Are Curves Detected by ‘Curvature Detectors’?

Perception ◽  
1978 ◽  
Vol 7 (1) ◽  
pp. 51-64 ◽  
Author(s):  
Brian N Timney ◽  
Colin Macdonald
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Human Vision ◽  
Orientation Tuning ◽  
Threshold Elevation ◽  
Maximum Value ◽  
Adaptation Experiment ◽  
The Relationship

Five experiments which attempted to evaluate the relationship between orientation and curvature selectivity in human vision are described. In the first two experiments, threshold elevation for curved gratings was measured after exposure to similar gratings, with the use of either an adaptation (experiment 1) or a masking (experiment 2) paradigm. In both experiments threshold elevation occurred which was selective for both the degree and the direction of curvature of the adapting pattern. Experiment 3 compared the effects of adapting to tilted rectilinear or vertical curved gratings upon threshold for a vertical rectilinear grating. Threshold elevation declined systematically as the adapting gratings were either tilted or made more curved. Experiment 4 measured curvature selectivity as a function of the orientation of a curved adapting grating. Threshold elevation declined as the adapting grating was tilted more, but curvature selectivity remained. Experiment 5 measured the orientation tuning for curved gratings directly. Threshold elevation declined to 50% of its maximum value at an adapting orientation of about 28°. This was constant for all values of curvature used. The results are discussed with reference to the question of whether the human visual system contains ‘curvature detectors’ or linear-contour detectors which respond to the tangents of curves.

The Study of Spatial Frequency Channels for Human Visual System

2019 ◽  
Vol 33 (06) ◽  
pp. 1955007
Author(s):  
Xiangyang Xu ◽  
Qiao Chen ◽  
Ruixin Xu
Keyword(s):  
Receptive Field ◽  
Spatial Frequency ◽  
Visual System ◽  
Human Visual System ◽  
Frequency Tuning ◽  
Tuning Curve ◽  
Vision System ◽  
Human Vision ◽  
Psychophysical Experiment ◽  
Human Vision System

Similar to auditory perception of sound system, color perception of the human visual system also presents a multi-frequency channel property. In order to study the multi-frequency channel mechanism of how the human visual system processes color information, the paper proposed a psychophysical experiment to measure the contrast sensitivities based on 17 color samples of 16 spatial frequencies on CIELAB opponent color space. Correlation analysis was carried out on the psychophysical experiment data, and the results show obvious linear correlations of observations for different spatial frequencies of different observers, which indicates that a linear model can be used to model how human visual system processes spatial frequency information. The results of solving the model based on the experiment data of color samples show that 9 spatial frequency tuning curves can exist in human visual system with each lightness, R–G and Y–B color channel and each channel can be represented by 3 tuning curves, which reflect the “center-around” form of the human visual receptive field. It is concluded that there are 9 spatial frequency channels in human vision system. The low frequency tuning curve of a narrow-frequency bandwidth shows the characteristics of lower level receptive field for human vision system, the medium frequency tuning curve shows a low pass property of the change of medium frequent colors and the high frequency tuning curve of a width-frequency bandwidth, which has a feedback effect on the low and medium frequency channels and shows the characteristics of higher level receptive field for human vision system, which represents the discrimination of details.

The Site of Binocular Rivalry Suppression

Perception ◽  
1979 ◽  
Vol 8 (2) ◽  
pp. 143-152 ◽  
Author(s):  
Randolph Blake ◽  
Randall Overton
Keyword(s):  
Visual System ◽  
Binocular Rivalry ◽  
Human Visual System ◽  
Striate Cortex ◽  
High Contrast ◽  
Threshold Elevation ◽  
Short Term ◽  
Contrast Adaptation ◽  
A Site ◽  
Lines Of Evidence

Two experiments were performed to localize the site of binocular rivalry suppression in relation to the locus of grating adaptation. In one experiment it was found that phenomenal suppression of a high-contrast adaptation grating presented to one eye had no influence on the strength of the threshold-elevation aftereffect measured interocularly. Evidently information about the adaptation grating arrives at the site of the aftereffect (presumably binocular neurons) even during suppression. In a second experiment 60 s of grating adaptation was found to produce a short-term reduction in the predominance of the adapted eye during binocular rivalry. These findings provide converging lines of evidence that suppression occurs at a site in the human visual system after the locus of grating adaptation and, hence, after the striate cortex.

