Colour Inputs to Random-Dot Stereopsis

Perception ◽  
1992 ◽  
Vol 21 (6) ◽  
pp. 717-729 ◽  
Author(s):  
Geoffrey W Stuart ◽  
Mark Edwards ◽  
Michael L Cook
Keyword(s):  
Luminance Contrast ◽  
Stereoscopic Depth ◽  
Signal To Noise ◽  
Chromatic Contrast ◽  
Magnocellular System ◽  
Colour Contrast ◽  
Random Dot Stereograms ◽  
Photoreceptor Mosaic

Recently it has been claimed by Livingstone and Hubel that, of three anatomically and functionally distinct visual channels (the magnocellular, parvocellular interblob, and blob channels), only the magnocellular channel is involved in the processing of stereoscopic depth. Since the magnocellular system shows little overt colour opponency, the reported loss of the ability to resolve random-dot stereograms defined only by colour contrast seems consistent with this view. However, Julesz observed that reversed-contrast stereograms could be fused if correlated colour information was added. In the present study, ‘noise’ (non-corresponding) pixels were injected into random-dot stereograms in order to increase fusion time. All six subjects tested were able to achieve stereopsis in less than three minutes when there was only correspondence in colour and not in luminance, and three when luminance contrast was completely reversed. This ability depends on information about the direction of colour contrast, not just the presence of chromatic borders. When luminance and chromatic contrast are defined in terms of signal-to-noise ratios at the photoreceptor mosaic, chromatic information plays at least as important a role in stereopsis as does luminance information, suggesting that the magnocellular channel is not uniquely involved.

scholarly journals Luminance contrast and colour contrast related errors in pseudoisochromatic plate identification

Eye ◽  
1997 ◽  
Vol 11 (5) ◽  
pp. 713-716
Author(s):  
Michael Wall ◽  
Paul B Donzis
Keyword(s):  
Luminance Contrast ◽  
Colour Contrast

Stereoscopic Depth Sensitivity Differences between the Crossed and Uncrossed Directions

1989 ◽  
Vol 33 (20) ◽  
pp. 1427-1429 ◽  
Author(s):  
R. Patterson ◽  
G. L. Short ◽  
L. Moe
Keyword(s):  
Stereoscopic Depth ◽  
Random Dot Stereograms ◽  
Depth Sensitivity

This study investigated the temporal sensitivity of crossed and uncrossed stereoscopic mechanisms of 48 observers using stimuli created from dynamic random-dot stereograms. The results showed thresholds were lower and depth was more veridical in the crossed than in the uncrossed direction.

Texture Segregation by Orientation Differences: Colour Sensitive but Not Hue Specific?

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 98-98
Author(s):  
U Leonards ◽  
W Singer
Keyword(s):  
Experimental Psychology ◽  
Human Perception ◽  
Luminance Contrast ◽  
Texture Element ◽  
Feature Maps ◽  
Texture Segregation ◽  
Colour Contrast

Segregation of textures on the basis of orientation differences between texture elements is achieved even when these texture elements differ from their surround only by colour (McIlhagga et al, 1990 Vision Research30 489 – 495). This finding seems to contradict the assumption that colour and orientation are extracted in separate feature maps (eg Treisman and Sato, 1990 Journal of Experimental Psychology: Human Perception and Performance16 459 – 478). To examine whether colour information is evaluated in parallel in different processing streams for the assessment of hue and form, we tested whether texture elements can be segregated if they differ only by specific conjunctions of colour and orientation; texture elements consisted of crosses with their two crossing lines differing in colour. Texture elements defining figure and background had the same coloured composition but the conjunction of colour with the two crossing lines was reversed. Different colour combinations were tested under various luminance contrast conditions, irrespective of the colour combination, segmentation was achieved as long as the two crossing lines of the texture elements differed in luminance. If, however, the different colours of the two crossing lines were approximately equiluminant, segmentation was reduced or impossible. Thus, subjects were able to use for texture segregation conjunctions between luminance and orientation but not between colour and orientation. Our results suggest that colour cannot be associated selectively with differently oriented components of the same texture element. This supports the hypothesis that colour contrast is used in parallel by different processing streams to assess the orientation and hue of contours and reveals limitations in the selectivity with which features are subsequently bound together.

Perception of Movement and Correlation in Stroboscopically Presented Noise Patterns

Perception ◽  
1985 ◽  
Vol 14 (2) ◽  
pp. 209-224 ◽  
Author(s):  
Andrea J van Doorn ◽  
Jan J Koenderink ◽  
Wim A van de Grind
Keyword(s):  
Visual Field ◽  
Signal To Noise Ratio ◽  
Random Noise ◽  
Temporal Correlation ◽  
Motion Aftereffect ◽  
Luminance Contrast ◽  
Signal To Noise ◽  
Field Evidence ◽  
Spatiotemporal Integration ◽  
Moving Pattern

The detection of spatiotemporal correlation in visual displays has been studied with stroboscopically presented random-noise patterns and with a signal-to-noise ratio paradigm in which the moving pattern was masked with spatiotemporal white noise. These methods reveal the ability of the visual system to detect correlation of spatiotemporal structures, rather than luminance contrast. The effects of stroboscopic rate, exposure duration, target size, and the extent of discrete spatial shifts were studied in both the central and the peripheral visual field. Evidence for orientation-selective and speed-selective mechanisms was found, as well as for extensive spatiotemporal integration. Bounds on parameters of spatial and temporal correlation and integration were obtained. The results are similar to those reported earlier, and also extend them. Their relation to results obtained through other paradigms (eg the motion aftereffect) is explored.

