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C. Q. Wu; Afterimages and Complementarity in Color Vision. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2735.
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Nowadays many authors invoke Hering's Opponent-Process Theory (OPT) to explain negative and complementary afterimages. However, the fact is that the colors exhibited in afterimages are complementary to their original ones - not the opponent colors (particularly, the Red-Green pair) assumed in OPT. Here I demonstrate that OPT is an incorrect (or incomplete at best) explanation for afterimages in specific and many other color phenomena in general.
The phenomenon used in this study is the so-called "Flight-Of-Colors" (FOC): If one looks at an intense bright light for a short duration and then closes eyes, one will experience an afterimage consisting of a sequence of colors and lasting up to several minutes. Would the colors manifested in this phenomenon turn out to be every possible hues? or just the 4 unique hues subsumed in OPT? or in other ways? Many investigators had described the colors in FOC, but it appears that they had used color names rather inconsistently - for instance, some authors had used the term "Greenish-Blue" or just "Blue" for the color that nowadays we would call "Cyan". Therefore I have made many observations staring directly and briefly (< 1 second) at Northern California's bright sun and then closing or opening eyes to experience FOC.
(1) The FOC afterimage usually consists of one or two rings surrounding an inner disk; (2) With closed eyes the predominant colors occurring in FOC are Cyan, Magenta, and Yellow; (3) With open eyes and projecting FOC to a white background the colors would immediately change to their complementary ones - this is possibly the reason why Helmholtz described the colors in FOC as Red, Green, and Blue; (4) Other colors also occur in FOC but they mainly result from color filling-in and mixing in parts of the afterimage - for example, Magenta from a surrounding ring would intrude into the central disk of Yellow to produce an orange color.
(1) The results are clearly more consistent with Young-Helmholtz's Trichromatic Theory than with OPT; (2) The fact of hue reversal implies that FOC occurs at a neural level instead of as some photochemical bleaching process; (3) Thus I suggest that there is a cortical, tetra-channel, complementary color system consisting of three chromatic pairs (Red-Cyan, Green-Magenta, and Yellow-Blue) and one achromatic pair (Black-White); (4) As afterimages are normally monocular, mapping onto the anatomical organization of human visual system, I suggest that layer 4C in primary visual cortex (V1) is the neural substrate for FOC in specific and afterimages in general; (5) I further propose, tentatively, that this neural substrate holds the mechanisms for color mixing, color filling-in, color transparency, and color complementarity observed in many color (including brightness) perceptual phenomena.
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