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Ryota Kanai, Martin Sereno, Walsh Vincent; Representations of physical and perceived colour-motion conjunction in early visual cortex. Journal of Vision 2010;10(7):919. doi: https://doi.org/10.1167/10.7.919.
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© ARVO (1962-2015); The Authors (2016-present)
In order to reveal how combinations of visual features are represented in early visual areas (V1, V2, V3, V3A and V4), we examined whether they show adaptation to colour-motion conjunctions using functional MRI. Further, we investigated which visual areas show adaptation to perceived conjunctions rather than physical conjunctions using the steady-state misbinding (Wu, Kanai & Shimojo, 2004), which allows separation of perceived conjunction from physical conjunction. Adaptation to physical and perceived conjunctions was evaluated within regions of interest (ROIs) corresponding to the patches of the visual field where misbinding was induced. In one condition, peripheral conjunctions alternated physically every 2 seconds, but the central part remained constant, resulting in a constant percept (physical alternation condition). In a second condition, the central part alternated physically every 2 seconds, but the peripheral target patches remained physically constant (perceptual alternation condition). Two additional conditions were included as the baseline conditions in which both the central and peripheral patches stayed constant or both alternated. We found that most of the early visual areas adapted to physical stimulus combinations, suggesting that these areas encode physical colour-motion combinations even when the percept alternated. The only exception was V3A, which showed stronger adaptation to perceived combinations rather than physical combinations. These results indicate that colour and motion may not be segregated as previously believed. Furthermore, the adaptation to perceived combination in V3A suggests that conscious perception of colour-motion conjunction may be directly represented at an intermediate stage of visual processing.
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