Are Spatial Frequencies Integrated from Coarse to Fine?

Perception ◽  
10.1068/p3257 ◽  
2002 ◽  
Vol 31 (8) ◽  
pp. 955-967 ◽  
Author(s):  
Eugene McSorley ◽  
John M Findlay
Keyword(s):  
Spatial Frequency ◽  
Choice Experiment ◽  
Forced Choice ◽  
Square Wave ◽  
Spatial Frequencies ◽  
Task Differences ◽  
Series Of Experiments ◽  
Coarse To Fine ◽  
Opposite Form

The existence of a temporal anisotropy in the integration of spatial frequencies, such that spatial frequencies are integrated more effectively if they are available from low to high through time, has been examined in a series of experiments. In the first experiment, the first three harmonics of a square wave were presented in a low-to-high or a high-to-low sequence in a temporal two-interval forced-choice experiment. Subjects were asked to indicate which sequence appeared to resemble a square wave more. A high-to-low sequence of spatial frequencies was judged to more resemble the target than the low-to-high sequence. These results support a temporal anisotropy in the integration of spatial frequencies of exactly the opposite form to that suggested from previous results. Further experiments established that this was not due to task differences or to subjects basing their decision on the final spatial frequency shown. An interpretation is offered in which an isotropic mechanism for spatial-frequency integration is combined with a recency bias.

Monkeys Show an Oblique Effect

Perception ◽  
1979 ◽  
Vol 8 (3) ◽  
pp. 247-253 ◽  
Author(s):  
Joseph A Bauer ◽  
Donald A Owens ◽  
Joseph Thomas ◽  
Richard Held
Keyword(s):  
Animal Model ◽  
Spatial Frequency ◽  
Oblique Effect ◽  
High Contrast ◽  
Square Wave ◽  
Spatial Frequencies

Monkeys aligned a cursor bar with high-contrast square-wave gratings presented in a variety of orientations. Alignment time increased with increasing spatial frequency from 6 to 24 cycles deg−1 regardless of the orientation of the grating. At higher spatial frequencies, alignment tasks took longer for obliquely oriented gratings than for horizontal and vertical ones. Reducing grating contrast by blurring the image of the 24 cycle deg−1 grating also produced longer alignment times for the obliques. These data indicate that monkeys have an oblique effect similar to that found in humans, implying that the monkey is a useful animal model for investigating the development of meridional anisotropies.

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 Training for object recognition with increasing spatial frequency: A comparison of deep learning with human vision

2021 ◽  
Author(s):  
Lev Kiar Avberšek ◽  
Astrid Zeman ◽  
Hans P. Op de Beeck
Keyword(s):  
Spatial Frequency ◽  
Poor Performance ◽  
Visual Input ◽  
Human Vision ◽  
Striking Similarity ◽  
Deep Convolutional Neural Networks ◽  
Frequency Information ◽  
Spatial Frequencies ◽  
Wide Range ◽  
Coarse To Fine

AbstractThe ontogenetic development of human vision, and the real-time neural processing of visual input, both exhibit a striking similarity – a sensitivity towards spatial frequencies that progress in a coarse-to-fine manner. During early human development, sensitivity for higher spatial frequencies increases with age. In adulthood, when humans receive new visual input, low spatial frequencies are typically processed first before subsequently guiding the processing of higher spatial frequencies. We investigated to what extent this coarse-to-fine progression might impact visual representations in artificial vision and compared this to adult human representations. We simulated the coarse-to-fine progression of image processing in deep convolutional neural networks (CNNs) by gradually increasing spatial frequency information during training. We compared CNN performance, after standard and coarse-to-fine training, with a wide range of datasets from behavioural and neuroimaging experiments. In contrast to humans, CNNs that are trained using the standard protocol are very insensitive to low spatial frequency information, showing very poor performance in being able to classify such object images. By training CNNs using our coarse-to-fine method, we improved the classification accuracy of CNNs from 0% to 32% on low-pass filtered images taken from the ImageNet dataset. When comparing differently trained networks on images containing full spatial frequency information, we saw no representational differences. Overall, this integration of computational, neural, and behavioural findings shows the relevance of the exposure to and processing of input with a variation in spatial frequency content for some aspects of high-level object representations.

