Contrast Adaptation and the Spatial Structure of Natural Images

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 174-174
Author(s):  
M A Webster ◽  
O H MacLin ◽  
A L Rees ◽  
V E Raker
Keyword(s):  
Selective Adaptation ◽  
Natural Images ◽  
Spatial Frequencies ◽  
Outdoor Scenes ◽  
Amplitude Spectra ◽  
Contrast Pattern ◽  
Biased Perception ◽  
Face Adaptation ◽  
Contrast Thresholds ◽  
Human Faces

Contrast (pattern-selective) adaptation influences perception by adjusting sensitivity to the prevailing pattern of stimulation. We asked how the state of adaptation might depend on the patterns of spatial contrast typical of the natural visual environment. In one set of experiments, we examined whether adaptation to the characteristic amplitude spectra of natural images (which tend to decrease with frequency as 1/f) induces characteristic changes in contrast sensitivity. Contrast thresholds and suprathreshold contrast matches were measured after adaptation to random samples from an ensemble of images of natural outdoor scenes, or synthetic images formed by filtering the amplitude spectra of noise over a range of slopes. Adaptation differentially reduced sensitivity at low to medium spatial frequencies, but losses were not strongly dependent on the slope of the adapting spectra. In a second set of experiments, we examined the figural aftereffects induced by adaptation to naturalistic stimuli, by adapting and testing with images of human faces, for which small configural changes are highly discriminable. Observers adapted to frontal-view images of faces that were distorted by local expansions or contractions about the centre, and then adjusted distortions in test images to try to select the original face. Adaptation strongly biased perception in a direction opposite to the adapting distortion, with strongest aftereffects when test and adapting stimuli were derived from the same face image. Our results suggest that adaptation to the stimuli encountered in the course of normal viewing may exert ubiquitous and selective influences that are important in characterising the normal operating state of the visual system.

Preliminary Findings Suggesting Cyclic Changes in Visual Contrast Sensitivity during the Menstrual Cycle

1987 ◽  
Vol 64 (2) ◽  
pp. 587-594 ◽  
Author(s):  
Nancy Johnson ◽  
J. Timothy Petersik
Keyword(s):  
Contrast Sensitivity ◽  
Time Series Data ◽  
Series Data ◽  
Control Subjects ◽  
Visual Contrast ◽  
Spatial Frequencies ◽  
Amplitude Spectra ◽  
Cyclic Changes ◽  
Visual Contrast Sensitivity ◽  
Contrast Thresholds

Visual contrast thresholds to both stationary and moving gratings of three spatial frequencies (2, 4, and 16 cyc/deg) were measured over a 32-day period in two women displaying normal menstrual cycles and in two noncycling control subjects. The time-series data of each subject in each condition were Fourier analyzed and the resulting amplitude spectra showed differences between the two sets of subjects. The spectra of the control subjects were relatively flat, whereas those of the experimental subjects showed a number of peaks at several harmonics (periods). Conservative significance tests suggested that the peaks in the spectra of the cycling women were larger than might be expected by chance. The data also suggested that changes in sensitivity were greatest for 4-cyc/deg gratings, those nearest the peak of the normal contrast sensitivity function.

scholarly journals Flexible time course of spatial frequency use during scene categorization

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sandro L. Wiesmann ◽  
Laurent Caplette ◽  
Verena Willenbockel ◽  
Frédéric Gosselin ◽  
Melissa L.-H. Võ
Keyword(s):  
Time Course ◽  
Task Characteristics ◽  
Scene Categorization ◽  
Fine Grained ◽  
Spatial Frequencies ◽  
Outdoor Scenes ◽  
Indoor Scenes ◽  
Fine Pattern ◽  
Late Stages ◽  
Basic Level

AbstractHuman observers can quickly and accurately categorize scenes. This remarkable ability is related to the usage of information at different spatial frequencies (SFs) following a coarse-to-fine pattern: Low SFs, conveying coarse layout information, are thought to be used earlier than high SFs, representing more fine-grained information. Alternatives to this pattern have rarely been considered. Here, we probed all possible SF usage strategies randomly with high resolution in both the SF and time dimensions at two categorization levels. We show that correct basic-level categorizations of indoor scenes are linked to the sampling of relatively high SFs, whereas correct outdoor scene categorizations are predicted by an early use of high SFs and a later use of low SFs (fine-to-coarse pattern of SF usage). Superordinate-level categorizations (indoor vs. outdoor scenes) rely on lower SFs early on, followed by a shift to higher SFs and a subsequent shift back to lower SFs in late stages. In summary, our results show no consistent pattern of SF usage across tasks and only partially replicate the diagnostic SFs found in previous studies. We therefore propose that SF sampling strategies of observers differ with varying stimulus and task characteristics, thus favouring the notion of flexible SF usage.

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.

