Effects of foveal and eccentric viewing on the resolution and contrast thresholds of individual letters.

2015 ◽  
Vol 8 (2) ◽  
pp. 183-192 ◽  
Author(s):  
Mohd Izzuddin Hairol ◽  
Nor Azizah Abd-Latif ◽  
Patricia Low ◽  
Wei Ping Lim ◽  
Jean Yee Aik ◽  
...  
Keyword(s):  
Eccentric Viewing ◽  
Contrast Thresholds

scholarly journals Contrast thresholds reveal different visual masking functions in humans and praying mantises

2017 ◽  
Author(s):  
Ghaith Tarawneh ◽  
Vivek Nityananda ◽  
Ronny Rosner ◽  
Steven Errington ◽  
William Herbert ◽  
...  
Keyword(s):  
Spatial Frequency ◽  
Motion Detection ◽  
Visual Masking ◽  
High Spatial Frequency ◽  
Visual Noise ◽  
Frequency Noise ◽  
Detection Systems ◽  
Spatial Frequencies ◽  
Summary Statement ◽  
Contrast Thresholds

AbstractRecently, we showed a novel property of the Hassenstein-Reichardt detector: namely, that insect motion detection can be masked by “invisible” noise, i.e. visual noise presented at spatial frequencies to which the animals do not respond when presented as a signal. While this study compared the effect of noise on human and insect motion perception, it used different ways of quantifying masking in two species. This was because the human studies measured contrast thresholds, which were too time-consuming to acquire in the insect given the large number of stimulus parameters examined. Here, we run longer experiments in which we obtained contrast thresholds at just two signal and two noise frequencies. We examine the increase in threshold produced by noise at either the same frequency as the signal, or a different frequency. We do this in both humans and praying mantises (Sphodromantis lineola), enabling us to compare these species directly in the same paradigm. Our results confirm our earlier finding: whereas in humans, visual noise masks much more effectively when presented at the signal spatial frequency, in insects, noise is roughly equivalently effective whether presented at the same frequency or a lower frequency. In both species, visual noise presented at a higher spatial frequency is a less effective mask.Summary StatementWe here show that despite having similar motion detection systems, insects and humans differ in the effect of low and high spatial frequency noise on their contrast thresholds.

Visual Contrast Sensitivity Functions Obtained with Colored and Achromatic Gratings

1979 ◽  
Vol 21 (2) ◽  
pp. 225-228 ◽  
Author(s):  
Michael A. Nelson ◽  
Ronald L. Halberg
Keyword(s):  
Contrast Sensitivity ◽  
Spatial Information ◽  
Sensitivity Functions ◽  
Visual Contrast ◽  
Spatial Frequencies ◽  
Sinusoidal Gratings ◽  
Visual Contrast Sensitivity ◽  
Contrast Thresholds

Threshold contrasts for red, green, and achromatic sinusoidal gratings were measured. Spatial frequencies ranged from 0.25 to 15 cycles/deg. No significant differences in contrast thresholds were found among the three grating types. From this finding it was concluded that, under conditions of normal viewing, no significant differences should be expected in the acquisition of spatial information from monochromatic or achromatic displays of equal resolution.

scholarly journals Contrast thresholds reveal different visual masking functions in humans and praying mantises

Biology Open ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. bio029439 ◽  
Author(s):  
Ghaith Tarawneh ◽  
Vivek Nityananda ◽  
Ronny Rosner ◽  
Steven Errington ◽  
William Herbert ◽  
...  
Keyword(s):  
Visual Masking ◽  
Contrast Thresholds

Spatial vision in strabismic cats

1983 ◽  
Vol 50 (1) ◽  
pp. 287-296 ◽  
Author(s):  
K. Holopigian ◽  
R. Blake
Keyword(s):  
Contrast Sensitivity ◽  
Preceding Paper ◽  
Spatial Vision ◽  
Performance Difference ◽  
Single Class ◽  
Convergent Strabismus ◽  
Contrast Thresholds

Contrast thresholds for detection of stationary and flickering gratings were measured behaviorally for each eye of cats raised with induced convergent strabismus. The performance of the deviating eye was inferior to that of the nondeviating eye when test patterns were stationary. Flicker served to reduce the performance difference between the eyes in two cats but not in a third. These results suggest that strabismus amblyopia may not result from deficits within a single class of neurons. In all strabismic cats the contrast sensitivity of the nondeviating eye was significantly reduced relative to normal cats. These behavioral findings, including the deficits found bilaterally, correspond very well with results from cortical recordings from these and other strabismic cats presented in the preceding paper (7).

scholarly journals The integration of local chromatic motion signals is sensitive to contrast polarity

2011 ◽  
Vol 28 (3) ◽  
pp. 239-246 ◽  
Author(s):  
SOPHIE M. WUERGER ◽  
ALEXA RUPPERTSBERG ◽  
STEPHANIE MALEK ◽  
MARCO BERTAMINI ◽  
JASNA MARTINOVIC
Keyword(s):  
Random Motion ◽  
Coherent Motion ◽  
Global Motion ◽  
Local Motion ◽  
Chromatic Contrast ◽  
Motion Direction ◽  
Contrast Polarity ◽  
Motion Integration ◽  
Integration Mechanisms ◽  
Contrast Thresholds

AbstractGlobal motion integration mechanisms can utilize signals defined by purely chromatic information. Is global motion integration sensitive to the polarity of such color signals? To answer this question, we employed isoluminant random dot kinematograms (RDKs) that contain a single chromatic contrast polarity or two different polarities. Single-polarity RDKs consisted of local motion signals with either a positive or a negative S or L–M component, while in the different-polarity RDKs, half the dots had a positive S or L–M component, and the other half had a negative S or L–M component. In all RDKs, the polarity and the motion direction of the local signals were uncorrelated. Observers discriminated between 50% coherent motion and random motion, and contrast thresholds were obtained for 81% correct responses. Contrast thresholds were obtained for three different dot densities (50, 100, and 200 dots). We report two main findings: (1) dependence on dot density is similar for both contrast polarities (+S vs. −S, +LM vs. −LM) but slightly steeper for S in comparison to LM and (2) thresholds for different-polarity RDKs are significantly higher than for single-polarity RDKs, which is inconsistent with a polarity-blind integration mechanism. We conclude that early motion integration mechanisms are sensitive to the polarity of the local motion signals and do not automatically integrate information across different polarities.

ON VISUAL CONTRAST THRESHOLDS

2009 ◽  
Vol 38 (4) ◽  
pp. 470-484 ◽  
Author(s):  
V. Dreyer
Keyword(s):  
Visual Contrast ◽  
Contrast Thresholds

Pattern and Flicker Detection Examined in Terms of the Nasal — Temporal Division of the Retina

Perception ◽  
1979 ◽  
Vol 8 (5) ◽  
pp. 549-555 ◽  
Author(s):  
Randolph Blake ◽  
Jamie Mills
Keyword(s):  
Spatial Frequency ◽  
Hemispheric Asymmetries ◽  
Contrast Thresholds

Contrast thresholds for the detection of flicker and the detection of pattern were measured for nasal and temporal retinae of each eye separately. While confirming that these two types of thresholds can differ, depending on spatial frequency, the results provide no support for hemiretinal or hemispheric asymmetries in the distribution of the putative pattern and movement channels.

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