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Reuben Rideaux, Andrew Welchman; Contextual feedback to V1 neurons shapes binocular matching. Journal of Vision 2018;18(10):123. doi: 10.1167/18.10.123.
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© ARVO (1962-2015); The Authors (2016-present)
Humans infer three dimensional structure of the visual environment by calculating the disparity between images projected into the left and right eyes (i.e., stereopsis). Stereopsis emerges in area V1, where neurons begin receiving binocular input from the lateral geniculate nucleus. Feedforward computations of stereopsis are well established, yet the role of feedback/lateral connections remains unknown. Here we test whether feedback/lateral signals induced by spatial context influence the activity of binocular neurons in V1. We used fMRI to measure activity in the primary visual cortex of participants while they viewed ambiguous "wallpaper" stereograms, i.e., square wave gratings presented with a 180° phase offset between the left and right eyes, which could be perceived as either near or far. We manipulated perceived (near/far) depth of the wallpaper by framing it with either a light- or dark-grey background. Using flickering checkerboard localizers, we identify regions of V1 with receptive fields corresponding to either the frame or wallpaper sections of the stimulus. The near/far identity of the wallpaper pattern was ambiguous; thus, perceived depth could only be inferred by the identity of the frame. Despite this, using multi-voxel pattern analysis we were able to reliably decode perceived depth from the activity of voxels in V1 corresponding to the ambiguous wallpaper region. We then quantified the strength of the depth representation across retinotopic areas and found we were able to reliably decode perceived depth from areas V3A, V4, and V7. These results indicate the involvement of feedback/lateral connections in shaping the activity of disparity selective neurons in V1 during binocular matching.
Meeting abstract presented at VSS 2018
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