Coarse-to-fine Categorization of Visual Scenes in Scene-selective Cortex

2014 ◽  
Vol 26 (10) ◽  
pp. 2287-2297 ◽  
Author(s):  
Benoit Musel ◽  
Louise Kauffmann ◽  
Stephen Ramanoël ◽  
Coralie Giavarini ◽  
Nathalie Guyader ◽  
...  
Keyword(s):  
Visual Analysis ◽  
Retrosplenial Cortex ◽  
Dynamic Scenes ◽  
Spatial Frequencies ◽  
Fmri Study ◽  
Outdoor Scenes ◽  
Computational Data ◽  
Cortical Regions ◽  
First Time ◽  
Coarse To Fine

Neurophysiological, behavioral, and computational data indicate that visual analysis may start with the parallel extraction of different elementary attributes at different spatial frequencies and follows a predominantly coarse-to-fine (CtF) processing sequence (low spatial frequencies [LSF] are extracted first, followed by high spatial frequencies [HSF]). Evidence for CtF processing within scene-selective cortical regions is, however, still lacking. In the present fMRI study, we tested whether such processing occurs in three scene-selective cortical regions: the parahippocampal place area (PPA), the retrosplenial cortex, and the occipital place area. Fourteen participants were subjected to functional scans during which they performed a categorization task of indoor versus outdoor scenes using dynamic scene stimuli. Dynamic scenes were composed of six filtered images of the same scene, from LSF to HSF or from HSF to LSF, allowing us to mimic a CtF or the reverse fine-to-coarse (FtC) sequence. Results showed that only the PPA was more activated for CtF than FtC sequences. Equivalent activations were observed for both sequences in the retrosplenial cortex and occipital place area. This study suggests for the first time that CtF sequence processing constitutes the predominant strategy for scene categorization in the PPA.

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.

An Assessment of Decision-Making as a Possible Factor in the Age-Related Loss of Contrast Sensitivity

Perception ◽  
1986 ◽  
Vol 15 (5) ◽  
pp. 541-552 ◽  
Author(s):  
James D Morrison ◽  
James Reilly
Keyword(s):  
Decision Making ◽  
Contrast Sensitivity ◽  
Contrast Threshold ◽  
Sinusoidal Grating ◽  
Hit Rate ◽  
Grating Pattern ◽  
Age Related ◽  
Spatial Frequencies ◽  
Young Subjects ◽  
Contrast Thresholds

The possibility that changes in decision-making may contribute to the age-related decline in contrast sensitivity has been investigated in nineteen young subjects (ages 21–38 years) and twenty-seven old subjects (ages 55–92 years). A signal detection paradigm was employed in which the detection of stationary sinusoidal grating patterns was measured at 3 and 15 cycles deg−1 for a range of contrasts which were psychophysically equivalent for each subject. A decline in contrast sensitivity with age at the spatial frequencies studied was confirmed for contrast thresholds obtained both by the ascending method and from the 50% hit rate for detection of the grating pattern. The criterion adopted for decision-making, expressed as both β and percentage bias, did not change significantly between young and old subjects at 15 cycles deg−1. At 3 cycles deg−1, criterion β did not change significantly at x0.8, x1.0, or x1.2 contrast threshold, but at contrast giving 50% hit rate there was a significant increase with age. The percentage bias increased significantly at contrast threshold but not at 50% hit rate. It is inferred from the results that the loss of contrast sensitivity was not accountable in terms of the adoption of a more conservative criterion by older subjects. Hence visual loss in ageing is attributed to changes within the visual pathway rather than within higher decision-making centres.

Selective Adaptation to Low Spatial Frequencies Does Not Decrease the Mueller-Lyer Illusion

1994 ◽  
Vol 78 (1) ◽  
pp. 339-347
Author(s):  
Janet D. Larsen ◽  
Beth Anne Goldstein
Keyword(s):  
Spatial Frequency ◽  
Visual System ◽  
Major Part ◽  
Selective Adaptation ◽  
Sinusoidal Grating ◽  
Square Wave ◽  
Frequency Information ◽  
Lyer Illusion ◽  
Spatial Frequencies

The idea that low spatial-frequency information in the Mueller-Lyer figure accounts for a major part of the illusion was tested in a series of five studies. In Study 1, subjects were selectively adapted to high or low square-wave spatial-frequency gratings with no difference in the magnitude of illusion they experienced. Similarly, adaptation to sinusoidal grating patterns with either high or low spatial frequency had no effect on the magnitude of illusion experienced (Studies 2 to 5). The failure of adaptation to low spatial-frequency gratings to affect the magnitude of illusion experienced indicates either that the illusion cannot be accounted for by the low spatial-frequency information or that adaptation of the visual system by grating patterns cannot be used to explore any effects of the low spatial frequencies in the figure.

scholarly journals Attention Modifies Spatial Resolution According to Task Demands

2017 ◽  
Vol 28 (3) ◽  
pp. 285-296 ◽  
Author(s):  
Antoine Barbot ◽  
Marisa Carrasco
Keyword(s):  
Spatial Resolution ◽  
High Frequency ◽  
Selective Adaptation ◽  
Task Demands ◽  
Endogenous Attention ◽  
Voluntary Attention ◽  
Improve Performance ◽  
Low Frequencies ◽  
Spatial Frequencies ◽  
Flexible Mechanism

How does visual attention affect spatial resolution? In texture-segmentation tasks, exogenous (involuntary) attention automatically increases resolution at the attended location, which improves performance where resolution is too low (at the periphery) but impairs performance where resolution is already too high (at central locations). Conversely, endogenous (voluntary) attention improves performance at all eccentricities, which suggests a more flexible mechanism. Here, using selective adaptation to spatial frequency, we investigated the mechanism by which endogenous attention benefits performance in resolution tasks. Participants detected a texture target that could appear at several eccentricities. Adapting to high or low spatial frequencies selectively affected performance in a manner consistent with changes in resolution. Moreover, adapting to high, but not low, frequencies mitigated the attentional benefit at central locations where resolution was too high; this shows that attention can improve performance by decreasing resolution. Altogether, our results indicate that endogenous attention benefits performance by modulating the contribution of high-frequency information in order to flexibly adjust spatial resolution according to task demands.

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