Spatial Frequency Thresholds for Detecting Latent Facial Signals of Threat

Perception ◽  
2019 ◽  
Vol 48 (3) ◽  
pp. 214-227
Author(s):  
Nicholas Watier ◽  
Brock DeGagne
Keyword(s):  
Spatial Frequency ◽  
Face Processing ◽  
Visual Information ◽  
Forced Choice ◽  
Face Identification ◽  
Staircase Procedure ◽  
Spatial Frequencies

This study examined whether latent facial signals of threat can be detected at more extreme ranges of spatial frequencies (SFs), and thus with fewer frequencies from an optimal middle band for face identification, compared with latent nonthreatening facial signals. Using an adaptive staircase procedure and a two-interval forced-choice same-different task, SF thresholds from the lower and higher ends of the SF spectrum were obtained for nonexpressive threatening and nonthreatening faces. Threatening faces were discriminated from neutral faces more quickly and accurately, and engendered more extreme SF thresholds, compared with nonthreatening faces. The results indicate that the components of latent threatening facial signals can be detected under a greater degree of impoverished visual information for face processing compared with their nonthreatening counterparts.

High Fundamental Spatial Frequencies and Edges have Different Perceptual Consequences in the ‘Group/End-to-End’ Movement Phenomenon

Perception ◽  
1981 ◽  
Vol 10 (4) ◽  
pp. 375-382 ◽  
Author(s):  
J Timothy Petersik ◽  
Jane Grassmuck
Keyword(s):  
Spatial Frequency ◽  
Interstimulus Interval ◽  
The Other ◽  
Square Wave ◽  
Temporal Parameters ◽  
Group Movement ◽  
Stimulus Waveform ◽  
Spatial Frequencies ◽  
End To End ◽  
Frame Duration

A subject viewing two alternating frames, each containing, say, three vertical stripes in a horizontal row, displaced laterally by one cycle in one frame with respect to the other, perceives either the three stripes moving left-right-left in unison (group movement) or one stripe moving from one end of the display to the other and the two overlapping stripes stationary (end-to-end movement). At suitable temporal parameters of presentation (frame duration, interstimulus interval) the perception of the display is bistable. Experiments have shown that the relative strengths of these alternative movement sensations depend upon the fundamental spatial frequency of the display and upon stimulus waveform. Square-wave stimuli, which have energy at high spatial frequencies, had effects opposite to those produced by increases in fundamental spatial frequency. Amblyopes differed from normal viewers only in the perception of the square-wave stimuli.

The Neural Substrates and Timing of Top–Down Processes during Coarse-to-Fine Categorization of Visual Scenes: A Combined fMRI and ERP Study

2010 ◽  
Vol 22 (12) ◽  
pp. 2768-2780 ◽  
Author(s):  
Carole Peyrin ◽  
Christoph M. Michel ◽  
Sophie Schwartz ◽  
Gregor Thut ◽  
Mohamed Seghier ◽  
...  
Keyword(s):  
Spatial Frequency ◽  
Visual Analysis ◽  
High Spatial Frequency ◽  
Neural Substrates ◽  
Brain Network ◽  
Processing Scheme ◽  
Spatial Frequencies ◽  
Visual Areas ◽  
Initial Activation ◽  
Coarse To Fine

Spatial frequencies in an image influence visual analysis across a distributed, hierarchically organized brain network. Low spatial frequency (LSF) information may rapidly reach high-order areas to allow an initial coarse parsing of the visual scene, which could then be “retroinjected” through feedback into lower level visual areas to guide finer analysis on the basis of high spatial frequency (HSF). To test this “coarse-to-fine” processing scheme and to identify its neural substrates in the human brain, we presented sequences of two spatial-frequency-filtered scenes in rapid succession (LSF followed by HSF or vice versa) during fMRI and ERPs in the same participants. We show that for low-to-high sequences (but not for high-to-low sequences), LSF produces a first increase of activity in prefrontal and temporo-parietal areas, followed by enhanced responses to HSF in primary visual cortex. This pattern is consistent with retroactive influences on low-level areas that process HSF after initial activation of higher order areas by LSF.

scholarly journals Sharpening coarse-to-fine stereo vision by perceptual learning: asymmetric transfer across the spatial frequency spectrum

2016 ◽  
Vol 3 (1) ◽  
pp. 150523 ◽  
Author(s):  
Roger W. Li ◽  
Truyet T. Tran ◽  
Ashley P. Craven ◽  
Tsz-Wing Leung ◽  
Sandy W. Chat ◽  
...  
Keyword(s):  
Spatial Frequency ◽  
Perceptual Learning ◽  
Frequency Spectrum ◽  
Three Dimensional ◽  
High Spatial Frequency ◽  
Visual Image ◽  
Spatial Frequencies ◽  
Early Visual Cortex ◽  
Coarse To Fine ◽  
Spatial Frequency Spectrum

