scholarly journals Perceptual organization across spatial scales in natural images: Seeing more high spatial frequency than meet the eyes

2010 ◽  
Vol 8 (6) ◽  
pp. 71-71 ◽  
Author(s):  
A. Oliva ◽  
T. F. Brady
Keyword(s):  
Spatial Frequency ◽  
Perceptual Organization ◽  
Spatial Scales ◽  
High Spatial Frequency ◽  
Natural Images

Increased fusiform area activation in schizophrenia during processing of spatial frequency-degraded faces, as revealed by fMRI

2009 ◽  
Vol 40 (7) ◽  
pp. 1159-1169 ◽  
Author(s):  
S. M. Silverstein ◽  
S. D. All ◽  
R. Kasi ◽  
S. Berten ◽  
B. Essex ◽  
...  
Keyword(s):  
Spatial Frequency ◽  
Perceptual Organization ◽  
Face Processing ◽  
Gender Discrimination ◽  
High Spatial Frequency ◽  
Superior Performance ◽  
Full Spectrum ◽  
Frequency Information ◽  
Form Processing ◽  
Patient Performance

BackgroundPeople with schizophrenia demonstrate perceptual organization impairments, and these are thought to contribute to their face processing difficulties.MethodWe examined the neural substrates of emotionally neutral face processing in schizophrenia by investigating neural activity under three stimulus conditions: faces characterized by the full spectrum of spatial frequencies, faces with low spatial frequency information removed [high spatial frequency (HSF) condition], and faces with high spatial frequency information removed [low spatial frequency (LSF) condition]. Face perception in the HSF condition is more reliant on local feature processing whereas perception in the LSF condition requires greater reliance on global form processing. Past studies of perceptual organization in schizophrenia indicate that patients perform relatively more poorly with degraded stimuli but also that, when global information is absent, patients may perform better than controls because of their relatively increased ability to initially process individual features. Therefore, we hypothesized that people with schizophrenia (n=14) would demonstrate greater face processing difficulties than controls (n=13) in the LSF condition, whereas they would demonstrate a smaller difference or superior performance in the HSF condition.ResultsIn a gender-discrimination task, behavioral data indicated high levels of accuracy for both groups, with a trend toward an interaction involving higher patient performance in the HSF condition and poorer patient performance in the LSF condition. Patients demonstrated greater activity in the fusiform gyrus compared to controls in both degraded conditions.ConclusionsThese data suggest that impairments in basic integration abilities may be compensated for by relatively increased activity in this region.

scholarly journals Hybrid motion illusions as examples of perceptual conflict

2021 ◽  
Vol 2 ◽  
Author(s):  
Arthur Shapiro
Keyword(s):  
Spatial Frequency ◽  
Spatial Scales ◽  
High Spatial Frequency ◽  
Natural World ◽  
Fine Scale ◽  
Frequency Content ◽  
Coarse Scale ◽  
Trade Offs ◽  
Spatial Frequencies ◽  
Contrast Information

Shapiro and Hedjar (2019) proposed a shift in the definition of illusion, from ‘differences between perception and reality’ to ‘conflicts between possible constructions of reality’. This paper builds on this idea by presenting a series of motion hybrid images that juxtapose fine scale contrast (high spatial frequency content) with coarse scale contrast-generated motion (low spatial frequency content). As is the case for static hybrid images, under normal viewing conditions the fine scale contrast determines the perception of motion hybrid images; however, if the motion hybrid image is blurred or viewed from a distance, the perception is determined by the coarse scale contrast. The fine scale contrast therefore masks the perception of motion (and sometimes depth) produced by the coarser scale contrast. Since the unblurred movies contain both fine and coarse scale contrast information, but the blurred movies contain only coarse scale contrast information, cells in the brain that respond to low spatial frequencies should respond equally to both blurred and unblurred movies. Since people undoubtedly differ in the optics of their eyes and most likely in the neural processes that resolve conflict across scales, the paper suggests that motion hybrid images illustrate trade-offs between spatial scales that are important for understanding individual differences in perceptions of the natural world.

Discrimination of Changes in the Slopes of the Amplitude Spectra of Natural Images: Band-Limited Contrast and Psychometric Functions

Perception ◽  
1997 ◽  
Vol 26 (8) ◽  
pp. 1011-1025 ◽  
Author(s):  
David J Tolhurst ◽  
Yoav Tadmor
Keyword(s):  
Spatial Frequency ◽  
Discrimination Task ◽  
Spatial Scales ◽  
Natural Images ◽  
Natural Scenes ◽  
Local Contrast ◽  
Frequency Bands ◽  
Amplitude Spectra ◽  
Lower Frequency Band ◽  
Band Limited

Thresholds were measured for discriminating changes in the slopes of the amplitude spectra of stimuli derived from photographs of natural scenes and from random-luminance patterns. The variety and magnitudes of the thresholds could be explained by a model based on the discrimination of the changes in band-limited local contrast. Different spatial scales of local contrast (or different spatial-frequency bands of about 1 octave) were implicated for different reference spectral slopes; the model implicated a lower frequency-band for stimuli with shallower amplitude spectra. The implications of the model were tested experimentally by using stimuli in which the spectra were changed within restricted spatial-frequency bands. When the amplitude spectra of the test and reference stimuli differed only within the implicated frequency bands, thresholds were affected little. However, when the test and reference spectra differed at all frequencies except those in the implicated bands, the thresholds were elevated markedly. The forms of the psychometric functions for the discrimination task were entirely compatible with the hypothesis that the task relies upon the ability to discriminate changes of contrast. The Weibull functions fitted to the data had slope parameters (β) in the range 1 to 3, compatible with discrimination of low (but suprathreshold) contrasts.

