◽  
Adaptive Landscape ◽  
Phenotypic Differences ◽  
Visual Systems ◽  
Future Work ◽  
Colour Signals ◽  
Perception Function ◽  
Key Characters

The evolutionary relationship between signals and animal senses has broad significance, with potential consequences for speciation, and for the efficacy and honesty of biological communication. Here we outline current understanding of the diversity of colour vision in two contrasting groups: the phylogenetically conservative birds, and the more variable butterflies. Evidence for coevolution of colour signals and vision exists in both groups, but is limited to observations of phenotypic differences between visual systems, which might be correlated with coloration. Here, to illustrate how one might interpret the evolutionary significance of such differences, we used colour vision modelling based on an avian eye to evaluate the effects of variation in three key characters: photoreceptor spectral sensitivity, oil droplet pigmentation and the proportions of different photoreceptor types. The models predict that physiologically realistic changes in any one character will have little effect, but complementary shifts in all three can substantially affect discriminability of three types of natural spectra. These observations about the adaptive landscape of colour vision may help to explain the general conservatism of photoreceptor spectral sensitivities in birds. This approach can be extended to other types of eye and spectra to inform future work on coevolution of coloration and colour vision. This article is part of the themed issue ‘Animal coloration: production, perception, function and application’.

Bird colour vision: behavioural thresholds reveal receptor noise

2015 ◽  
Vol 218 (2) ◽  
pp. 184-193 ◽  
Author(s):  
P. Olsson ◽  
O. Lind ◽  
A. Kelber
Keyword(s):  
Colour Vision ◽  
Receptor Noise

scholarly journals Visual adaptation and face perception

2011 ◽  
Vol 366 (1571) ◽  
pp. 1702-1725 ◽  
Author(s):  
Michael A. Webster ◽  
Donald I. A. MacLeod
Keyword(s):  
Face Perception ◽  
Visual Processing ◽  
Neural Coding ◽  
Colour Vision ◽  
Functional Organization ◽  
Visual Adaptation ◽  
Human Face ◽  
After Effects ◽  
Coding Schemes ◽  
Similarities And Differences

The appearance of faces can be strongly affected by the characteristics of faces viewed previously. These perceptual after-effects reflect processes of sensory adaptation that are found throughout the visual system, but which have been considered only relatively recently in the context of higher level perceptual judgements. In this review, we explore the consequences of adaptation for human face perception, and the implications of adaptation for understanding the neural-coding schemes underlying the visual representation of faces. The properties of face after-effects suggest that they, in part, reflect response changes at high and possibly face-specific levels of visual processing. Yet, the form of the after-effects and the norm-based codes that they point to show many parallels with the adaptations and functional organization that are thought to underlie the encoding of perceptual attributes like colour. The nature and basis for human colour vision have been studied extensively, and we draw on ideas and principles that have been developed to account for norms and normalization in colour vision to consider potential similarities and differences in the representation and adaptation of faces.

scholarly journals Does conspicuousness scale linearly with colour distance? A test using reef fish

2020 ◽  
Vol 287 (1935) ◽  
pp. 20201456
Author(s):  
Carl Santiago ◽  
Naomi F. Green ◽  
Nadia Hamilton ◽  
John A. Endler ◽  
Daniel C. Osorio ◽  
...  
Keyword(s):  
Reef Fish ◽  
Just Noticeable Difference ◽  
Colour Space ◽  
Perceptual Distance ◽  
The One ◽  
The Relationship ◽  
Colour Signals ◽  
Behavioural Evidence ◽  
Receptor Noise ◽  
Colour Distance

To be effective, animal colour signals must attract attention—and therefore need to be conspicuous. To understand the signal function, it is useful to evaluate their conspicuousness to relevant viewers under various environmental conditions, including when visual scenes are cluttered by objects of varying colour. A widely used metric of colour difference (Δ S ) is based on the receptor noise limited (RNL) model, which was originally proposed to determine when two similar colours appear different from one another, termed the discrimination threshold (or just noticeable difference). Estimates of the perceptual distances between colours that exceed this threshold—termed ‘suprathreshold’ colour differences—often assume that a colour's conspicuousness scales linearly with colour distance, and that this scale is independent of the direction in colour space. Currently, there is little behavioural evidence to support these assumptions. This study evaluated the relationship between Δ S and conspicuousness in suprathreshold colours using an Ishihara-style test with a coral reef fish, Rhinecanthus aculeatus . As our measure of conspicuousness, we tested whether fish, when presented with two colourful targets, preferred to peck at the one with a greater Δ S ­ from the average distractor colour. We found the relationship between Δ S and conspicuousness followed­­ a sigmoidal function, with high Δ S colours perceived as equally conspicuous. We found that the relationship between Δ S and conspicuousness varied across colour space (i.e. for different hues). The sigmoidal detectability curve was little affected by colour variation in the background or when colour distance was calculated using a model that does not incorporate receptor noise. These results suggest that the RNL model may provide accurate estimates for perceptual distance for small suprathreshold distance colours, even in complex viewing environments, but must be used with caution with perceptual distances exceeding­ ­10 Δ S .

scholarly journals Experimental evidence that primate trichromacy is well suited for detecting primate social colour signals

2017 ◽  
Vol 284 (1856) ◽  
pp. 20162458 ◽  
Author(s):  
Chihiro Hiramatsu ◽  
Amanda D. Melin ◽  
William L. Allen ◽  
Constance Dubuc ◽  
James P. Higham
Keyword(s):  
Experimental Evidence ◽  
Spectral Reflectance ◽  
Colour Vision ◽  
Macaque Monkeys ◽  
Visual Systems ◽  
Cone Pigments ◽  
Information Detection ◽  
Empirical Tests ◽  
Colour Signals ◽  
Better Than

Primate trichromatic colour vision has been hypothesized to be well tuned for detecting variation in facial coloration, which could be due to selection on either signal wavelengths or the sensitivities of the photoreceptors themselves. We provide one of the first empirical tests of this idea by asking whether, when compared with other visual systems, the information obtained through primate trichromatic vision confers an improved ability to detect the changes in facial colour that female macaque monkeys exhibit when they are proceptive. We presented pairs of digital images of faces of the same monkey to human observers and asked them to select the proceptive face. We tested images that simulated what would be seen by common catarrhine trichromatic vision, two additional trichromatic conditions and three dichromatic conditions. Performance under conditions of common catarrhine trichromacy, and trichromacy with narrowly separated LM cone pigments (common in female platyrrhines), was better than for evenly spaced trichromacy or for any of the dichromatic conditions. These results suggest that primate trichromatic colour vision confers excellent ability to detect meaningful variation in primate face colour. This is consistent with the hypothesis that social information detection has acted on either primate signal spectral reflectance or photoreceptor spectral tuning, or both.

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