scholarly journals More than noise: context-dependent luminance contrast discrimination in a coral reef fish (Rhinecanthus aculeatus)

2020 ◽  
Vol 223 (21) ◽  
pp. jeb232090
Author(s):  
Cedric P. van den Berg ◽  
Michelle Hollenkamp ◽  
Laurie J. Mitchell ◽  
Erin J. Watson ◽  
Naomi F. Green ◽  
...  
Keyword(s):  
Luminance Contrast ◽  
Individual Species ◽  
Motion Pattern ◽  
Diverse Range ◽  
Bright Spots ◽  
Context Dependent ◽  
Luminance Discrimination ◽  
Contrast Perception ◽  
Contrast Discrimination ◽  
Contrast Thresholds

ABSTRACTAchromatic (luminance) vision is used by animals to perceive motion, pattern, space and texture. Luminance contrast sensitivity thresholds are often poorly characterised for individual species and are applied across a diverse range of perceptual contexts using over-simplified assumptions of an animal's visual system. Such thresholds are often estimated using the receptor noise limited model (RNL). However, the suitability of the RNL model to describe luminance contrast perception remains poorly tested. Here, we investigated context-dependent luminance discrimination using triggerfish (Rhinecanthus aculeatus) presented with large achromatic stimuli (spots) against uniform achromatic backgrounds of varying absolute and relative contrasts. ‘Dark’ and ‘bright’ spots were presented against relatively dark and bright backgrounds. We found significant differences in luminance discrimination thresholds across treatments. When measured using Michelson contrast, thresholds for bright spots on a bright background were significantly higher than for other scenarios, and the lowest threshold was found when dark spots were presented on dark backgrounds. Thresholds expressed in Weber contrast revealed lower thresholds for spots darker than their backgrounds, which is consistent with the literature. The RNL model was unable to estimate threshold scaling across scenarios as predicted by the Weber–Fechner law, highlighting limitations in the current use of the RNL model to quantify luminance contrast perception. Our study confirms that luminance contrast discrimination thresholds are context dependent and should therefore be interpreted with caution.

scholarly journals More than noise: Context-dependant luminance contrast discrimination in a coral reef fish (Rhinecanthus aculeatus)

2020 ◽  
Author(s):  
Cedric P. van den Berg ◽  
Michelle Hollenkamp ◽  
Laurie J. Mitchell ◽  
Erin J. Watson ◽  
Naomi F. Green ◽  
...  
Keyword(s):  
Contrast Sensitivity ◽  
Luminance Contrast ◽  
Individual Species ◽  
Diverse Range ◽  
Bright Spots ◽  
Context Dependent ◽  
Luminance Discrimination ◽  
Contrast Perception ◽  
Contrast Discrimination ◽  
Contrast Thresholds

AbstractAchromatic (luminance) vision is used by animals to perceive motion, pattern, space and texture. Luminance contrast sensitivity thresholds are often poorly characterised for individual species and are applied across a diverse range of perceptual contexts using over-simplified assumptions of an animal’s visual system. Such thresholds are often estimated using the Receptor Noise Limited model (RNL) using quantum catch values and estimated noise levels of photoreceptors. However, the suitability of the RNL model to describe luminance contrast perception remains poorly tested.Here, we investigated context-dependent luminance discrimination using triggerfish (Rhinecanthus aculeatus) presented with large achromatic stimuli (spots) against uniform achromatic backgrounds of varying absolute and relative contrasts. ‘Dark’ and ‘bright’ spots were presented against relatively dark and bright backgrounds. We found significant differences in luminance discrimination thresholds across treatments. When measured using Michelson contrast, thresholds for bright spots on a bright background were significantly higher than for other scenarios, and the lowest threshold was found when dark spots were presented on dark backgrounds. Thresholds expressed in Weber contrast revealed increased contrast sensitivity for stimuli darker than their backgrounds, which is consistent with the literature. The RNL model was unable to estimate threshold scaling across scenarios as predicted by the Weber-Fechner law, highlighting limitations in the current use of the RNL model to quantify luminance contrast perception. Our study confirms that luminance contrast discrimination thresholds are context-dependent and should therefore be interpreted with caution.

