Contextual modulation as de-texturizer

Gheorghiu, Elena; Kingdom, Frederick A. A.; Petkov, Nicolai

doi:10.1016/j.visres.2014.08.013

Cited by 25 publications

(36 citation statements)

References 105 publications

(149 reference statements)

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“…In particular, iso-orientation surround suppression could suppress the encoding of uniform texture (Grigorescu et al, 2003;Wei et al, 2013;Schmid and Victor, 2014) and enhance the representation of object boundaries. Our discovery of stronger responses to shapes in V4 is consistent with this process called detexturization (Gheorghiu et al, 2014) and with psychophysical studies that argue for a primary role for boundary information in object recognition (Biederman and Ju, 1988;Davidoff and Ostergaard, 1988;Elder and Velisavljevic, 2009;Fu et al, 2016). Because neurons in V1 and V2 primarily encode surface characteristics (but see border-ownership coding in V2) (Zhou et al, 2000), a preference for encoding objects in V4 could reflect its fundamental role in the computation of object-based representations in the ventral stream.…”

Section: Emergence Of Object Representation In V4supporting

confidence: 84%

Neural Coding for Shape and Texture in Macaque Area V4

2019

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The distinct visual sensations of shape and texture have been studied separately in cortex; therefore, it remains unknown whether separate neuronal populations encode each of these properties or one population carries a joint encoding. We directly compared shape and texture selectivity of individual V4 neurons in awake macaques (1 male, 1 female) and found that V4 neurons lie along a continuum from strong tuning for boundary curvature of shapes to strong tuning for perceptual dimensions of texture. Among neurons tuned to both attributes, tuning for shape and texture were largely separable, with the latter delayed by ϳ30 ms. We also found that shape stimuli typically evoked stronger, more selective responses than did texture patches, regardless of whether the latter were contained within or extended beyond the receptive field. These results suggest that there are separate specializations in mid-level cortical processing for visual attributes of shape and texture.

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Section: Emergence Of Object Representation In V4supporting

confidence: 84%

Neural Coding for Shape and Texture in Macaque Area V4

2019

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“…In the following we propose iso-orientation surround suppression (see Gheorghiu, Kingdom, & Petkov, 2014, for a recent review) as a low-level candidate mechanism that could potentially account for the observed asymmetry. Iso-orientation surround suppression is a cortical mechanism by which neurons are inhibited by activity of other neurons in their local surround.…”

Section: Potential Causes Of the Effectmentioning

confidence: 99%

Testing the role of luminance edges in White's illusion with contour adaptation

et al. 2015

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White's illusion is the perceptual effect that two equiluminant gray patches superimposed on a black-and-white square-wave grating appear different in lightness: A test patch placed on a dark stripe of the grating looks lighter than one placed on a light stripe. Although the effect does not depend on the aspect ratio of the test patches, and thus on the amount of border that is shared with either the dark or the light stripe, the context of each patch must, in a yet to be specified way, influence their lightness. We employed a contour adaptation paradigm (Anstis, 2013) to test the contribution of each of the test patches' edges to the perceived lightness of the test patches. We found that adapting to the edges that are oriented parallel to the grating slightly increased the lightness illusion, whereas adapting to the orthogonal edges abolished, or for some observers even reversed, the lightness illusion. We implemented a temporal adaptation mechanism in three spatial filtering models of lightness perception, and show that the models cannot account for the observed adaptation effects. We conclude that White's illusion is largely determined by edge contrast across the edge orthogonal to the grating, whereas the parallel edge has little or no influence. We suggest mechanisms that could explain this asymmetry.

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“…The selectivities shown here for luminance polarity and contrast in the context of interactions between contour-shape and texture-shape perception are consistent with one aim of vision being to segregate contours that define objects from those that form textured surfaces. It has been suggested that TSSCS is likely mediated by extraclassical receptive field neurons in early visual areas such as V1 that feed forward their responses into shape-selective neurons in intermediateto-higher visual areas (Gheorghiu et al, 2014). Thus, the selectivity of TSSCS to luminance polarity and contrast may constitute an important neural substrate underlying efficient figure (object)-ground (texture) segregation and image segmentation.…”

Section: Resultsmentioning

confidence: 99%

“…Textures can modulate our perception of the shapes of contours they surround (Gheorghiu & Kingdom, 2012a, 2012bGheorghiu, Kingdom, & Petkov, 2014;Grigorescu, Petkov, & Westenberg, 2003, 2004Kingdom & Prins, 2009;Z. Li, 1999Z.…”

Section: Introductionmentioning

confidence: 99%

“…We have termed this phenomenon texture-surround suppression of contour shape or TSSCS Gheorghiu, Kingdom, Thai, & Sampasivam, 2009;Kingdom & Prins, 2009). Gheorghiu, Kingdom, and Petkov (2014) proposed that this type of contextual influence reflects a general-purpose mechanism that ''detexturizes'' an image by enhancing the representation of isolated contours at the expense of contours that are embedded in textures. In other words, contours that are part of textures are prevented from contributing to object-shape perception while continuing to contribute to texture-shape perception.…”

Section: Introductionmentioning

confidence: 99%

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Luminance-contrast properties of texture-shape and texture-surround suppression of contour shape

Gheorghiu

Kingdom

2019

Journal of Vision

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Studies have revealed that textures suppress the processing of the shapes of contours they surround. One manifestation of texture-surround suppression is the reduction in the magnitude of adaptation-induced contour-shape aftereffects when the adaptor contour is surrounded by a texture. Here we utilize this phenomenon to investigate the nature of the first-order inputs to texture-surround suppression of contour shape by examining its selectivity to luminance polarity and the magnitude of luminance contrast. Stimuli were constructed from sinusoidal-shaped strings of either ''bright'' or ''dark'' elongated Gaussians. Observers adapted to pairs of contours, and the aftereffect was measured as the shift in the apparent shape frequency of subsequently presented test contours. We found that the suppression of the contour-shape aftereffect by a surround texture made of similar contours was maximal when the adaptor's center and surround contours were of the same polarity, revealing polarity specificity of the surround-suppression effect. We also measured the effect of varying the relative contrasts of the adaptor's center and surround and found that the reduction in the contour-shape aftereffect was determined by the surround-to-center contrast ratio. Finally, we measured the selectivity to luminance polarity of the texture-shape aftereffect itself and found that it was reduced when the adaptors and tests were of opposite luminance polarity. We conclude that texture-surround suppression of contour-shape as well as texture-shape processing itself depend on ''on-off'' luminance-polarity channel interactions. These selectivities may constitute an important neural substrate underlying efficient figureground segregation and image segmentation.

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Contextual modulation as de-texturizer

Cited by 25 publications

References 105 publications

Neural Coding for Shape and Texture in Macaque Area V4

Neural Coding for Shape and Texture in Macaque Area V4

Testing the role of luminance edges in White's illusion with contour adaptation

Luminance-contrast properties of texture-shape and texture-surround suppression of contour shape

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