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

Background Changes Delay the Perceptual Availability of Form Information

2005 ◽  
Vol 94 (6) ◽  
pp. 4331-4343 ◽  
Author(s):  
Xin Huang ◽  
Seth Blau ◽  
Michael A. Paradiso
Keyword(s):  
Visual Field ◽  
Discrimination Performance ◽  
Background Information ◽  
Orientation Discrimination ◽  
Contrast Threshold ◽  
Backward Masking ◽  
Background Condition ◽  
Common Technique ◽  
Orientation Information ◽  
Static Background

In natural visual situations, unlike most psychophysical experiments, when a new stimulus appears in a portion of the visual field, the surrounding background changes simultaneously. In recordings from macaque V1, we found that a visual stimulus presented simultaneously with a background change evokes a response that is qualitatively different from the response to the same stimulus flashed on a static background. With the changing background, information about stimulus orientation and contrast is significantly delayed compared with the static-background situation. Our physiological results make several predictions that we test in the present paper with human psychophysical experiments. In a backward masking paradigm, a bar stimulus was either flashed onto a static background or presented simultaneously with a change in background luminance or pattern. Subjects discriminated bar orientation or detected that the scene changed before the mask. To achieve an equivalent contrast threshold for orientation discrimination, a longer stimulus-mask onset asynchrony (SOA) was needed in the changing than in the static-background condition; to match the orientation discrimination performance in the static and changing-background conditions at a fixed SOA, a higher bar contrast was needed when the background changed. Moreover, in the changing-background condition, a longer SOA was needed to discriminate bar orientation than to detect the scene change. These results suggest that orientation information is available more slowly when the background changes; orientation information is available earlier as stimulus contrast increases. The psychophysical findings are consistent with our physiological predictions. Compared with the common technique of flashing stimuli onto a static background, the changing-background paradigm may be more similar to natural vision in which saccades bring new stimuli and backgrounds into the visual field.

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.

scholarly journals Investigating the Reliability of Population Receptive Field Size Estimates Using fMRI

2020 ◽  
Vol 14 ◽  
Author(s):  
Agustin Lage-Castellanos ◽  
Giancarlo Valente ◽  
Mario Senden ◽  
Federico De Martino
Keyword(s):  
Receptive Field ◽  
Field Size ◽  
Receptive Field Size ◽  
Size Estimates

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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