Color and luminance increment thresholds in poor readers

2008 ◽  
Vol 25 (3) ◽  
pp. 481-486 ◽  
Author(s):  
STEPHEN J. DAIN ◽  
RICHARD A. FLOYD ◽  
ROBERT T. ELLIOT
Keyword(s):  
Luminance Contrast ◽  
Poor Readers ◽  
Chromatic Contrast ◽  
Colored Overlays ◽  
Visual Processes ◽  
Computer Based ◽  
Luminance Increment ◽  
Contrast Discrimination ◽  
Contrast Thresholds ◽  
Higher Sensitivity

The hypotheses of a visual basis to reading disabilities in some children have centered around deficits in the visual processes displaying more transient reponses to stimuli although hyperactivity in the visual processes displaying sustained reponses to stimuli has also been proposed as a mechanism. In addition, there is clear evidence that colored lenses and/or colored overlays and/or colored backgrounds can influence performance in reading and/or may assist in providing comfortable vision for reading and, as a consequence, the ability to maintain reading for longer. As a consequence, it is surprising that the color vision of poor readers is relatively little studied. We assessed luminance increment thresholds and equi-luminous red-green and blue-yellow increment thresholds using a computer based test in central vision and at 10° nasally employing the paradigm pioneered by King-Smith. We examined 35 poor readers (based on the Neale Analysis of Reading) and compared their performance with 35 normal readers matched for age and IQ. Poor readers produced similar luminance contrast thresholds for both foveal and peripheral presentation compared with normals. Similarly, chromatic contrast discrimination for the red/green stimuli was the same in normal and poor readers. However, poor readers had significantly lower thresholds/higher sensitivity for the blue/yellow stimuli, for both foveal and peripheral presentation, compared with normal readers. This hypersensitivity in blue-yellow discrimination may point to why colored lenses and overlays are often found to be effective in assisting many poor readers.

scholarly journals Specificity of the chromatic noise influence on the luminance contrast discrimination to the color vision phenotype

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Bruna Rafaela Silva Sousa ◽  
Terezinha Medeiros Gonçalves Loureiro ◽  
Paulo Roney Kilpp Goulart ◽  
Maria Izabel Tentes Cortes ◽  
Marcelo Fernandes Costa ◽  
...  
Keyword(s):  
Color Vision ◽  
Luminance Contrast ◽  
Color Information ◽  
Noise Masking ◽  
Central Target ◽  
Luminance Threshold ◽  
Color Vision Deficiencies ◽  
Luminance Discrimination ◽  
Contrast Discrimination ◽  
Color Vision Impairment

Abstract Many studies have examined how color and luminance information are processed in the visual system. It has been observed that chromatic noise masked luminance discrimination in trichromats and that luminance thresholds increased as a function of noise saturation. Here, we aimed to compare chromatic noise inhibition on the luminance thresholds of trichromats and subjects with severe deutan or protan losses. Twenty-two age-matched subjects were evaluated, 12 trichromats and 10 with congenital color vision impairment: 5 protanopes/protanomalous, and 5 deuteranopes/deuteranomalous. We used a mosaic of circles containing chromatic noise consisting of 8 chromaticities around protan, deutan, and tritan confusion lines. A subset of the circles differed in the remaining circles by the luminance arising from a C-shaped central target. All the participants were tested in 4 chromatic noise saturation conditions (0.04, 0.02, 0.01, 0.005 u′v′ units) and 1 condition without chromatic noise. We observed that trichromats had an increasing luminance threshold as a function of chromatic noise saturation under all chromatic noise conditions. The subjects with color vision deficiencies displayed no changes in the luminance threshold across the different chromatic noise saturations when the noise was composed of chromaticities close to their color confusion lines (protan and deutan chromatic noise). However, for tritan chromatic noise, they were found to have similar results to the trichromats. The use of chromatic noise masking on luminance threshold estimates could help to simultaneously examine the processing of luminance and color information. A comparison between luminance contrast discrimination obtained from no chromatic and high-saturated chromatic noise conditions could be initially undertaken in this double-duty test.

