Selective Attention to Specific Location Cues: The Peak and Center of a Patch are Equally Accessible as Location Cues

Perception ◽  
1998 ◽  
Vol 27 (9) ◽  
pp. 1015-1023 ◽  
Author(s):  
Hiromi Akutsu ◽  
Dennis M Levi
Keyword(s):  
Visual System ◽  
Spatial Localization ◽  
Second Derivative ◽  
Specific Location ◽  
Zero Crossings ◽  
Luminance Distribution ◽  
Luminance Profile ◽  
Asymmetric Pattern ◽  
Visible Area ◽  
At Will

Asymmetric patterns have several spatially distinct cues for spatial localization. These cues include the peak of the luminance distribution, the centroid of the contrast distribution, zero-crossings in the second derivative of the luminance profile, and the midpoint of the visible area. If these cues are represented as primitives in the visual system, the observer should be able to access them at will. To examine whether observers can selectively attend to particular cues, we measured perceived alignment for an asymmetric pattern with two distinct instructions: “align the peak”, and “align the center”. We found that observers could align the patterns in accord with the instructions with identical precision, suggesting that the peak and the center cues were equally accessible by the observer. We conclude that multiple localization cues are represented in and can be selectively accessed by the visual system.

Coordinating movement at two joints: a principle of linear covariance

1996 ◽  
Vol 75 (4) ◽  
pp. 1760-1764 ◽  
Author(s):  
G. L. Gottlieb ◽  
Q. Song ◽  
D. A. Hong ◽  
G. L. Almeida ◽  
D. Corcos
Keyword(s):  
Degrees Of Freedom ◽  
Sagittal Plane ◽  
Linear Scaling ◽  
Joint Movement ◽  
Zero Crossings ◽  
Linear Dynamic ◽  
Important Principle ◽  
Linear Covariance ◽  
At Will ◽  
Scaling Rule

1. Six subjects performed fast, "single-joint" flexions at either the elbow or shoulder over three angular distances in a sagittal plane. Movement endpoints were located to require flexion of only a single, "focal" joint, without any external, mechanical constraint on the other, "nonfocal" joint. Three subjects performed another series of movements between two targets while moving along different paths and in which both joints were flexed. 2. We compared the torque patterns that were produced at the two joints. For single-joint movements, they were both biphasic pulses that accelerated and then decelerated the limb. 3. The torque at the nonfocal joint of a single joint movement was very close to linearly proportional to that at the focal joint throughout the movement. Elbow and shoulder torques differed by a linear scaling constant and went through extrema and zero crossings almost simultaneously. 4. In contrast, during movements in which subjects were explicitly instructed to use a hand path they would not naturally, use the linear interjoint torque scaling rule did not apply. This demonstrated that when we wish to move along a path between two targets that is not produced by linear torque covariation, we are able to modify that rule at will. 5. We speculate that linear, dynamic covariation of the torque patterns across two joints may be an important principle for reducing the number of degrees of freedom that the nervous system must independently control in performing unconstrained limb movements over naturally chosen paths.

Second Derivative Tunable Diode Laser Spectrometry for Line Profile Determination. II. Experimental Results

1980 ◽  
Vol 34 (1) ◽  
pp. 56-60 ◽  
Author(s):  
David L. Grieble ◽  
Mark L. Olson ◽  
Jeffrey N-P. Sun ◽  
Peter R. Griffiths
Keyword(s):  
Diode Laser ◽  
Half Width ◽  
Tunable Diode Laser ◽  
Second Derivative ◽  
Single Beam ◽  
Zero Crossings ◽  
Diode Laser Spectrometer ◽  
Laser Spectrometry ◽  
Second Derivative Spectra ◽  
Two Parameters

The effect of the amplitude of the current modulation on experimental second derivative spectra measured using a tunable diode laser spectrometer is discussed. Spectra with adequate signal/noise ratios can only be measured when the amplitude of the modulation is about equal to the half width at half height. Two parameters, the distance between the zero crossings and the ratio of the minimal and maximal excursions, may be fit to an empirical hypersurface to obtain values for the peak absorbance, the actual half width and the collision-broadened half width. Although the peak absorbance is not accurately calculated, the line widths appear to be calculated to at least the same accuracy that can be obtained from the single-beam absorption spectrum.

