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Contextual effects on binocular matching are evident in primary visual cortex.

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Rideaux, Reuben 
Welchman, Andrew E 


Global context can dramatically influence local visual perception. This phenomenon is well-documented for monocular features, e.g., the Kanizsa triangle. It has been demonstrated for binocular matching: the disambiguation of the Wallpaper Illusion via the luminance of the background. For monocular features, there is evidence that global context can influence neuronal responses as early as V1. However, for binocular matching, the activity in this area of the visual cortex is thought to represent local processing, suggesting that the influence of global context may occur at later stages of cortical processing. Here we sought to test if binocular matching is influenced by contextual effects in V1, using fMRI to measure brain activity while participants viewed perceptually ambiguous "wallpaper" stereograms whose depth was disambiguated by the luminance of the surrounding region. We localized voxels in V1 corresponding to the ambiguous region of the pattern, i.e., where the signal received from the eyes was not predictive of depth, and despite the ambiguity of the input signal, using multi-voxel pattern analysis we were able to reliably decode perceived (near/far) depth from the activity of these voxels. These findings indicate that stereoscopic related neural activity is influenced by global context as early as V1.



Contextual effects, Functional imaging, Primary visual cortex, Stereopsis, Adult, Brain Mapping, Depth Perception, Female, Humans, Magnetic Resonance Imaging, Male, Models, Neurological, Vision, Binocular, Visual Cortex, Young Adult

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Vision Res

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Elsevier BV
Wellcome Trust (095183/Z/10/Z)
Leverhulme Trust (ECF-2017-573)
Isaac Newton Trust (17.08(o))
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (765121)
This work was supported by the Leverhulme Trust (ECF-2017-573 to RR), the Isaac Newton Trust (17.08(o) to RR), and the Wellcome Trust (095183/Z/10/Z to Andrew E Welchman).