Spatial Frequency Tolerant Visual Object Representations in the Human Ventral and Dorsal Visual Processing Pathways

2019 ◽  
Vol 31 (1) ◽  
pp. 49-63 ◽  
Author(s):  
Maryam Vaziri-Pashkam ◽  
JohnMark Taylor ◽  
Yaoda Xu
Keyword(s):  
Spatial Frequency ◽  
Visual Processing ◽  
Spatial Scales ◽  
High Spatial Frequency ◽  
Visual Input ◽  
Differential Sensitivity ◽  
Visual Object ◽  
Object Representations ◽  
Object Category ◽  
Object Categories

Primate ventral and dorsal visual pathways both contain visual object representations. Dorsal regions receive more input from magnocellular system while ventral regions receive inputs from both magnocellular and parvocellular systems. Due to potential differences in the spatial sensitivites of manocellular and parvocellular systems, object representations in ventral and dorsal regions may differ in how they represent visual input from different spatial scales. To test this prediction, we asked observers to view blocks of images from six object categories, shown in full spectrum, high spatial frequency (SF), or low SF. We found robust object category decoding in all SF conditions as well as SF decoding in nearly all the early visual, ventral, and dorsal regions examined. Cross-SF decoding further revealed that object category representations in all regions exhibited substantial tolerance across the SF components. No difference between ventral and dorsal regions was found in their preference for the different SF components. Further comparisons revealed that, whereas differences in the SF component separated object category representations in early visual areas, such a separation was much smaller in downstream ventral and dorsal regions. In those regions, variations among the object categories played a more significant role in shaping the visual representational structures. Our findings show that ventral and dorsal regions are similar in how they represent visual input from different spatial scales and argue against a dissociation of these regions based on differential sensitivity to different SFs.

Directional shifts in the barber pole illusion: Effects of spatial frequency, spatial adaptation, and lateral masking

2006 ◽  
Vol 23 (5) ◽  
pp. 729-739 ◽  
Author(s):  
CHRISTOPHE LALANNE ◽  
JEAN LORENCEAU
Keyword(s):  
Spatial Frequency ◽  
Spatial Scales ◽  
Receptive Fields ◽  
High Spatial Frequency ◽  
Motion Processing ◽  
Lateral Masking ◽  
Contrast Adaptation ◽  
Neuronal Processes ◽  
Process Line ◽  
Line Ending

We report the results of psychophysical experiments with the so-called barber pole stimulus providing new insights on the neuronal processes underlying the analysis of moving features such as terminators or line-endings. In experiment 1, we show that the perceived direction of a barber pole stimulus, induced by line-ending motion, is highly dependent on the spatial frequency and contrast of the grating stimulus: perceived direction is shifted away from the barber pole illusion at high spatial frequency in a contrast dependent way, suggesting that line-ends are not processed at high spatial scales. In subsequent experiments, we use a contrast adaptation paradigm and a masking paradigm in an attempt to assess the spatial structure and location of the receptive fields that process line-endings. We show that the adapting stimulus that weakens most the barber pole illusion is localized within the barber pole stimulus and not at line-endings' locations. Current models of line-endings' motion processing are discussed in the light of these psychophysical results.

scholarly journals Information redundancy across spatial scales modulates early visual cortical processing

2021 ◽  
Author(s):  
Kirsten Petras ◽  
Sanne Ten Oever ◽  
Sarang S. Dalal ◽  
Valerie Goffaux
Keyword(s):  
Spatial Frequency ◽  
Spatial Scales ◽  
High Spatial Frequency ◽  
Information Redundancy ◽  
Time Frequency ◽  
Early Visual Cortex ◽  
Efficient Integration ◽  
Efficient Processing ◽  
Visual Cortical ◽  
Human Faces

Visual images contain redundant information across spatial scales where low spatial frequency contrast is informative towards the location and likely content of high spatial frequency detail. Previous research suggests that the visual system makes use of those redundancies to facilitate efficient processing. In this framework, a fast, initial analysis of low-spatial frequency (LSF) information guides the slower and later processing of high spatial frequency (HSF) detail. Here, we used multivariate classification as well as time-frequency analysis of MEG responses to the viewing of intact and phase scrambled images of human faces to demonstrate that the availability of redundant LSF information, as found in broadband intact images, correlates with a reduction in HSF representational dominance in both early and higher-level visual areas as well as a reduction of gamma-band power in early visual cortex. Our results indicate that the cross spatial frequency information redundancy that can be found in all natural images might be a driving factor in the efficient integration of fine image details.

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