Chromatic contrast dependence of reaction time to random-dot stereograms at isoluminance

2015 ◽  
Vol 41 (6) ◽  
pp. 564-570 ◽  
Author(s):  
Kai Lin ◽  
Ningfang Liao ◽  
Dazun Zhao ◽  
Shuwen Dong ◽  
Yasheng Li
Keyword(s):  
Reaction Time ◽  
Chromatic Contrast ◽  
Random Dot Stereograms

scholarly journals Pre-prints

2017 ◽  
Author(s):  
Benjamin de Haas ◽  
D. Samuel Schwarzkopf
Keyword(s):  
Visual Cortex ◽  
Luminance Contrast ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Mapping Data ◽  
Signal To Noise ◽  
Illusory Contours ◽  
Low Contrast ◽  
Early Visual Cortex ◽  
Visual Field Maps

Early visual cortex responds to illusory contours in which abutting lines or collinear edges imply the presence of an occluding surface, as well as to occluded parts of an object. Here we used functional magnetic resonance imaging (fMRI) and population receptive field (pRF) analysis to map retinotopic responses in early visual cortex using bar stimuli defined by illusory contours, occluded parts of a bar, or subtle luminance contrast. All conditions produced retinotopic responses in early visual field maps even though signal-to-noise ratios were very low. We found that signal-to-noise ratios and coherence with independent high-contrast mapping data increased from V1 to V2 to V3. Moreover, we found no differences of signal-to-noise ratios or pRF sizes between the low-contrast luminance and illusion conditions. We propose that all three conditions mapped spatial attention to the bar location rather than activations specifically related to illusory contours or occlusion.

Isoluminant Colour Contrast Does Not Fill in Surfaces

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 40-40
Author(s):  
B Dresp ◽  
C Wehrhahn
Keyword(s):  
Luminance Contrast ◽  
Opposite Polarity ◽  
The Other ◽  
Test Surface ◽  
Colour Contrast ◽  
Mixed Polarity ◽  
Polarity Condition ◽  
Matching Procedure ◽  
The Mean ◽  
Neurophysiological Basis

It has been suggested (Livingstone and Hubel, 1988 Science240 740 – 749) that the ‘colour-blind’ magnocellular pathways generate the neurophysiological basis of surfaces with illusory contours since the latter do not seem to be perceived in inducing configurations of a given colour which is isoluminant with regard to the colour of the background (equiluminant colour contrast). However, psychophysical data allowing us to assess the relative visibility of illusory surfaces in coloured stimuli with luminance contrast compared to configurations with equiluminant colour contrast are not yet available. We designed a colour-matching experiment where ten naive observers had to adjust the intensity of a red illusory surface so that it appeared to match the intensity of the red background. The configurations used were Kanizsa squares with green inducing elements, isoluminant or not with regard to the background. Isoluminance was assessed individually for each observer by means of a classical flicker test. A brightness-matching procedure was applied to configurations of achromatic inducers on a grey background. In this case, the inducers had either all the same contrast polarity (light), or both polarities (light and dark) within a given configuration. Luminance contrast in the achromatic configuration with only one polarity was the same as in the non-isoluminant colour condition. Luminance contrasts of light and dark inducers in the mixed-polarity condition were physically balanced. The results show that the mean point of subjective equality (PSE) of the test surface corresponds to the physical intensity of the background with equiluminant colour contrast only, indicating the absence of an apparent surface in this condition. This result supports the idea that magnocellular pathways in the human visual system mediate the neurophysiological genesis of illusory surfaces. In all the other stimulus conditions, the PSE does not correspond to the physical intensity of the background. Matching ‘errors’ are significantly stronger in the achromatic conditions, but, paradoxically, strongest in the condition with balanced contrasts of opposite polarity. This finding suggests that luminance contrast is not the only determinant of the perceived strength of illusory surfaces.

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.

Chromatic and luminance interactions in spatial contrast signals

1998 ◽  
Vol 15 (4) ◽  
pp. 607-624 ◽  
Author(s):  
JONATHAN D. VICTOR ◽  
KEITH P. PURPURA ◽  
MARY M. CONTE
Keyword(s):  
Linear Combination ◽  
Fundamental Frequency ◽  
Luminance Contrast ◽  
Chromatic Contrast ◽  
Square Wave ◽  
Fundamental Component ◽  
Single Mechanism

We report VEP studies which delineate interactions between chromatic and luminance contrast signals. We examined responses to sinusoidal luminance gratings undergoing 4-Hz square-wave contrast reversal, upon which standing gratings with various admixtures of luminance and chromatic contrast were alternately superimposed and withdrawn. The presence of the standing grating induced a VEP component at the fundamental frequency of the contrast-reversal grating. This VEP component appeared without any appreciable lag, and did not vary in amplitude over the 4 s during which the standing grating was present. The observed fundamental response differed from the fundamental component that would be expected from the known interaction between the luminance component of the standing grating with the modulated grating (Bodis-Wollner et al., 1972; Bobak et al., 1988), in three ways: (1) The fundamental response was not nulled for standing gratings that were isoluminant or near-isoluminant. (2) The chromatic dependence of the fundamental response implied an S-cone input to the interaction. (3) No single mechanism (driven by a linear combination of cone signals) could account quantitatively for the size of this response, particularly when the standing grating strongly modulated two cones in phase.

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