Illusory Contours Do Not Capture Stereopsis—They Just Constrain the Depth Spreading

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 182-182
Author(s):  
J Häkkinen ◽  
I Kojo ◽  
M Liinasuo ◽  
G Nyman
Keyword(s):  
Central Area ◽  
Stereoscopic Depth ◽  
Illusory Figure ◽  
Illusory Contours ◽  
Background Texture ◽  
Background Pattern

If vertical cut-out sectors defining a Kanizsa square are given crossed disparity, the illusory figure appears in depth. Such an illusory figure can pull the background pattern inside the illusory figure to the same depth. It has been assumed that illusory contours are necessary for this phenomenon, which is called stereo capture (Ramachandran, 1986 Perception & Psychophysics39 361 – 373). However, we noticed that the vertical cut-out sectors of the inducing figures (‘pacmen’) are not the only structures that can capture the background texture. The rows of background dots that are enclosed between the disparate vertical cut-out sectors also have unambiguous stereoscopic depth. Thus it might be possible that the disparate rows alone capture the background texture. To investigate our hypothesis we created a stereogram in which the inducing figures were removed. It consisted of a dotted background texture and four areas devoid of dots. The dotless areas corresponded to the areas which were occluded by the original inducing figures. Because of this, the top and bottom rows inside the central area were in crossed disparity. According to our results (a) depth capture also occurred without illusory contours; (b) when illusory contours were not present, the depth of the disparate rows spread more often to other areas. Usually the depth spread first to the central area of the figure and after that horizontally to other areas of the figure. Therefore, we conclude that illusory contours do not capture stereopsis—they just constrain the depth spreading.

Illusory Contours from Pictorially Three-Dimensional Inducing Elements: Counterevidence for Parks and Rock's Example

Perception ◽  
1993 ◽  
Vol 22 (7) ◽  
pp. 809-818 ◽  
Author(s):  
Franco Purghé
Keyword(s):  
Three Dimensional ◽  
Illusory Figure ◽  
Illusory Contours ◽  
Line Elements

In 1990 Parks and Rock claimed that, in pictorially three-dimensional (3-D) inducing patterns, an illusory figure does not emerge if a clear occlusion event is not present. A new pictorially 3-D pattern is presented which contradicts this claim. Two experiments were carried out. The first was aimed at ascertaining the presence of an illusory figure in the new 3-D pattern; the second was aimed at offering evidence that in Parks and Rock's pattern the disappearance of the illusory figure could be due to local interferences caused by the line elements in contact with the inducing borders. The results tend to contradict Parks and Rock's conclusions.

On the Microgenesis of Illusory Figures: A Failure to Replicate

Perception ◽  
1994 ◽  
Vol 23 (7) ◽  
pp. 857-862 ◽  
Author(s):  
Theodore E Parks
Keyword(s):  
Problem Solving ◽  
Viewing Time ◽  
Illusory Figure ◽  
Illusory Contours ◽  
Do So

Reynolds found in 1981 that with increased viewing time of a pattern which may or may not produce illusory contours there were: first, reports of the pattern without an illusory figure; then, at longer exposures, an increase in the frequency with which illusory figures were reported; and then, with still longer exposures, a decrease in such reports if the pattern contained elements which tended to contradict the possibility of such a figure. Unfortunately, however, three attempts to replicate these potentially very important findings—with the aid of substantially improved methodology—consistently failed to do so. It is suggested that this failure, although it is disappointing to those who subscribe to a ‘problem solving’ explanation of illusory contours, may not constitute a strong refutation of such a theory. Regardless, the purpose in the report is to clarify and rectify the published record concerning this part of the evidential underpinnings of that theory.

