scholarly journals Variability in visual cortex size reflects tradeoff between local orientation sensitivity and global orientation modulation

2013 ◽  
Vol 4 (1) ◽  
Author(s):  
Chen Song ◽  
Dietrich S. Schwarzkopf ◽  
Geraint Rees
Keyword(s):  
Visual Cortex ◽  
Local Orientation ◽  
Orientation Sensitivity ◽  
Global Orientation

Are neurons in cat posteromedial lateral suprasylvian visual cortex orientation sensitive? Tests with bars and gratings

1995 ◽  
Vol 12 (1) ◽  
pp. 141-151 ◽  
Author(s):  
Yuri Danilov ◽  
Rodney J. Moore ◽  
Von R. King ◽  
Peter D. Spear
Keyword(s):  
Visual Cortex ◽  
Receptive Fields ◽  
Orientation Tuning ◽  
Orientation Sensitivity ◽  
Tuning Curves ◽  
Preferred Direction ◽  
Response Measures ◽  
Direction Of Movement ◽  
The Difference ◽  
Quantitative Response

AbstractThere is controversy in the literature concerning whether or not neurons in the cat's posteromedial lateral suprasylvian (PMLS) visual cortex are orientation selective. Previous studies that have tested cells with simple bar stimuli have found that few, if any, PMLS cells are orientation selective. Conversely, studies that have used repetitive stimuli such as gratings have found that most or all PMLS cells are orientation selective. It is not known whether this difference in results is due to the stimuli used or the laboratories using them. The present experiments were designed to answer this question by testing individual PMLS neurons for orientation sensitivity with both bar and grating stimuli. Using quantitative response measures, we found that most PMLS neurons respond well enough to stationary flashed stimuli to use such stimuli to test for orientation sensitivity. On the basis of these tests, we found that about 85% of the cells with well-defined receptive fields are orientation sensitive to flashed gratings, and a similar percentage are orientation sensitive to flashed bars. About 80% of the cells were orientation sensitive to both types of stimuli. The preferred orientations typically were similar for the two tests, and they were orthogonal to the preferred direction of movement. The strength of the orientation sensitivity (measured as the ratio of discharge to the preferred and nonpreferred orientations) was similar to both types of stimuli. However, the width of the orientation tuning curves was systematically broader to bars than to gratings. Several hypotheses are considered as to why previous studies using bars failed to find evidence for orientation sensitivity. In addition, a mechanism for the difference in orientation tuning to bars and gratings is suggested.

scholarly journals The Mechanism of Orientation Detection Based on Artificial Visual System

Electronics ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 54
Author(s):  
Xiliang Zhang ◽  
Tang Zheng ◽  
Yuki Todo
Keyword(s):  
Computer Simulation ◽  
Visual System ◽  
Driving Force ◽  
Local Orientation ◽  
Detection Mechanism ◽  
Biological Vision ◽  
Global Orientation ◽  
Orientation Information ◽  
Orientation Detection ◽  
Visual Cortex Neurons

As an important part of the nervous system, the human visual system can provide visual perception for humans. The research on it is of great significance to improve our understanding of biological vision and the human brain. Orientation detection, in which visual cortex neurons respond only to linear stimuli in specific orientations, is an important driving force in computer vision and biological vision. However, the principle of orientation detection is still unknown. This paper proposes an orientation detection mechanism based on dendrite calculation of local orientation detection neurons. We hypothesized the existence of orientation detection neurons that only respond to specific orientations and designed eight neurons that can detect local orientation information. These neurons interact with each other based on the nonlinearity of dendrite generation. Then, local orientation detection neurons are used to extract local orientation information, and global orientation information is deduced from local orientation information. The effectiveness of the mechanism is verified by computer simulation, which shows that the machine can perform orientation detection well in all experiments, regardless of the size, shape, and position of objects. This is consistent with most known physiological experiments.

