Neural correlates of color - selective metacontrast in human early 2 retinotopic areas 3 4

25 Metacontrast is a visual illusion in which the visibility of a target stimulus is 26 virtually lost when immediately followed by a non-overlapping mask stimulus. 27 For a colored target, metacontrast is color-selective, with target visibility 28 markedly reduced when the mask and target are the same color, but only 29 slightly reduced when the colors differ. The present study investigated neural 30 correlates of color-selective metacontrast for cone-opponent red and green 31 stimuli in the human V1, V2 and V3 using functional magnetic resonance 32 imaging. Neural activity was suppressed when the target was rendered less 33 visible by the same-colored mask, and the suppression was localized in the 34 cortical region retinotopically representing the target, correlating with the 35 perceptual topography of visibility/invisibility, rather than the physical 36 topography of the stimulus. Retinotopy-based group analysis found that 37 activity suppression was statistically significant for V2 and V3, and that its 38 localization to the target region was statistically significant for V2. These results 39 suggest that retinotopic color representations in early visual areas, especially in 40 V2, are closely linked to the visibility of color. 41 42