Amodal Completion versus Induced Inhomogeneities in the Organization of Illusory Figures

Perception ◽  
1992 ◽  
Vol 21 (5) ◽  
pp. 627-636 ◽  
Author(s):  
Marco Davi ◽  
Baingio Pinna ◽  
Marco Sambin
Keyword(s):  
Phenomenological Model ◽  
Control Experiment ◽  
Amodal Completion ◽  
Brightness Contrast ◽  
Primary Factor ◽  
Paired Comparisons ◽  
Illusory Figure ◽  
Illusory Contours ◽  
Energetic Model ◽  
Method Of Paired Comparisons

An analysis is presented of a phenomenological model of illusory contours. The model is based on amodal completion as the primary factor giving rise to the illusory figure. In the experiment, conducted by the method of paired comparisons, the same parameter was manipulated in two series of equivalent configurations. The first series yielded examples of amodal completion, the second examples of illusory figures. Three groups of subjects evaluated the magnitude of completion, the brightness contrast of the illusory figure, and the contour clarity of the illusory figure. A control experiment was conducted, which demonstrated that in these configurations amodal completion and amodal continuation behave in the same way. Line displacement did not influence the brightness or the contour clarity of the illusory figures, though it influenced the magnitude of amodal completion. These results are in agreement with the energetic model developed by Sambin.

Banishing Illusory Contours: A New Possibility

Perception ◽  
1997 ◽  
Vol 26 (6) ◽  
pp. 753-754 ◽  
Author(s):  
Theodore E Parks
Keyword(s):  
Harmful Effect ◽  
Illusory Figure ◽  
Illusory Contours

As an alternative to an earlier hypothesis, it may be that the harmful effect of certain modifications to a pattern which would otherwise produce an illusory figure may be due to excessive coincidences that would be present if an illusory figure were to be seen.

Young Infants' Perception of Illusory Contours in Dynamic Displays

Perception ◽  
1998 ◽  
Vol 27 (3) ◽  
pp. 341-353 ◽  
Author(s):  
Scott P Johnson ◽  
Richard N Aslin
Keyword(s):  
Surface Texture ◽  
Illusory Contours ◽  
The Third ◽  
Young Infants ◽  
Background Texture ◽  
Spatiotemporal Integration

Ninety-six 4-month-old infants were habituated to one of three computer-generated displays depicting two rod parts above and below an occluding box. In the first display, the surfaces and boundaries of the rod and box were specified by dense surface texture. Their depth segregation was specified by accretion and deletion of background texture and motion shear. In the second display, the unity of the rod parts and box, and their depth segregation, were specified only by illusory contours. In the third display, the boundaries of the rod and box were specified by illusory contours, perceptible only via spatiotemporal integration of accretion and deletion of sparse-background-texture elements. Infants appeared to perceive object unity, and segregate the rod and box surfaces, in all three displays, indicating use of illusory contours to perceive bounded surfaces in depth. The results suggest a cognitive contribution to perception of some illusory contours, abilities which seem to be present by at least 4 months of age.

Is Stereoscopic Capture Possible with Three-Dimensionally Slanted or Curved Illusory Surfaces?

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 73-73
Author(s):  
J Häkkinen ◽  
M Liinasuo ◽  
I Kojo ◽  
G Nyman
Keyword(s):  
Three Dimensional ◽  
Complex Surface ◽  
Dimensional Structure ◽  
Curved Surfaces ◽  
Surface Form ◽  
Complex Surfaces ◽  
Illusory Contours ◽  
Three Dimensional Structure ◽  
Background Texture ◽  
Constant Period

The depth of disparate illusory contours affects the perception of background patterns that are enclosed by these contours. If the pattern is repetitive, the depth of the illusory surface is attributed to texture elements even though the texture is in zero disparity. Previous results have suggested that this phenomenon, called stereoscopic capture, is possible only with frontoparallel surfaces (Ramachandran, 1986 Perception & Psychophysics39 361 – 373). We hypothesised that the disruption of stereo capture with three-dimensionally slanted or curved surfaces has been due to the impossibility of consistent rematching of background texture elements. If the texture is designed in such a way that adjacent elements can be rematched to form a surface that is consistent with the three-dimensional structure of the illusory surface, the capture should be possible with complex surfaces. We investigated our hypothesis by showing three-dimensionally slanted and curved surfaces to subjects and changing the pattern of the background texture. According to our results a texture of a constant period can be captured only by a frontoparallel surface; however, if the texture is designed to be consistent with the three-dimensional structure of the complex surface, the texture elements that initially form a frontoparallel surface form a complex surface when they are captured. We conclude that (a) stereoscopic capture is possible with complex three-dimensional surfaces; (b) the possible discrete matches within the background texture determine the possible three-dimensional forms that can be captured and therefore stereoscopic capture should not be characterised only as depth interpolation (Mitchison and McKee, 1987 Vision Research27 285 – 294) between large image elements.