Neurons in the early visual cortex are finely tuned to different low-level visual features, forming a multi-channel system analysing the visual image formed on the retina in a parallel manner. However, little is known about the potential ‘cross-talk’ among these channels. Here, we systematically investigated whether stereoacuity, over a large range of target spatial frequencies, can be enhanced by perceptual learning. Using narrow-band visual stimuli, we found that practice with coarse (low spatial frequency) targets substantially improves performance, and that the improvement spreads from coarse to fine (high spatial frequency) three-dimensional perception, generalizing broadly across untrained spatial frequencies and orientations. Notably, we observed an asymmetric transfer of learning across the spatial frequency spectrum. The bandwidth of transfer was broader when training was at a high spatial frequency than at a low spatial frequency. Stereoacuity training is most beneficial when trained with fine targets. This broad transfer of stereoacuity learning contrasts with the highly specific learning reported for other basic visual functions. We also revealed strategies to boost learning outcomes ‘beyond-the-plateau’. Our investigations contribute to understanding the functional properties of the network subserving stereovision. The ability to generalize may provide a key principle for restoring impaired binocular vision in clinical situations.

scholarly journals Monocular blur alters the tuning characteristics of stereopsis for spatial frequency and size

2016 ◽  
Vol 3 (9) ◽  
pp. 160273 ◽  
Author(s):  
Roger W. Li ◽  
Kayee So ◽  
Thomas H. Wu ◽  
Ashley P. Craven ◽  
Truyet T. Tran ◽  
...  
Keyword(s):  
Spatial Frequency ◽  
Narrow Band ◽  
Frequency Tuning ◽  
Low Frequency ◽  
High Spatial Frequency ◽  
Spatial Filters ◽  
Optimum Frequency ◽  
Spatial Frequencies ◽  
Coarse To Fine ◽  
Tuning Function

Our sense of depth perception is mediated by spatial filters at different scales in the visual brain; low spatial frequency channels provide the basis for coarse stereopsis, whereas high spatial frequency channels provide for fine stereopsis. It is well established that monocular blurring of vision results in decreased stereoacuity. However, previous studies have used tests that are broadband in their spatial frequency content. It is not yet entirely clear how the processing of stereopsis in different spatial frequency channels is altered in response to binocular input imbalance. Here, we applied a new stereoacuity test based on narrow-band Gabor stimuli. By manipulating the carrier spatial frequency, we were able to reveal the spatial frequency tuning of stereopsis, spanning from coarse to fine, under blurred conditions. Our findings show that increasing monocular blur elevates stereoacuity thresholds ‘selectively’ at high spatial frequencies, gradually shifting the optimum frequency to lower spatial frequencies. Surprisingly, stereopsis for low frequency targets was only mildly affected even with an acuity difference of eight lines on a standard letter chart. Furthermore, we examined the effect of monocular blur on the size tuning function of stereopsis. The clinical implications of these findings are discussed.

scholarly journals SPPD: A Novel Reassembly Method for 3D Terracotta Warrior Fragments Based on Fracture Surface Information

2021 ◽  
Vol 10 (8) ◽  
pp. 525
Author(s):  
Wenmin Yao ◽  
Tong Chu ◽  
Wenlong Tang ◽  
Jingyu Wang ◽  
Xin Cao ◽  
...  
Keyword(s):  
Fracture Surface ◽  
Principal Component ◽  
Point Clouds ◽  
Three Dimension ◽  
Registration Method ◽  
Series Of Experiments ◽  
Coarse To Fine ◽  
Fine Registration ◽  
Common Situation ◽  
Better Than

As one of China′s most precious cultural relics, the excavation and protection of the Terracotta Warriors pose significant challenges to archaeologists. A fairly common situation in the excavation is that the Terracotta Warriors are mostly found in the form of fragments, and manual reassembly among numerous fragments is laborious and time-consuming. This work presents a fracture-surface-based reassembling method, which is composed of SiamesePointNet, principal component analysis (PCA), and deep closest point (DCP), and is named SPPD. Firstly, SiamesePointNet is proposed to determine whether a pair of point clouds of 3D Terracotta Warrior fragments can be reassembled. Then, a coarse-to-fine registration method based on PCA and DCP is proposed to register the two fragments into a reassembled one. The above two steps iterate until the termination condition is met. A series of experiments on real-world examples are conducted, and the results demonstrate that the proposed method performs better than the conventional reassembling methods. We hope this work can provide a valuable tool for the virtual restoration of three-dimension cultural heritage artifacts.

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