Orientation sensitivity of the cat assessed from evoked potentials: central and peripheral contributions

1985 ◽  
Vol 53 (5) ◽  
pp. 1287-1302 ◽  
Author(s):  
J. S. Tootle ◽  
M. A. Berkley
Keyword(s):  
Visual Cortex ◽  
Evoked Potentials ◽  
Visual Stimulus ◽  
Interstimulus Interval ◽  
Optic Tract ◽  
Stimulus Presentation ◽  
Forward Direction ◽  
Orientation Sensitivity ◽  
Retinal Input ◽  
Band Pass

To estimate contour-orientation sensitivity of the cat and the degree to which precortical processing contributes to such estimates, the amplitude of visually evoked potentials (VEP) recorded from the visual cortex of cats in response to a visual stimulus (S2) presented at various intervals after presentation of another visual stimulus (S1) was measured under several conditions. Recordings were made when both stimuli were presented through one eye (monoptic condition) or when S1 was presented to one eye and S2 to the other (dichoptic condition). In some experiments, simultaneous recordings were made from the optic tract and visual cortex. The stimuli were pairs of sinusoidal gratings with a spatial frequency of 0.5 cycles/deg and of various orientations. Each stimulus was presented by stepping the grating contrast from 0.0 (adapting field) to 0.5 for 50 ms. The intervals between the presentation of the two test stimuli (S1 and S2) was varied from 0 to 1,550 ms, and on different trials the orientation of the S2 grating relative to that of S1 was varied from 0 to 90 degrees. Results showed that under monoptic conditions, the VEP to the second stimulus (S2) was reduced by presentation of the first stimulus (S1) when the interstimulus interval was less than 200 ms, whereas under dichoptic conditions, the response to S2 was reduced with interstimulus intervals less than 75 ms. The response reduction was always in a forward direction (e.g., reduced S2 response), increased in magnitude with decreases in the interstimulus interval, and was larger under monoptic conditions than under dichoptic conditions. The response reduction produced monoptically was orientation selective in that it was greatest when the orientation of S1 and S2 was the same, and it recovered by half when the orientation differed by 6 to 15 degrees (orientation half-band pass). In some cortical recordings, the orientation-selective response reduction was superimposed on a response reduction that was not selective for S2 orientation. Stimultaneous recording in the optic tract also showed a response reduction of S2 response that was not orientation selective, suggesting that precortical neural elements contribute to the cortical VEP. With dichoptic stimulus presentation an orientation-nonspecific response reduction was obtained. We hypothesized that binocular inhibitory effects, resulting from disparate retinal input, produced this surprising finding. The results demonstrate that the VEP recorded at the cortex can be used to estimate orientation sensitivity, but that response interactions in peripheral (precortical) neural elements can contribute to such estimates.

Global Orientation Disrupts the Detection of a Similar Local Orientation

Perception ◽  
1997 ◽  
Vol 26 (10) ◽  
pp. 1259-1270 ◽  
Author(s):  
Johan Lauwereyns ◽  
Géry d'Ydewalle
Keyword(s):  
Visual Search ◽  
Target Letter ◽  
Target Line ◽  
Local Processing ◽  
Local Orientation ◽  
Critical Feature ◽  
Line Segments ◽  
Global Orientation ◽  
Global And Local

Two experiments were carried out with organised displays in order to examine the role of similarity between global and local orientation in visual search. In both experiments, distractors were organised to form a diagonal line of plus or minus 45°. In experiment 1, target displays were presented tachistoscopically. Participants searched for a target letter ‘Q’ among distractor letters ‘O’. In experiment 2, participants performed a heterogeneity task with target line segments that could have an orientation of either plus or minus 45°. The target appeared partly or completely inside a distractor circle. In both experiments, the target was more difficult to detect when the critical feature aligned with the slope of the global diagonal than when the feature did not align. Taken together, the two experiments suggested a sequential global-to-local processing in which the orientation of the global figure disrupts the detection of a similar local orientation.

Does Local or Global Orientation Determine the McCollough Effect?

1997 ◽  
Vol 84 (3) ◽  
pp. 723-727
Author(s):  
Tooru Yoshioka ◽  
Shigeru Ichihara
Keyword(s):  
Perceptual Organization ◽  
Test Pattern ◽  
Important Determinant ◽  
Mccollough Effect ◽  
Local Orientation ◽  
Global Features ◽  
Global Orientation

In this research, the McCollough effect was observed by using an ambiguous test pattern of coarse gratings made out of fine gratings. Coarse gratings meet at right angles to fine gratings. The global features (coarse gratings) in the test pattern became more salient if the test pattern was blurred, and the frequency of the McCollough effect, corresponding to the global orientation of the test pattern, increased with the increase of the extent of blur. The McCollough effects corresponding to the local orientation of the test pattern occurred frequently if the subjects adapted to fine gratings before viewing the test pattern, whereas the McCollough effects corresponding to the global orientation of the test pattern occurred frequently if the subjects adapted to coarse gratings. Our results indicate that the perceptual organization is an important determinant in the McCollough effect.

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