scholarly journals Hue-selective elevation in luminance contrast detection threshold following adaptation to luminance-varying gabor patches

2010 ◽  
Vol 2 (7) ◽  
pp. 209-209
Author(s):  
J. L. Hardy ◽  
K. K. Valois
Keyword(s):  
Detection Threshold ◽  
Luminance Contrast ◽  
Contrast Detection

Neurophysiological Contributions to Luminance and Chromatic Mechanisms in a Hyperacuity Task

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 339-339
Author(s):  
L Rüttiger ◽  
B B Lee
Keyword(s):  
Detection Threshold ◽  
Luminance Contrast ◽  
Contrast Threshold ◽  
Psychophysical Data ◽  
Spatial Mechanisms ◽  
Cone Cells

We recently reported (paper presented at ARVO 1997) psychophysical evidence as to contributions of luminance and chromatic mechanism in a hyperacuity task, namely detection of small displacements. Achromatic or chromatic (430, 550, 690 nm) edges were presented on white or chromatic (550 nm) backgrounds, and displacement thresholds measured as a function of luminance contrast. Above 3% (achromatic detection threshold), all conditions yielded nearly identical contrast/threshold curves; we believe a luminance mechanism to be responsible. In chromatic conditions, below 3% contrast, large (>100 s arc) displacements were detectable; presumably chromatic mechanisms are responsible. We have now carried out equivalent physiological experiments. Data were consistent with cells of the magnocellular (MC) pathway underlying the luminance mechanism. Opponent S-cone or parvocellular (PC) cells became responsive to displacements in the chromatic conditions. S-cone cells were very responsive to the 430 nm edge, and responded at low contrasts matching the psychophysical thresholds. L, M-cone opponent cells were responsive to the 690 nm edge, but less so than was expected from the psychophysical data. Our data suggest MC-cells underlie a luminance hyperacuity mechanism. Additional factors (eg cell numerosity) may have to be considered for chromatic spatial mechanisms.

scholarly journals Modulation of contrast detection threshold by the configuration and contrast of the context

2010 ◽  
Vol 6 (6) ◽  
pp. 760-760
Author(s):  
L. Jingling ◽  
L. Zhaoping
Keyword(s):  
Detection Threshold ◽  
Contrast Detection

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.

The Perceived Strength of Motion-Defined Edges

Perception ◽  
1993 ◽  
Vol 22 (10) ◽  
pp. 1195-1204 ◽  
Author(s):  
Tom Banton ◽  
Dennis M Levi
Keyword(s):  
Detection Threshold ◽  
Luminance Contrast ◽  
Stage Model ◽  
Stimulus Strength ◽  
Matching Method ◽  
Edge Strength ◽  
Single Scale ◽  
Visual Tasks ◽  
Dot Density ◽  
Contour Strength

Performance on visual tasks involving the use of motion-defined contours is likely to depend on stimulus strength, but presently there are no empirical or experimental assessments of motion-defined contour strength. Therefore, a matching method was used to estimate the strength of suprathreshold motion-defined edges on a luminance-contrast scale. The perceived strength of a motion-defined contour was expressed as an equivalent luminance contrast; this allowed the use of a single scale which accommodates diverse motion-defined stimuli. Motion-defined edge strength estimated in this manner was an inverted U-shaped function of dot density and dot velocity, and spanned at least a fivefold range of edge strengths. For one observer, maximum motion-defined edge strength was equivalent to 79% luminance contrast, at least thirteen times the contrast detection threshold. The results are interpreted via a simple two-stage model for perceiving motion-defined edges.

scholarly journals Eccentricity dependence of orientation anisotropy of surround suppression of contrast-detection threshold

2018 ◽  
Vol 18 (7) ◽  
pp. 5 ◽  
Author(s):  
Menaka S. Malavita ◽  
Trichur R. Vidyasagar ◽  
Allison M. McKendrick
Keyword(s):  
Detection Threshold ◽  
Surround Suppression ◽  
Contrast Detection ◽  
Orientation Anisotropy

scholarly journals Trend of Contrast Detection Threshold with and without Localization

2013 ◽  
Vol 26 (6) ◽  
pp. 1099-1106 ◽  
Author(s):  
David L. Leong ◽  
Louise Rainford ◽  
Tamara Miner Haygood ◽  
Gary J. Whitman ◽  
William R. Geiser ◽  
...  
Keyword(s):  
Detection Threshold ◽  
Contrast Detection

DICOM GSPS affects on contrast detection threshold

2010 ◽  
Author(s):  
David L. Leong ◽  
Tamara Miner Haygood ◽  
Gary J. Whitman ◽  
Selin Carkaci ◽  
Philip M. Tchou ◽  
...  
Keyword(s):  
Detection Threshold ◽  
Contrast Detection

Long-Lasting Detection Facilitation Induced by Gabor Flankers

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 155-155
Author(s):  
Y Tanaka ◽  
D Sagi
Keyword(s):  
Time Course ◽  
Detection Threshold ◽  
Stimulus Onset ◽  
Long Term Memory ◽  
High Contrast ◽  
Spatial Filters ◽  
Contrast Detection ◽  
Separation Threshold ◽  
Sensitivity Changes

Contrast detection threshold of a Gabor signal (GS) is enhanced in the presence of high contrast GS flankers. Repetitive performance of the task induces contrast sensitivity changes on different time scales: minutes when using mental imagery, and weeks in the context of perceptual learning. We tested the time course of lateral enhancement within a single trial, using a forward masking technique. Contrast detection thresholds were measured (2AFC) for a foveal GS target presented briefly (32 ms) preceded by a presentation (80 ms) of two high-contrast GS flankers, with stimulus onset asynchrony (SOA) varying from 0 to 3600 ms. Using target-to-mask separation of 3\lambda and 12\lambda (\lambda =18°, GS wavelength), we found that the 3\lambda separation GS flankers decreased target threshold by 0.25 log units at SOA=0 and by 0.17 log units at 3600 ms. At 12\lambda separation, threshold decreased by 0.11 log units at SOA=0 and by 0.14 log units at 3600 ms. Long-term and short-term enhancements showed similar dependence on stimulus configuration (maximal for collinear target and masks) and local parameters (orientation and spatial frequency differences between target and flankers). The results imply that spatial filters in early vision retain an input trace for as long as a few seconds (up to 14.4 seconds tested). This trace may subserve the consolidation of filter activity into long-term memory.

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