Effect of Spatial Structure Defined by Binocular Disparity with Uniform Luminance on Lightness

Perception ◽  
2019 ◽  
Vol 49 (1) ◽  
pp. 3-20
Author(s):  
Kei Kanari ◽  
Hirohiko Kaneko
Keyword(s):  
Spatial Structure ◽  
Visual System ◽  
Uniform Distribution ◽  
Binocular Disparity ◽  
Stimulus Space ◽  
Luminance Distribution ◽  
Scene Structure ◽  
Structure Relation ◽  
Random Dot Stereogram ◽  
The Relationship

We examined whether lightness is determined based on the experience of the relationship between a scene’s illumination and its spatial structure in actual environments. For this purpose, we measured some characteristics of scene structure and the illuminance in actual scenes and found some correlations between them. In the psychophysical experiments, a random-dot stereogram consisting of dots with uniform distribution was used to eliminate the effects of local luminance and texture contrasts. Participants matched the lightness of a presented target patch in the stimulus space to that of a comparison patch by adjusting the latter’s luminance. Results showed that the matched luminance tended to increase when the target patch was interpreted as receiving weak illumination in some conditions. These results suggest that the visual system can probably infer a scene’s illumination from a spatial structure without luminance distribution information under an illumination–spatial structure relation.

Performance Optimization of DWT-Based Image Watermarking Using Genetic Algorithms

2009 ◽  
pp. 210-221
Author(s):  
Ali Al-Haj ◽  
Aymen Abu-Errub
Keyword(s):  
Genetic Algorithms ◽  
Visual System ◽  
Human Visual System ◽  
Performance Optimization ◽  
Image Watermarking ◽  
Spatial Localization ◽  
Theoretical Models ◽  
Experimental Results ◽  
Wavelets Transform ◽  
Discrete Wavelets

The excellent spatial localization, frequency spread, and multi-resolution characteristics of the discrete wavelets transform (DWT), which are similar to the theoretical models of the human visual system, facilitated the development of many imperceptible and robust DWT-based watermarking algorithms. However, there has been extremely few proposed algorithms on optimized DWT-based image watermarking that can simultaneously provide perceptual transparency and robustness Since these two watermarking requirements are conflicting, in this paper we treat the DWT-based image watermarking problem as an optimization problem, and solve it using genetic algorithms. We demonstrate through the experimental results we obtained that optimal DWT-based image watermarking can be achieved only if watermarking has been applied at specific wavelet sub-bands and by using specific watermarkamplification values.

Topological disorder in peripheral vision

1994 ◽  
Vol 11 (5) ◽  
pp. 1033-1036 ◽  
Author(s):  
Robert F. Hess ◽  
Jim McCarthy
Keyword(s):  
Object Recognition ◽  
Visual Field ◽  
Visual System ◽  
Peripheral Vision ◽  
Spatial Localization ◽  
Spatial Uncertainty ◽  
Good Sensitivity ◽  
Simple Consequence ◽  
Topological Disorder

AbstractOne of the most striking properties of the mammalian visual system is that it is only the central part of the visual field, the fovea, where vision is most acute. The superiority of the fovea is particularly evident in tasks requiring accurate spatial localization. It is currently thought that peripheral spatial uncertainty is a simple consequence of the decreased sampling grain of the peripheral field. We show that the topological fidelity of the afferent projection declines with eccentricity away from the fovea and that it is this rather than the sampling grain that underlies the poorer performance of the periphery in tasks involving spatial localization. The combination of normal sampling and a disordered topology results in the periphery having good sensitivity for detection but poor sensitivity for object recognition.

scholarly journals Variations in crowding, saccadic precision, and spatial localization reveal the shared topology of spatial vision

2017 ◽  
Vol 114 (17) ◽  
pp. E3573-E3582 ◽  
Author(s):  
John A. Greenwood ◽  
Martin Szinte ◽  
Bilge Sayim ◽  
Patrick Cavanagh
Keyword(s):  
Visual Field ◽  
Visual System ◽  
Spatial Vision ◽  
Saccadic Eye Movements ◽  
Spatial Localization ◽  
Visual Sensitivity ◽  
Hierarchical Regression ◽  
Common Source ◽  
Lower Visual Field ◽  
Two Measures