Orientation Specificity and Spatial Selectivity in Human Vision

Perception ◽  
1973 ◽  
Vol 2 (1) ◽  
pp. 53-60 ◽  
Author(s):  
J A Movshon ◽  
C Blakemore
Keyword(s):  
Spatial Frequency ◽  
Human Visual System ◽  
Human Vision ◽  
Orientation Tuning ◽  
High Contrast ◽  
Vertical Grating ◽  
Spatial Frequencies ◽  
High Contrast Grating ◽  
Orientation Specificity ◽  
Adaptation Method

An adaptation method is used to determine the orientation specificity of channels sensitive to different spatial frequencies in the human visual system. Comparison between different frequencies is made possible by a data transformation in which orientational effects are expressed in terms of equivalent contrast (the contrast of a vertical grating producing the same adaptational effect as a high-contrast grating of a given orientation). It is shown that, despite great variances in the range of orientations affected by adaptation at different spatial frequencies (±10° to ±50°), the half-width at half-amplitude of the orientation channels does not vary systematically as a function of spatial frequency over the range tested (2·5 to 20 cycles deg−1). Two subjects were used and they showed significantly different orientation tuning across the range of spatial frequencies. The results are discussed with reference to previous determinations of orientation specificity, and to related psychophysical and neurophysiological phenomena.

scholarly journals Exploiting ambiguity: The diffraction artefact and the architectural surface

2019 ◽  
Vol 17 (1) ◽  
pp. 103-115
Author(s):  
Linda Matthews ◽  
Gavin Perin
Keyword(s):  
Visual System ◽  
Urban Space ◽  
Digital Imaging ◽  
Human Visual System ◽  
Human Vision ◽  
System Model ◽  
The Political ◽  
Transmission Pipeline ◽  
Image Production ◽  
Vantage Points

In the contemporary ‘envisioned’ environment, Internet webcams, low- and high-altitude unmanned aerial vehicles and satellites are the new vantage points from which to construct the image of the city. Armed with hi-resolution digital optical technologies, these vantage points effectively constitute a ubiquitous visioning apparatus serving either the politics of promotion or surveillance. Given the political dimensions of this apparatus, it is important to note that this digital imaging of public urban space refers to the human visual system model. In order to mimic human vision, a set of algorithm patterns are used to direct numerous ‘soft’ and ‘hard’ technologies. Mimicry thus has a cost because this insistence on the human visual system model necessitates multiple transformative moments in the production and transmission pipeline. If each transformative moment opens a potential vulnerability within the visioning apparatus, then every glitch testifies to the artificiality of the image. Moreover, every glitch potentially interrupts the political narratives be communicated in contemporary image production and transmission. Paradoxically, the current use of scripting to create glitch-like images has reimagined glitches as a discrete aesthetic category. This article counters this aestheticisation by asserting glitching as a disruption in communication. The argument will rely on scaled tests produced by one of the authors who show how duplicating the digital algorithmic patterns used within the digital imaging pipeline on any exterior building surface glitches the visual data captured within that image. Referencing image-based techniques drawn from the Baroque and contemporary modes of camouflage, it will be argued that the visual aberrations created by these algorithm-based patterned facades can modify strategically the ‘emission signature’ of selected parts of the urban fabric. In this way, the glitch becomes a way to intercede in the digital portrayal of city.

