Binocular properties of curvature-encoding mechanisms revealed through two shape after-effects

Gheorghiu, Elena; Kingdom, Frederick A. A.; Thai, Minh-Thu; Sampasivam, Lavanya

doi:10.1016/j.visres.2009.04.010

Cited by 14 publications

(21 citation statements)

References 79 publications

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“…Because of variations in the overall magnitude of the shape-frequency aftereffects across subjects, the data for each subject has been normalized to the C/C condition. The experimental protocol was identical to that described in Gheorghiu and Kingdom (2012b), and the data replicate both the earlier findings of Kingdom and Prins (2005) using continuous contours, as well as data from various subsets of these four conditions reported in previous studies, for example the studies that investigated the spatial (Gheorghiu & Kingdom, 2012b), binocular (Gheorghiu et al, 2009b), chromatic (Gheorghiu & Kingdom, 2012a) and motion (Gheorghiu & Kingdom, 2012c properties of surround suppression.…”

Section: Experimental Evidence For De-texturizationsupporting

confidence: 68%

“…Besides local orientation, texture-surround suppression is selective for stereoscopic-depth (Gheorghiu et al, 2009b), and both global motion direction and temporal frequency (Gheorghiu & Kingdom, 2012c. However it is only weakly selective to color direction, and when the central adaptor contour and test are both achromatic, the magnitude of suppression is agnostic to the particular color of the surround (Gheorghiu & Kingdom, 2012a).…”

Section: Tuning Of Surround Suppressionmentioning

confidence: 99%

“…Of course, this is entirely consistent with V1 neurons feed-forwarding their 'de-texturized' responses into shape-selective neurons in higher visual areas. Indirect evidence in support of V4 as the site of de-texturization comes from Gheorghiu et al (2009b) finding that the shape-frequency after-effect was inhibited by parallel surround texture only when the surround was in the same stereoscopic depth plane as the central adaptor contour. Neurons in V4 are predominantly sensitive to oriented bars at near-disparities (Hinkle & Connor, 2001, 2002Watanabe et al, 2002), which has been suggested to be important for figure-ground segregation.…”

Section: Relevance Of Contour Detection and Crowding Studiesmentioning

confidence: 99%

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Contextual modulation as de-texturizer

2014

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Contextual modulation refers to the effect of texture placed outside of a neuron's classical receptive field as well as the effect of surround texture on the perceptual properties of variegated regions within. In this minireview, we argue that one role of contextual modulation is to enhance the perception of contours at the expense of textures, in short to de-texturize the image. The evidence for this role comes mainly from three sources: psychophysical studies of shape after-effects, computational models of neurons that exhibit iso-orientation surround inhibition, and fMRI studies revealing specialized areas for contour as opposed to texture processing. The relationship between psychophysical studies that support the notion of contextual modulation as de-texturizer and those that investigate contour integration and crowding is discussed.

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Section: Experimental Evidence For De-texturizationsupporting

confidence: 68%

Section: Tuning Of Surround Suppressionmentioning

confidence: 99%

Section: Relevance Of Contour Detection and Crowding Studiesmentioning

confidence: 99%

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Contextual modulation as de-texturizer

2014

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“…Kingdom and Prins (2009) hypothesized that neurons exhibiting iso-orientation surround suppression feed their responses into contour-shape-coding neurons located in higher visual areas, with the functional role of isoorientation surround suppression being to separate isolated contours for the purpose of contour shape encoding. Although computational models suggest that contours that are orthogonally-oriented with their surrounds are enhanced by cross-orientation facilitation (Huang et al, 2008), none of our studies of TSSCS (Gheorghiu et al, 2009a;Gheorghiu et al, 2009b;Kingdom & Prins, 2009) have found evidence for facilitation.…”

Section: Introductioncontrasting

confidence: 65%

“…The importance of TSSCS is that it is the first expression of the effect of a texture surround on the encoding of the shape of a fully visible contour. Although subsequent studies have explored the selectivity of TSSCS to attributes such as stereoscopicdepth, color, and motion (Gheorghiu, Kingdom, & Varshney, 2009a;Gheorghiu, Kingdom, Thai, & Sampasivam, 2009b;, we still know very little about how TSSCS operates and over what spatial extent. In this communication we address these issues.…”

Section: Introductionmentioning

confidence: 99%

Local and global components of texture-surround suppression of contour-shape coding

Gheorghiu

Kingdom

2012

Journal of Vision

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Evidence that contour-shapes and texture-shapes are processed by different mechanisms included the finding that contour-shape aftereffects are reduced when the adaptation stimulus is a texture made of contours rather than a single contour. This phenomenon has been termed texture-surround suppression of contour-shape, or TSSCS. How does TSSCS operate and over what spatial extent? We measured the postadaptation shift in the apparent shape frequency of a single sinusoidal-shaped contour as a function of the number of contours in the adaptor stimulus. Contours were Gabor strings in which the Gabor orientations were either tangential (snakes) or orthogonal (ladders) to the path of the contour. We found that for extended surrounds, the aftereffect was strongly reduced when the surround contours were the same as the central adaptor contour, but not when the Gabors making up the surround contours were opposite-in-orientation to those of the central adaptor. For near surrounds, the aftereffect in a snake contour was unaffected by same-orientation but strongly suppressed by opposite-orientation surrounds, whereas the aftereffect for a ladder-contour was suppressed equally by both same- and opposite-orientation near surrounds. Finally, the strength of surround suppression decreased gradually with increasing spatial separation between center and surround. These results indicate that there are two components to texture-surround suppression in our shape aftereffect: one that is sensitive to opposite-orientation texture surrounds, operates locally, and disrupts contour-processing; the other that is sensitive to same-orientation texture surrounds, is spatially extended, and prevents the shape of the contour from being processed as a contour. We also demonstrate that the observed shape aftereffects are not due to changes in the apparent shape-frequency of the adaptors or the precision with which their shape-frequency is encoded, indicating that TSSCS is not an instance of crowding.

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