Visual sensitivity varies across the visual field in several characteristic ways. For example, sensitivity declines sharply in peripheral (vs. foveal) vision and is typically worse in the upper (vs. lower) visual field. These variations can affect processes ranging from acuity and crowding (the deleterious effect of clutter on object recognition) to the precision of saccadic eye movements. Here we examine whether these variations can be attributed to a common source within the visual system. We first compared the size of crowding zones with the precision of saccades using an oriented clock target and two adjacent flanker elements. We report that both saccade precision and crowded-target reports vary idiosyncratically across the visual field with a strong correlation across tasks for all participants. Nevertheless, both group-level and trial-by-trial analyses reveal dissociations that exclude a common representation for the two processes. We therefore compared crowding with two measures of spatial localization: Landolt-C gap resolution and three-dot bisection. Here we observe similar idiosyncratic variations with strong interparticipant correlations across tasks despite considerably finer precision. Hierarchical regression analyses further show that variations in spatial precision account for much of the variation in crowding, including the correlation between crowding and saccades. Altogether, we demonstrate that crowding, spatial localization, and saccadic precision show clear dissociations, indicative of independent spatial representations, whilst nonetheless sharing idiosyncratic variations in spatial topology. We propose that these topological idiosyncrasies are established early in the visual system and inherited throughout later stages to affect a range of higher-level representations.

Author response for "The brain of the African wild dog. IV . The visual system"

2020 ◽  
Author(s):  
Samson Chengetanai ◽  
Adhil Bhagwandin ◽  
Mads F. Bertelsen ◽  
Therese Hård ◽  
Patrick R. Hof ◽  
...  
Keyword(s):  
Visual System ◽  
Author Response ◽  
African Wild Dog ◽  
Wild Dog ◽  
The Brain

Microbulldozing and Microchiseling

1969 ◽  
Vol 27 ◽  
pp. 134-135
Author(s):  
J.N. Ramsey ◽  
D.P. Cameron ◽  
F.W. Schneider
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Material Handling ◽  
Microprobe Analysis ◽  
Foreign Matter ◽  
Specific Location ◽  
Potential Problems ◽  
Knoop Indenter ◽  
Scanning Electron ◽  
Microhardness Tester

As computer components become smaller the analytical methods used to examine them and the material handling techniques must become more sensitive, and more sophisticated. We have used microbulldozing and microchiseling in conjunction with scanning electron microscopy, replica electron microscopy, and microprobe analysis for studying actual and potential problems with developmental and pilot line devices. Foreign matter, corrosion, etc, in specific locations are mechanically loosened from their substrates and removed by “extraction replication,” and examined in the appropriate instrument. The mechanical loosening is done in a controlled manner by using a microhardness tester—we use the attachment designed for our Reichert metallograph. The working tool is a pyramid shaped diamond (a Knoop indenter) which can be pushed into the specimen with a controlled pressure and in a specific location.

Use of the Magnetostatic Analogue In Electromagnetic Lens Engineering

1970 ◽  
Vol 28 ◽  
pp. 360-361
Author(s):  
John W. Coleman
Keyword(s):  
Boundary Conditions ◽  
High Performance ◽  
Force Fields ◽  
Optical Design ◽  
Direct Conversion ◽  
Design Engineering ◽  
Design Data ◽  
Scalar Potentials ◽  
Geometric Elements ◽  
At Will

In the design engineering of high performance electromagnetic lenses, the direct conversion of electron optical design data into drawings for reliable hardware is oftentimes difficult, especially in terms of how to mount parts to each other, how to tolerance dimensions, and how to specify finishes. An answer to this is in the use of magnetostatic analytics, corresponding to boundary conditions for the optical design. With such models, the magnetostatic force on a test pole along the axis may be examined, and in this way one may obtain priority listings for holding dimensions, relieving stresses, etc..The development of magnetostatic models most easily proceeds from the derivation of scalar potentials of separate geometric elements. These potentials can then be conbined at will because of the superposition characteristic of conservative force fields.

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