Relationships between Channels for Colour and Spatial Frequency in Human Vision

Perception ◽  
1973 ◽  
Vol 2 (1) ◽  
pp. 31-40 ◽  
Author(s):  
V Virsu ◽  
S Haapasalo
Keyword(s):  
Spatial Frequency ◽  
Visual System ◽  
Human Visual System ◽  
Human Vision ◽  
Visual Objects ◽  
The Third ◽  
Simultaneous Integration ◽  
Two Systems ◽  
Channel Systems

Five forms of relationships and four types of channels are possible between two systems of sensory channels. The relationships between channels for colour and spatial frequency were studied in three adaptation experiments. In the first, a new colour-specific spatial aftereffect was found, which indicates the existence of channels that are specific both to colour and to spatial frequency. The second showed that the spatial-frequency aftereffect of Blakemore and Sutton is not colour specific, which indicates that there are channels for spatial frequency that are not colour specific. The third demonstrated that coloured afterimages are not spatial-frequency specific immediately after adaptation, although they become so later. This indicates that there are channels for colour that are not spatial-frequency specific. The existence of these three types of channels implies that the channel systems for colour and spatial frequency overlap partially and mutually in the human visual system. This kind of organisation of channel systems, if it exists, may form the psychophysical structure that is required for the capacity of simultaneous integration and differentiation in the perception of colour and size of visual objects.

Symbolic Pointillism: Computer Art Motivated by Human Brain Structures

Leonardo ◽  
2005 ◽  
Vol 38 (4) ◽  
pp. 337-340 ◽  
Author(s):  
Norbert Krüger ◽  
Florentin Wörgötter
Keyword(s):  
Visual System ◽  
Human Brain ◽  
Human Visual System ◽  
Vision System ◽  
Visual Representations ◽  
Brain Structures ◽  
Human Vision ◽  
Artificial Vision ◽  
Computer Art ◽  
Functional Aspects

The authors introduce a new kind of computer art motivated by cortical structures in the human visual system. This type of computer art is related to the sub-group of the impressionist art movement called pointillism. However, while pointillism visualizes and makes use of processes that have been associated with the human eye, Symbolic Pointillism also makes cortical processes explicit. The visual representations underlying this art have been developed during a project that aims at the transfer of functional aspects of human vision to artificial systems. The authors have applied their findings in such an artificial vision system and in a sound/vision installation.

scholarly journals Wholes and subparts in visual processing of human agency

2008 ◽  
Vol 276 (1658) ◽  
pp. 861-869 ◽  
Author(s):  
Peter Neri
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Visual Processing ◽  
Conclusive Evidence ◽  
Stage Model ◽  
Local Motion ◽  
Top Down ◽  
Two Stage ◽  
One Stage ◽  
The Relationship

The human visual system is remarkably sensitive to stimuli conveying actions, for example the fighting action between two agents. A central unresolved question is whether each agent is processed as a whole in one stage, or as subparts (e.g. limbs) that are assembled into an agent at a later stage. We measured the perceptual impact of perturbing an agent either by scrambling individual limbs while leaving the relationship between limbs unaffected or conversely by scrambling the relationship between limbs while leaving individual limbs unaffected. Our measurements differed for the two conditions, providing conclusive evidence against a one-stage model. The results were instead consistent with a two-stage processing pathway: an early bottom-up stage where local motion signals are integrated to reconstruct individual limbs (arms and legs), and a subsequent top-down stage where limbs are combined to represent whole agents.

Parts of visual shape as primitives for categorization

1998 ◽  
Vol 21 (1) ◽  
pp. 36-37 ◽  
Author(s):  
Manish Singh ◽  
Barbara Landau
Keyword(s):  
Object Recognition ◽  
Visual System ◽  
Recent Work ◽  
Human Visual System ◽  
Human Vision ◽  
Visual Shape

Converging psychophysical evidence suggests that the human visual system parses shapes into component parts for the purposes of object recognition. We examine the Schyns et al. claim of “creation” of features in light of recent work on part-based representations of visual shape, particularly the perceptual rules that human vision uses to parse shapes.

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