Dynamics of unconscious contextual effects in orientation processing

Mareschal, Isabelle; Clifford, Colin W. G.

doi:10.1073/pnas.1200952109

Cited by 25 publications

(34 citation statements)

References 45 publications

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“…In a recent paper by Mareschal and Clifford (2012), the authors suggested that a single mechanism operating in the early stages of visual processing (before conscious perception of the surround) could account for both the tilt repulsion and attraction. They used a reversecorrelation technique, in which the surround orientation was changed every 12 ms making it invisible to observers.…”

Section: Discussionmentioning

confidence: 98%

“…In order to demonstrate different mechanisms or explore the level of segmentation information processing, a backward noise masking of the surround (Clifford & Harris, 2005) or a rapid reverse-correlation method (Mareschal & Clifford, 2012) could be useful. In a recent paper by Mareschal and Clifford (2012), the authors suggested that a single mechanism operating in the early stages of visual processing (before conscious perception of the surround) could account for both the tilt repulsion and attraction.…”

Section: Discussionmentioning

confidence: 99%

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Segmentation decreases the magnitude of the tilt illusion

2013

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In the tilt illusion, the perceived orientation of a target grating depends strongly on the orientation of a surround. When the orientations of the center and surround gratings differ by a small angle, the center grating appears to tilt away from the surround orientation (repulsion), whereas for a large difference in angle, the center appears to tilt toward the surround orientation (attraction). In order to understand how segmentation/perceptual grouping of the center and surround affect the magnitude of the tilt illusion, we conducted three psychophysical experiments in which we measured observers' perception of center orientation as a function of center-surround relative contrast, relative disparity depth, and geometric features such as occlusion and collinearity. All of these manipulations affected the strength of perceived orientation bias in the center. Our results suggest that if stronger segmentation/perceptual grouping is induced between the center and surround, the tilt repulsion bias decreases/increases. A grouping-dependent tilt illusion plays an important role in visual search and detection by enhancing the sensitivity of our visual system to feature discrepancies, especially in relatively homogenous environments.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Segmentation decreases the magnitude of the tilt illusion

2013

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“…Perceptual integration ensured that the rapid succession of surround gratings effectively masked one another so that observers were at all times blind to their orientation. Mareschal and Clifford (2012) nonetheless found that direct and indirect tilt illusions occurred reliably and over a similar time course, implicating a single mechanism operating in the early stages of visual processing before conscious extraction of the surround orientation.…”

Section: Does the Tilt Illusion Require Awareness Of The Surround Orimentioning

confidence: 91%

“…The influence of the surround declines with distance from the test (Mareschal & Clifford, 2013;Virsu & Taskinen, 1975). Repulsive and attractive effects do not require awareness of the surround orientation (Mareschal & Clifford, 2012) and are observed not only for orientation defined by (first-order) modulations in luminance but also for (second-order) contrast modulations (Smith, Clifford, & Wenderoth, 2001;Wenderoth, Clifford, & Ma Wyatt, 2001) and purely chromatic modulations (Clifford et al, 2003a(Clifford et al, , 2003b.…”

Section: Introduction: Basic Phenomenology and Early Ideasmentioning

confidence: 94%

“…Mareschal and Clifford (2012) designed a reverse-correlation technique to measure the influence of the surround on the perception of the target as a function of surround orientation and timing. Subjects made forced-choice judgments of whether objectively vertical gratings presented at 2 s intervals appeared tilted clockwise or anti-clockwise from vertical.…”

Section: Does the Tilt Illusion Require Awareness Of The Surround Orimentioning

confidence: 99%

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The tilt illusion: Phenomenology and functional implications

Clifford

2014

Vision Research

123

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The perceived orientation of a line or grating is affected by the orientation structure of the surrounding image: the tilt illusion. Here, I offer a selective review of the literature on the tilt illusion, focusing on functional aspects. The review explores the merits of mechanistic accounts of the tilt illusion based upon sensory gain control in which neuronal responses are normalized by the pooled activity of other units. The role of inhibition between orientation-selective neurons is discussed, and it is argued that their associated disinhibition must also be taken into account in order to model the full angular dependence of the tilt illusion on surround orientation. Parallels are drawn with adaptation as modulation by the temporal rather than spatial context within which an image fragment is processed. The chromatic selectivity of the tilt illusion and the extent of its dependence on the visibility of the surround are used to infer characteristics of the neuronal normalization pools and the loci in the cortical processing hierarchy at which gain control operates. Finally, recent evidence is discussed as to the possible clinical relevance of the tilt illusion as a biomarker for schizophrenia.

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Contextual influence on the tilt after-effect in foveal and para-foveal vision

et al. 2015

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A sensory stimulus can only be properly interpreted in light of the stimuli that surround it in space and time. The tilt illusion (TI) and tilt after-effect (TAE) provide good evidence that the perception of a target depends strongly on both its spatial and temporal context. In previous studies, the TI and TAE have typically been investigated separately, so little is known about their co-effects on visual perception and information processing mechanisms. Here, we considered the influence of the spatial context and the temporal effect together and asked how centersurround context affects the TAE in foveal and parafoveal vision. Our results showed that different center-surround spatial patterns signifi cantly affected the TAE for both foveal and para-foveal vision. In the fovea, the TAE was mainly produced by central adaptive gratings. Cross-oriented surroundings significantly inhibited the TAE, and iso-oriented surroundings slightly facilitated it; surround inhibition was much stronger than surround facilitation. In the para-fovea, the TAE was mainly decided by the surrounding patches. Likewise, a cross-oriented central patch inhibited the TAE, and an iso-oriented one facilitated it, but there was no significant difference between inhibition and facilitation. Our findings demonstrated, at the perceptual level, that our visual system adopts different mechanisms to process consistent or inconsistent central-surround orientation information and that the unequal magnitude of surround inhibition and facilitation is vitally important for the visual system to improve the detectability or discriminability of novel or incongruent stimuli.

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Dynamics of unconscious contextual effects in orientation processing

Cited by 25 publications

References 45 publications

Segmentation decreases the magnitude of the tilt illusion

Segmentation decreases the magnitude of the tilt illusion

The tilt illusion: Phenomenology and functional implications

Contextual influence on the tilt after-effect in foveal and para-foveal vision

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