scholarly journals Lateral interactions in orientation discrimination: Spatial frequency bandwidths

2004 ◽  
Vol 4 (8) ◽  
pp. 776-776
Author(s):  
L. A. Olzak ◽  
S. H. Gabree ◽  
P. I. Laurinen
Keyword(s):  
Spatial Frequency ◽  
Orientation Discrimination ◽  
Lateral Interactions

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.

Orientation discrimination depends on spatial frequency

1991 ◽  
Vol 31 (7-8) ◽  
pp. 1449-1452 ◽  
Author(s):  
David C. Burr ◽  
Sally-Ann Wijesundra
Keyword(s):  
Spatial Frequency ◽  
Orientation Discrimination

scholarly journals Lateral interactions in schizophrenia: What is the role of spatial frequency?

2014 ◽  
Vol 14 (10) ◽  
pp. 55-55
Author(s):  
B. Keane ◽  
S. Kastner ◽  
D. Paterno ◽  
G. Erlikhman ◽  
S. Silverstein
Keyword(s):  
Spatial Frequency ◽  
Lateral Interactions

scholarly journals Stimulus-dependent contrast sensitivity asymmetries around the visual field

2020 ◽  
Author(s):  
Marc M. Himmelberg ◽  
Jonathan Winawer ◽  
Marisa Carrasco
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Visual Angle ◽  
Individual Variability ◽  
Visual Performance ◽  
Orientation Discrimination ◽  
Stimulus Parameter ◽  
Vertical Meridian ◽  
Visual Tasks ◽  
Systematic Manipulation

AbstractAsymmetries in visual performance at isoeccentric locations are known as performance fields. At a fixed eccentricity, visual performance is best along the horizontal, intermediate along the lower vertical, and poorest along the upper vertical meridian. These performance fields are pervasive across a range of visual tasks, including those mediated by contrast sensitivity. However, contrast performance fields have not been characterized with a systematic manipulation of stimulus spatial frequency, eccentricity, and size; three parameters that constrain contrast sensitivity. Further, individual differences in performance fields measurements have not been assessed. Here, we use an orientation discrimination task to characterize the pattern of contrast sensitivity across four isoeccentric locations along the cardinal meridians, and to examine whether and how this asymmetry pattern changes with systematic manipulation of stimulus spatial frequency (4 cpd to 8 cpd), eccentricity (4.5° to 9°), and size (3° visual angle to 6° visual angle). Our data demonstrate that contrast sensitivity is highest along the horizontal, intermediate along the lower vertical, and poorest along the upper vertical meridian. This pattern is consistent across stimulus parameter manipulations, even though they cause profound shifts in contrast sensitivity. Eccentricity-dependent decreases in contrast sensitivity can be compensated for by scaling stimulus size alone. Moreover, we find that individual variability in the strength of performance field asymmetries is consistent across conditions. This study is the first to systematically and jointly manipulate, and compare, contrast performance fields across spatial frequency, eccentricity, and size, and to address individual variability in performance fields.

scholarly journals Differential effects of endogenous and exogenous attention on sensory tuning

2021 ◽  
Author(s):  
Antonio Fernandez ◽  
Sara Okun ◽  
Marisa Carrasco
Keyword(s):  
Spatial Frequency ◽  
Exogenous Attention ◽  
Orientation Discrimination ◽  
Endogenous Attention ◽  
Differential Effects ◽  
Spatial Frequencies ◽  
Tuning Width ◽  
Visual Tasks ◽  
Within Subjects ◽  
Improved Performance

Covert spatial attention benefits performance in many visual tasks (e.g. orientation discrimination, visual search). However, in texture segmentation tasks in which increasing spatial resolution can be detrimental, endogenous and exogenous attention have differential effects on performance. Here we tested whether these differences manifest in sensory representations. We used reverse correlation to assess, in a within-subjects design, whether and how endogenous and exogenous attention differentially alter the representation of orientations and spatial frequencies. The same observers detected a vertical grating embedded in noise following central (endogenous attention; Experiment 1) or peripheral (exogenous attention; Experiment 2) pre-cues. We found that both endogenous and exogenous attention similarly improved performance at the attended location by enhancing the gain of all orientations without changing tuning width. Additionally, endogenous attention enhanced the gain of spatial frequencies above and below the target spatial frequency, whereas exogenous attention preferentially enhanced the gain of spatial frequencies higher than the target spatial frequency. We conclude that these changes in sensory tuning may underlie differential effects of endogenous and exogenous attention on performance.

Orientation Discrimination for Moving Isoluminant and Luminance Targets

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 182-182
Author(s):  
S M Wuerger ◽  
M J Morgan
Keyword(s):  
Standard Deviation ◽  
Spatial Frequency ◽  
Psychometric Function ◽  
Carrier Frequency ◽  
Spatial Vision ◽  
Orientation Discrimination ◽  
Moving Target ◽  
Binary Decision ◽  
Gabor Function

Last year we presented orientation discrimination thresholds for stationary isoluminant red — green and luminance-defined stimuli as a function of spatial frequency and contrast (Wuerger and Morgan, 1995 Perception24 Supplement, 16). The horizontal profile of the stimuli was a Gabor function with a carrier frequency of either 0, 2, or 4 cycles deg−1. Observers made a binary decision (clockwise versus anticlockwise from vertical) and thresholds were defined as the standard deviation of their psychometric function. One main finding was that for carrier frequencies of 2 and 4 cycles deg−1, when stimuli of equal cone contrast are compared, orientation discrimination thresholds for red — green isoluminant stimuli do not differ significantly from the thresholds for luminance-defined stimuli. To further characterise the chromatic mechanisms involved in spatial vision, we assessed orientation discrimination thresholds for isoluminant red — green and luminance-defined Gabor stimuli as a function of the velocity of the moving target. When velocity is increased, orientation discrimination thresholds for isoluminant targets increase more rapidly than the thresholds for luminance targets of identical cone contrasts. We conclude that orientation discrimination is mediated by different chromatic mechanisms with different spatial and temporal sensitivities.

The effects of eccentricity and spatial frequency on the orientation discrimination asymmetry

1998 ◽  
Vol 11 (4) ◽  
pp. 349-366 ◽  
Author(s):  
Frédéric J.A.M. Poirier ◽  
Rick Gurnsey
Keyword(s):  
Spatial Frequency ◽  
Orientation Discrimination
Sign in / Sign up

Export Citation Format

Share Document