Impaired Speed Perception but Intact Luminance Contrast Perception in People With One Eye

2013 ◽  
Vol 54 (4) ◽  
pp. 3058 ◽  
Author(s):  
Krista R. Kelly ◽  
Sarah R. Zohar ◽  
Brenda L. Gallie ◽  
Jennifer K. E. Steeves
Keyword(s):  
Luminance Contrast ◽  
Speed Perception ◽  
Contrast Perception

Contrast-coding in amblyopia. II. On the physiological basis of contrast recruitment

1983 ◽  
Vol 217 (1208) ◽  
pp. 331-340 ◽  
Keyword(s):  
Psychological Adaptation ◽  
Visual Development ◽  
Threshold Function ◽  
High Threshold ◽  
Physiological Basis ◽  
Contrast Mechanism ◽  
Anomalous Threshold ◽  
Band Limited ◽  
Contrast Perception ◽  
Contrast Thresholds

The perceptual compensations that result from a disruption to early visual development (amblyopia) were investigated to highlight the adaptative capabilities of normal contrast-coding. In anisometropic and meridional ambylopia, contrast thresholds may be raised without sub­stantial impairment to the perception of high contrasts. This accelerating response linking the anomalous threshold function with normal suprathreshold behaviour is similar to that observed for loudness perception in cases of inner ear damage and termed recruitment. This phenomenon is not purely psychological adaptation to amblyopia because magnitude estimation of contrast change within the ‘recruiting range’ is not disturbed. Three possible physiological explanations for contrast recruit­ment are examined, namely (i) recruitment of different-frequency neu­rons, (ii) recruitment of different-threshold neurons and (iii) a gain change in the response–contrast function of individual neurons. Since contrast­-matching in the presence of band-limited noise designed to raise artificially the threshold of adjacent detectors does not alter the recruiting response, it is unlikely that ‘across-frequency’ recruiting represents an adequate explanation. Similarly, it is argued that since the incremental sensitivity to contrast change is not enhanced in the recruiting region it is also unlikely the amblyopic neurons have steeper response–contrast relations (gain) than normal. The remaining and more likely possibility, in the light of recent neurophysiological findings of separate low and high threshold systems in the primate, is that recruitment in amblyopia occurs across neurons with the same spatial but different threshold characteristics. This suggests that normal contrast perception is subserved by more than one contrast mechanism and that in amblyopia the more sensitive contrast channel (lower threshold) is selectively affected.

scholarly journals Rhythmic modulation of visual contrast discrimination triggered by action

2016 ◽  
Vol 283 (1831) ◽  
pp. 20160692 ◽  
Author(s):  
Alessandro Benedetto ◽  
Donatella Spinelli ◽  
M. Concetta Morrone
Keyword(s):  
Temporal Dynamics ◽  
Luminance Contrast ◽  
Suppression Effect ◽  
Visual Contrast ◽  
Low Luminance ◽  
Brain Rhythm ◽  
Rhythmic Oscillation ◽  
Visual Motor ◽  
Contrast Discrimination ◽  
Different Levels

Recent evidence suggests that ongoing brain oscillations may be instrumental in binding and integrating multisensory signals. In this experiment, we investigated the temporal dynamics of visual–motor integration processes. We show that action modulates sensitivity to visual contrast discrimination in a rhythmic fashion at frequencies of about 5 Hz (in the theta range), for up to 1 s after execution of action. To understand the origin of the oscillations, we measured oscillations in contrast sensitivity at different levels of luminance, which is known to affect the endogenous brain rhythms, boosting the power of alpha-frequencies. We found that the frequency of oscillation in sensitivity increased at low luminance, probably reflecting the shift in mean endogenous brain rhythm towards higher frequencies. Importantly, both at high and at low luminance, contrast discrimination showed a rhythmic motor-induced suppression effect, with the suppression occurring earlier at low luminance. We suggest that oscillations play a key role in sensory–motor integration, and that the motor-induced suppression may reflect the first manifestation of a rhythmic oscillation.

