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Yuka Sasaki, Takeo Watanabe; The primary visual cortex fills in color. Journal of Vision 2005;5(8):716. doi: https://doi.org/10.1167/5.8.716.
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© ARVO (1962-2015); The Authors (2016-present)
One of the most important goals of visual processing is to reconstruct adequate representations of surfaces in a scene. Surface representation is thought to be produced mainly in the mid-level vision and that V1 activity is solely due to feedback from the mid-level stage.
However, contradicting empirical and theoretical reports have also been proposed. One reason for this controversy may be due to the tacit assumption that surface representation is made by single processing rather than multiple processing. Surface representation could be a result of many different aspects of processing. Another reason for the controversy may be that most studies have not controlled effects of attention on a surface. Thus, it is necessary to examine how subcomponents of a surface contribute to surface representation with attentional effects controlled.
Here, we measured fMRI signals corresponding to “neon color spreading” that is thought to be due to interactions between mechanisms for two surface subcomponents — color filling-in and illusory contours. In the present study, we used 3T fMRI that provides a fine spatial resolution so that brain activity corresponding to illusory contours and filling-in both as surface subcomponents could be spatially dissociable if surface representation occurs in the retinotopic visual areas. To eliminate or decrease the attentional component of feedback signals, subjects performed an attentionally-challenging task unrelated to the surface perception.
Activity for filling-in was observed only in the primary visual cortex, whereas activity for illusory contours was observed in multiple visual areas. These findings indicate that surface representation is produced by multiple rather than single processing, and that V1 activity for surface representation is not solely from feedback from higher cortical stages.
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