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Iris K. Zemach, Michael E. Rudd; Blocking of achromatic color induction signals by borders of different contrast polarities. Journal of Vision 2002;2(10):106. doi: https://doi.org/10.1167/2.10.106.
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We previously proposed a quantitative model of achromatic color induction based on the idea that underlying neural lightness and darkness induction signals fill in from borders in separate neural filling-in networks before being combined to create an achromatic color signal (Rudd, 2001; Rudd & Arrington, 2001; Rudd & Zemach, 2002). Rudd & Arrington provided evidence that darkness signals are partially blocked when crossing borders that represent a luminance decrement. However, Rudd & Zemach found no evidence for blocking of lightness signals. Here, we further investigate the conditions leading to blocking of induction signals. Two disk-and-surround-ring patterns were presented side-by-side on a flat-panel monitor. The luminance of the right disk was fixed and its surround luminance was varied to manipulate the disk lightness. Three subjects adjusted the luminance of the left disk to achieve a lightness match to the right disk. Four experiments were performed in which the rings had either higher or lower luminance than the background and the disk had either higher or lower luminance than the rings. The results were consistent with the predictions of the model. When ring luminances were higher than the background, plots of the log luminance of the left disk as a function of the log luminance of the right ring were well fit with linear functions that are interpreted as evidence for no blocking of lightness signals. When the ring luminances were lower than the background, these plots were best fit with quadratic functions that are interpreted as evidence for partial blocking of darkness signals. The results generalize our earlier findings and suggest the existence of separate lightness and darkness networks. In these networks, lightness signals spread from their generating borders without being blocked, whereas darkness signals are partially blocked by other borders. Lightness and darkness signals are summed to compute achromatic color.
Rudd, M. E. (2001). Lightness computation by a neural filling-in mechanism. SPIE Proceedings, 4299, 400–413.
Rudd, M. E., & Arrington, K. F. (2001). Darkness filling-in: A neural model of darkness induction. Vision Research, 41, 3649–3662.
Rudd, M. E., & Zemach, I. K. (2002). Contrast, assimilation, and neural edge integration. Vision Sciences Society Absracts.
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