The Binocular Summation of Chromatic Contrast

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 145-145 ◽  
Author(s):  
D R Simmons ◽  
F A A Kingdom
Keyword(s):  
Contrast Sensitivity ◽  
Detection Threshold ◽  
Luminance Contrast ◽  
Binocular Summation ◽  
Chromatic Contrast ◽  
Probability Summation ◽  
Investigative Ophthalmology ◽  
Contrast Thresholds ◽  
Detection Mechanisms ◽  
Neural Summation

The level of binocularity possessed by mechanisms sensitive to chromatic contrast is still unclear. Recent studies of stereopsis and chromatic contrast have suggested that stereopsis is maintained at isoluminance, although the contrast sensitivity and disparity ranges of chromatic stereopsis mechanisms are reduced compared to luminance stereopsis mechanisms. Rose, Blake, and Halpern (1988 Investigative Ophthalmology and Visual Science29 283 – 290) hypothesised a link between binocular summation (ie the superiority of binocular detection over monocular detection) and stereopsis. Is this link maintained with heterochromatic isoluminant stimuli? To address this question, the binocular and monocular contrast thresholds for the detection of 0.5 cycle deg−1 Gabor patches were measured. The stimuli possessed different relative amounts of colour and luminance contrast ranging from isoluminance (red/green) to isochrominance (yellow/black) through intermediate values. It was found that, with these stimuli, binocular detection was well modelled by assuming independent mechanisms sensitive to chromatic contrast and luminance contrast. Furthermore, with isoluminant stimuli, levels of binocular summation were above those expected from probability summation between the eyes, thus providing evidence for binocular neural summation within chromatic detection mechanisms. Given that stereoscopic depth identification is impossible at contrast detection threshold with isoluminant heterochromatic stimuli, these results suggest that the link between stereopsis and levels of binocular neural summation may not be a particularly strong one. These results also provide clear evidence for the binocularity of chromatic detection mechanisms.

scholarly journals Suppression of Luminance Contrast Sensitivity by Weak Color Presentation

2021 ◽  
Vol 15 ◽  
Author(s):  
Ippei Negishi ◽  
Keizo Shinomori
Keyword(s):  
Brain Activity ◽  
Luminance Contrast ◽  
Psychophysical Experiment ◽  
Dorsal Pathway ◽  
Color System ◽  
Ventral Pathway ◽  
Visual Cortices ◽  
Contrast Perception ◽  
Psychophysical Studies ◽  
Lower Saturation

The results of psychophysical studies suggest that color in a visual scene affects luminance contrast perception. In our brain imaging studies we have found evidence of an effect of chromatic information on luminance information. The dependency of saturation on brain activity in the visual cortices was measured by functional magnetic resonance imaging (fMRI) while the subjects were observing visual stimuli consisting of colored patches of various hues manipulated in saturation (Chroma value in the Munsell color system) on an achromatic background. The results indicate that the patches suppressed luminance driven brain activity. Furthermore, the suppression was stronger rather than weaker for patches with lower saturation colors, although suppression was absent when gray patches were presented instead of colored patches. We also measured brain activity while the subjects observed only the patches (on a uniformly black background) and confirmed that the colored patches alone did not give rise to differences in brain activity for different Chroma values. The chromatic information affects the luminance information in V1, since the effect was observed in early visual cortices (V2 and V3) and the ventral pathway (hV4), as well as in the dorsal pathway (V3A/B). In addition, we conducted a psychophysical experiment in which the ability to discriminate luminance contrast on a grating was measured. Discrimination was worse when weak (less saturated) colored patches were attached to the grating than when strong (saturated) colored patches or achromatic patches were attached. The results of both the fMRI and psychophysical experiments were consistent in that the effects of color were greater in the conditions with low saturation colors.

scholarly journals Context dependent learning in contrast discrimination: effects of contrast uncertainty

2010 ◽  
Vol 3 (9) ◽  
pp. 173-173
Author(s):  
D. Sagi ◽  
Y. Adini ◽  
M. Tsodyks ◽  
A. W. Technion
Keyword(s):  
Context Dependent ◽  
Dependent Learning ◽  
Contrast Discrimination
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