Global Factors in the Hermann Grid Illusion

Perception ◽  
1984 ◽  
Vol 13 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Jeremy M Wolfe
Keyword(s):  
Receptive Fields ◽  
Illusion Magnitude ◽  
Local Model ◽  
Hermann Grid Illusion

Most explanations of the Hermann grid illusion are local in nature. For example, in Baumgartner's model the effect is generated by the response of cells having concentric on—off or off—on receptive fields. Such models predict that the magnitude of the illusion at a given intersection should be the same whether that intersection is viewed in isolation or in conjunction with other intersections in a grid. Two experiments are reported. The first demonstrates that illusion magnitude grows with the number of intersections. The second shows that this growth is seen when the intersections are arranged in an orderly grid but not when they are placed irregularly. These results suggest that a purely local model for the Hermann grid illusion is not a complete explanation. Global factors must be involved.

The Hermann Grid Illusion: A Tool for Studying Human Perceptive Field Organization

Perception ◽  
1994 ◽  
Vol 23 (6) ◽  
pp. 691-708 ◽  
Author(s):  
Lothar Spillmann
Keyword(s):  
Receptive Field ◽  
Ganglion Cells ◽  
Receptive Fields ◽  
Retinal Eccentricity ◽  
Cortical Cells ◽  
Perceptive Field ◽  
Neurophysiological Mechanisms ◽  
Field Organization ◽  
Hermann Grid Illusion ◽  
Retinal Receptive Fields

Psychophysical research on the Hermann grid illusion is reviewed and possible neurophysiological mechanisms are discussed. The illusion is most plausibly explained by lateral inhibition within the concentric receptive fields of retinal and/or geniculate ganglion cells, with contributions by the binocular orientation-specific cortical cells. Results may be summarized as follows: (a) For a strong Hermann grid illusion to be seen bar width must be matched to the mean size of receptive-field centers at any given retinal eccentricity. (b) With the use of this rationale, the diameter of foveal perceptive-field centers (the psychophysical correlate of receptive-field centers) has been found to be in the order of 4–5 min arc and that of total fields (centers plus surrounds) 18 min arc. These small diameters explain why the illusion tends to be absent in foveal vision. (c) With increasing distance from the fovea, perceptive-field centers increase to 1.7 deg at 15 deg eccentricity and then to 3.4 deg at 60 deg eccentricity. This doubling in diameter agrees with the change in size of retinal receptive-field centers in the monkey. (d) The Hermann grid illusion is diminished with dark adaptation. This finding is consistent with the reduction of the center—surround antagonism in retinal receptive fields. (e) The illusion is also weakened when the grid is presented diagonally, which suggests a contribution by the orientation-sensitive cells in the lateral geniculate nucleus and visual cortex. (f) Strong induction effects, similar to the bright and dark spots in the Hermann grid illusion, may be elicited by grids made of various shades of grey; and by grids varying only in chroma or hue. Not accounted for are: the illusory spots occurring in an outline grid ie with hollow squares, and the absence of an illusion when extra bars are added to the grid. Alternative explanations are discussed for the spurious lines connecting the illusory spots along the diagonals and the fuzzy dark bands traversing the rhombi in modified Hermann grids.

The Curved Grid Non-Illusions

2017 ◽  
Author(s):  
János Geier ◽  
Mariann Hudák
Keyword(s):  
Statistical Analysis ◽  
Retinal Ganglion Cells ◽  
Line Width ◽  
Ganglion Cells ◽  
Receptive Fields ◽  
Retinal Ganglion ◽  
Illusory Effect ◽  
Grid Line ◽  
Wide Range ◽  
Hermann Grid Illusion

The generally accepted explanation of the Hermann grid illusion is Baumgartner’s hypothesis that the illusory effect is generated by the response of retinal ganglion cells with concentric ON-OFF or OFF-ON receptive fields. To challenge this explanation, some simple distortions to the grid lines were introduced that make the illusion disappear totally, while all preconditions of Baumgartner’s hypothesis remained unchanged. Psychophysical experiments in which the distortion tolerance was measured showed the level of distortion at which the illusion disappears at a given type of distortion for a given subject. Statistical analysis shows that the distortion tolerance is independent of grid-line width within a wide range and of the type of distortion, except when one side of each line remains straight. The conclusion is the main cause of the Hermann grid illusion is the straightness of the edges of the grid lines. Similar results have been obtained in the scintillating grid.