Classifying Illusory Contours: Edges Defined by “Pacman” and Monocular Tokens

1997 ◽  
Vol 77 (2) ◽  
pp. 731-736 ◽  
Author(s):  
Gerald Westheimer ◽  
Wu Li
Keyword(s):  
Stereoscopic Depth ◽  
Orientation Discrimination ◽  
Knife Edge ◽  
Illusory Contours ◽  
Edge Orientation ◽  
Tilt Illusion ◽  
Orientation Contrast ◽  
Supporting Structures ◽  
Better Than

Westheimer, Gerald and Wu Li. Classifying illusory contours: edges defined by “pacman” and monocular tokens. J. Neurophysiol. 77: 731–736, 1997. Thresholds for the discrimination of orientation were measured in the human fovea for figures and borders delineated by solid lines and by “pacman” tokens as introduced by Kanizsa, as well as by contours induced by monocular tokens giving a stereoscopic depth illusion of a knife edge. Orientation discrimination of these illusory contours is poorer by a factor of ∼2 than that of equivalent contours made of solid lines and is not much better than that for their supporting structures if taken alone. It is concluded that these kinds of illusory borders do not address the “border” or “edge” mechanism in the same way as real lines. Orientation discrimination and simultaneous orientation contrast (tilt illusion) were compared for a variety of illusory borders. The more robust the borders, i.e., the more sensitive to changes in orientation, the less their susceptibility to the tilt illusion.

The crystallography characteristic of (Mn,Fe)S single crystal

1990 ◽  
Vol 48 (4) ◽  
pp. 898-899
Author(s):  
Jiang Xishan
Keyword(s):  
Single Crystal ◽  
Cast Steel ◽  
Point Group ◽  
Central Area ◽  
Hexagonal Crystal ◽  
Growth Step ◽  
Left And Right ◽  
Relationship Of ◽  
Fcc Structure ◽  
New Discovery

This paper reports the growth step pattern and morphology at equilibrium and growth states of (Mn,Fe)S single crystal on the wall of micro-voids in ZG25 cast steel by using scanning electron microscope. Seldom report was presented on the growth morphology and steppattern of (Mn,Fe)S single crystal.Fig.1 shows the front half of the polyhedron of(Mn,Fe)S single crystal,its central area being the square crystal plane,the two pairs of hexagons symmetrically located in the high and low, the left and right with a certain, angle to the square crystal plane.According to the symmetrical relationship of crystal, it was defined that the (Mn,Fe)S single crystal at equilibrium state is tetrakaidecahedron consisted of eight hexagonal crystal planes and six square crystal planes. The macroscopic symmetry elements of the tetrakaidecahedron correpond to Oh—n3m symmetry class of fcc structure,in which the hexagonal crystal planes are the { 111 } crystal planes group,square crystal plaits are the { 100 } crystal planes group. This new discovery of the (Mn,Fe)S single crystal provides a typical example of the point group of Oh—n3m.

Chronic immobilization stress induces anxiety-related behaviors and affects brain essential minerals in male rats

2020 ◽  
pp. 1-8
Author(s):  
Zafer Sahin ◽  
Alpaslan Ozkurkculer ◽  
Omer Faruk Kalkan ◽  
Ahmet Ozkaya ◽  
Aynur Koc ◽  
...  
Keyword(s):  
Immobilization Stress ◽  
Central Area ◽  
Essential Elements ◽  
Male Rats ◽  
Control Group ◽  
Male Wistar Rats ◽  
Swimming Test ◽  
The Brain ◽  
Center Area ◽  
Chronic Immobilization Stress

