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Chen Song, Sam Schwarzkopf, Antoine Lutti, Baojuan Li, Ryota Kanai, Geraint Rees; Effective connectivity in human primary visual cortex predicts inter-individual difference in contextual illusion. Journal of Vision 2013;13(9):115. doi: 10.1167/13.9.115.
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© ARVO (1962-2015); The Authors (2016-present)
Visual perception depends strongly on spatial context. A classic example is the tilt illusion where the perceived orientation of a grating differs from its physical orientation when surrounded by a tilted context. Here we show that such contextual modulation of orientation perception exhibits trait-like inter-individual variability and correlates with effective connectivity within V1. We used functional MRI to measure activity in human early retinotopic cortices (V1-V3) and applied Dynamic Causal Modelling (DCM) to estimate effective connectivity between foveal and peripheral regions of retinotopic cortices that responded to the visual field location of a central grating and that of its surrounding context, respectively. When the grating was placed in spatial context compared to in isolation, intrinsic connectivity from peripheral to foveal regions of V1-V3 increased, and so did feedback connectivity between V1-V3, but no change was observed in feedforward connectivity between V1-V3. This suggests that visual context modulates cortical activity through a combination of intrinsic and feedback connections. Critically, inter-individual differences in the magnitude of the tilt illusion correlated specifically with intrinsic connectivity from peripheral to foveal region of V1 and not V2 or V3. Neither feedforward nor feedback connectivity between V1-V3 or activity in V1-V3 predicted the illusion magnitude. We conclude that spatial context modulated orientation perception through V1 intrinsic connections. Our findings reveal the role of effective connectivity in shaping perceptual content and its inter-individual diversity. This important role played by V1 intrinsic connections challenges conventional theories emphasizing feedback modulation in visual consciousness.
Meeting abstract presented at VSS 2013
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