The Scintillating Grid

2017 ◽  
Author(s):  
Bernd Lingelbach
Keyword(s):  
Visual Perception ◽  
Receptive Fields ◽  
European Conference ◽  
Low Pass ◽  
Hermann Grid Illusion

The scintillating grid was first presented at the European Conference on Visual Perception in Tübingen in 1995. At the time, the prevailing explanation of the Hermann grid illusion was in terms of the arrangement of the receptive fields on the retina. The minor modification of having a grey instead of a white grid with white dots at the intersections produced a strikingly new and powerful illusion. Instead of the white dots, dark black dots are seen to “blink” and appear even darker in intensity than the black printer’s ink of the square. They then disappear again to reappear immediately somewhere else. The dark diagonals that appear from time to time fitted more to low-pass filtering. The study of low-pass filtered Hermann grids led to the discovery of the scintillating grid and several variants. To this day this illusion still has not been fully explained.

The Hermann Grid Illusion Revisited

Perception ◽  
10.1068/p5447 ◽  
2005 ◽  
Vol 34 (11) ◽  
pp. 1375-1397 ◽  
Author(s):  
Peter H Schiller ◽  
Christina E Carvey
Keyword(s):  
Ganglion Cell ◽  
Retinal Ganglion Cell ◽  
Ganglion Cells ◽  
Receptive Fields ◽  
Alternative Theory ◽  
Cell Theory ◽  
Retinal Ganglion ◽  
Illusory Effect ◽  
Differential Responses ◽  
Hermann Grid Illusion

The Hermann grid illusion consists of smudges perceived at the intersections of a white grid presented on a black background. In 1960 the effect was first explained by a theory advanced by Baumgartner suggesting the illusory effect is due to differences in the discharge characteristics of retinal ganglion cells when their receptive fields fall along the intersections versus when they fall along non-intersecting regions of the grid. Since then, others have claimed that this theory might not be adequate, suggesting that a model based on cortical mechanisms is necessary [Lingelbach et al, 1985 Perception14(1) A7; Spillmann, 1994 Perception23 691–708; Geier et al, 2004 Perception33 Supplement, 53; Westheimer, 2004 Vision Research44 2457–2465]. We present in this paper the following evidence to show that the retinal ganglion cell theory is untenable: (i) varying the makeup of the grid in a manner that does not materially affect the putative differential responses of the ganglion cells can reduce or eliminate the illusory effect; (ii) varying the grid such as to affect the putative differential responses of the ganglion cells does not eliminate the illusory effect; and (iii) the actual spatial layout of the retinal ganglion cell receptive fields is other than that assumed by the theory. To account for the Hermann grid illusion we propose an alternative theory according to which the illusory effect is brought about by the manner in which S1 type simple cells (as defined by Schiller et al, 1976 Journal of Neurophysiology39 1320–1333) in primary visual cortex respond to the grid. This theory adequately handles many of the facts delineated in this paper.

Ultrastructure of developing visual cortical synapses in the cat superior colliculus

1991 ◽  
Vol 49 ◽  
pp. 156-157
Author(s):  
Caroline A. Miller ◽  
Laura L. Bruce
Keyword(s):  
Superior Colliculus ◽  
Phosphate Buffer ◽  
Receptive Fields ◽  
Visual Cortical Area ◽  
Cortical Synapses ◽  
Visual Cortical ◽  
And Function ◽  
Phosphate Buffered Saline ◽  
The Brain ◽  
Cat Superior Colliculus

The first visual cortical axons arrive in the cat superior colliculus by the time of birth. Adultlike receptive fields develop slowly over several weeks following birth. The developing cortical axons go through a sequence of changes before acquiring their adultlike morphology and function. To determine how these axons interact with neurons in the colliculus, cortico-collicular axons were labeled with biocytin (an anterograde neuronal tracer) and studied with electron microscopy.Deeply anesthetized animals received 200-500 nl injections of biocytin (Sigma; 5% in phosphate buffer) in the lateral suprasylvian visual cortical area. After a 24 hr survival time, the animals were deeply anesthetized and perfused with 0.9% phosphate buffered saline followed by fixation with a solution of 1.25% glutaraldehyde and 1.0% paraformaldehyde in 0.1M phosphate buffer. The brain was sectioned transversely on a vibratome at 50 μm. The tissue was processed immediately to visualize the biocytin.

On velocity selection for needle-crystals in a fully non-local model of solidification

1987 ◽  
Vol 48 (4) ◽  
pp. 547-552 ◽  
Author(s):  
B. Caroli ◽  
C. Caroli ◽  
C. Misbah ◽  
B. Roulet
Keyword(s):  
Local Model ◽  
Non Local ◽  
Selection For ◽  
Velocity Selection
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