Abstract. Alterations of essential elements in the brain are associated with the pathophysiology of many neuropsychiatric disorders. It is known that chronic/overwhelming stress may cause some anxiety and/or depression. We aimed to investigate the effects of two different chronic immobilization stress protocols on anxiety-related behaviors and brain minerals. Adult male Wistar rats were divided into 3 groups as follows ( n = 10/group): control, immobilization stress-1 (45 minutes daily for 7-day) and immobilization stress-2 (45 minutes twice a day for 7-day). Stress-related behaviors were evaluated by open field test and forced swimming test. In the immobilization stress-1 and immobilization stress-2 groups, percentage of time spent in the central area (6.38 ± 0.41% and 6.28 ± 1.03% respectively, p < 0.05) and rearing frequency (2.75 ± 0.41 and 3.85 ± 0.46, p < 0.01 and p < 0.05, respectively) were lower, latency to center area (49.11 ± 5.87 s and 44.92 ± 8.04 s, p < 0.01 and p < 0.01, respectively), were higher than the control group (8.65 ± 0.49%, 5.37 ± 0.44 and 15.3 ± 3.32 s, respectively). In the immobilization stress-1 group, zinc (12.65 ± 0.1 ppm, p < 0.001), magnesium (170.4 ± 1.7 ppm, p < 0.005) and phosphate (2.76 ± 0.1 ppm, p < 0.05) levels were lower than the control group (13.87 ± 0.16 ppm, 179.31 ± 1.87 ppm and 3.11 ± 0.06 ppm, respectively). In the immobilization stress-2 group, magnesium (171.56 ± 1.87 ppm, p < 0.05), phosphate (2.44 ± 0.07 ppm, p < 0.001) levels were lower, and manganese (373.68 ± 5.76 ppb, p < 0.001) and copper (2.79 ± 0.15 ppm, p < 0.05) levels were higher than the control group (179.31 ± 1.87 ppm, 3.11 ± 0.06 ppm, 327.25 ± 8.35 ppb and 2.45 ± 0.05 ppm, respectively). Our results indicated that 7-day chronic immobilization stress increased anxiety-related behaviors in both stress groups. Zinc, magnesium, phosphate, copper and manganese levels were affected in the brain.

Shall I Move My Right or My Left Hand?

2003 ◽  
Vol 17 (2) ◽  
pp. 69-86 ◽  
Author(s):  
Claudio Babiloni ◽  
Fabio Babiloni ◽  
Filippo Carducci ◽  
Febo Cincotti ◽  
Claudio Del Percio ◽  
...  
Keyword(s):  
Bimanual Coordination ◽  
Central Area ◽  
Eeg Analysis ◽  
Complementary Information ◽  
Left Hand ◽  
Mirror Movements ◽  
Related Potentials ◽  
Motor Acts ◽  
Abstract Event

Abstract Event-related desynchronization/synchronization (ERD/ERS) at alpha (10Hz), beta (20Hz), and gamma (40Hz) bands and movement-related potentials (MRPs) were investigated in right-handed subjects who were “free” to decide the side of unilateral finger movements (“fixed” side as a control). As a novelty, this “multi-modal” EEG analysis was combined with the evaluation of involuntary mirror movements, taken as an index of “bimanual competition.” A main issue was whether the decision regarding the hand to be moved (“free” movements) could modulate ERD/ERS or MRPs overlying sensorimotor cortical areas typically involved in bimanual tasks. Compared to “fixed” movements, “free” movements induced the following effects: (1) more involuntary mirror movements discarded from EEG analysis; (2) stronger vertex MRPs (right motor acts); (3) a positive correlation between these potentials and the number of involuntary mirror movements; (4) gamma ERS over central areas; and (5) preponderance of postmovement beta ERS over left central area (dominant hemisphere). These results suggest that ERD/ERS and MRPs provide complementary information on the cortical processes belonging to a lateralized motor act. In this context, the results on vertex MRPs would indicate a key role of supplementary/cingulate motor areas not only for bimanual coordination but also for the control of “bimanual competition” and involuntary mirror movements.

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