scholarly journals Orientation discrimination across the visual field: size scaling estimates at near threshold levels of contrast

2010 ◽  
Vol 3 (9) ◽  
pp. 216-216
Author(s):  
S. L Sally ◽  
R. Gurnsey
Keyword(s):  
Visual Field ◽  
Field Size ◽  
Orientation Discrimination ◽  
Threshold Levels ◽  
Size Scaling ◽  
Near Threshold

scholarly journals Orientation discrimination across the visual field: Size estimates near contrast threshold

2005 ◽  
Vol 67 (4) ◽  
pp. 638-647 ◽  
Author(s):  
Sharon L. Sally ◽  
Frédéric J. A. M. Poirier ◽  
Rick Gurnsey
Keyword(s):  
Visual Field ◽  
Field Size ◽  
Orientation Discrimination ◽  
Contrast Threshold ◽  
Size Estimates

Visual Field Size Criteria for Mobility Rehabilitation Referral

2010 ◽  
Vol 87 (12) ◽  
pp. E948-E957 ◽  
Author(s):  
Jan E. Lovie-Kitchin ◽  
Grace P. Soong ◽  
Shirin E. Hassan ◽  
Russell L. Woods
Keyword(s):  
Visual Field ◽  
Field Size

scholarly journals Visual performance in behaving cats after prenatal unilateral enucleation

1993 ◽  
Vol 90 (23) ◽  
pp. 11142-11146 ◽  
Author(s):  
S Bisti ◽  
C Trimarchi
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
Receptive Field ◽  
Receptive Fields ◽  
Direction Selectivity ◽  
Visual Performance ◽  
Field Size ◽  
Electrophysiological Recordings ◽  
Severe Impairment ◽  
Orientation Columns

Prenatal unilateral enucleation in mammals causes an extensive anatomical reorganization of visual pathways. The remaining eye innervates the entire extent of visual subcortical and cortical areas. Electrophysiological recordings have shown that the retino-geniculate connections are retinotopically organized and geniculate neurones have normal receptive field properties. In area 17 all neurons respond to stimulation of the remaining eye and retinotopy, orientation columns, and direction selectivity are maintained. The only detectable change is a reduction in receptive field size. Are these changes reflected in the visual behavior? We studied visual performance in cats unilaterally enucleated 3 weeks before birth (gestational age at enucleation, 39-42 days). We tested behaviorally the development of visual acuity and, in the adult, the extension of the visual field and the contrast sensitivity. We found no difference between prenatal monocularly enucleated cats and controls in their ability to orient to targets in different positions of the visual field or in their visual acuity (at any age). The major difference between enucleated and control animals was in contrast sensitivity:prenatal enucleated cats present a loss in sensitivity for gratings of low spatial frequency (below 0.5 cycle per degree) as well as a slight increase in sensitivity at middle frequencies. We conclude that prenatal unilateral enucleation causes a selective change in the spatial performance of the remaining eye. We suggest that this change is the result of a reduction in the number of neurones with large receptive fields, possibly due to a severe impairment of the Y system.

Comparison at a Distance

Perception ◽  
10.1068/p3393 ◽  
2003 ◽  
Vol 32 (4) ◽  
pp. 395-414 ◽  
Author(s):  
Marina V Danilova ◽  
John D Mollon
Keyword(s):  
Visual Field ◽  
Spatial Frequency ◽  
Visual System ◽  
Spatial Separation ◽  
Orientation Discrimination ◽  
Human Observer ◽  
Systematic Effect ◽  
Trained Subjects ◽  
Stimulus Attribute ◽  
The Subject

The visual system is known to contain hard-wired mechanisms that compare the values of a given stimulus attribute at adjacent positions in the visual field; but how are comparisons performed when the stimuli are not adjacent? We ask empirically how well a human observer can compare two stimuli that are separated in the visual field. For the stimulus attributes of spatial frequency, contrast, and orientation, we have measured discrimination thresholds as a function of the spatial separation of the discriminanda. The three attributes were studied in separate experiments, but in all cases the target stimuli were briefly presented Gabor patches. The Gabor patches lay on an imaginary circle, which was centred on the fixation point and had a radius of 5 deg of visual angle. Our psychophysical procedures were designed to ensure that the subject actively compared the two stimuli on each presentation, rather than referring just one stimulus to a stored template or criterion. For the cases of spatial frequency and contrast, there was no systematic effect of spatial separation up to 10 deg. We conclude that the subject's judgment does not depend on discontinuity detectors in the early visual system but on more central codes that represent the two stimuli individually. In the case of orientation discrimination, two naïve subjects performed as in the cases of spatial frequency and contrast; but two highly trained subjects showed a systematic increase of threshold with spatial separation, suggesting that they were exploiting a distal mechanism designed to detect the parallelism or non-parallelism of contours.

Effect of Peripheral Visual Field Size upon Visual Search in Children and Adults

Perception ◽  
1980 ◽  
Vol 9 (4) ◽  
pp. 451-455 ◽  
Author(s):  
Naoyuki Osaka
Keyword(s):  
Visual Search ◽  
Visual Field ◽  
Power Function ◽  
Age Groups ◽  
Field Size ◽  
Peripheral Visual Field ◽  
Cube Root ◽  
Age Related

Twenty observers in each of the age groups, three, four, five, and twenty-one years, were asked to identify pictures displayed through five different sizes of peephole. Recognition latency changed as a cube-root power function of aperture area. It was found that latency decreased as age and area increased. However, the exponent of the power function showed little age-related change. Effectiveness of the peripheral visual field size was discussed in terms of magnitude of the exponent.

scholarly journals Useful visual field size for pattern perception

1979 ◽  
Vol 25 (2) ◽  
pp. 119-125 ◽  
Author(s):  
Shinya Saida ◽  
Mitsuo Ikeda
Keyword(s):  
Visual Field ◽  
Pattern Perception ◽  
Field Size
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