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Takao Sato, Yutaka Nakajima; Orientation and shape tuning of van Lier aftereffect. Journal of Vision 2010;10(7):1392. doi: https://doi.org/10.1167/10.7.1392.
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© ARVO (1962-2015); The Authors (2016-present)
van Lier et al(2009, Current Biology) have reported an intriguing color aftereffect. They adapted observers with two differently colored, overlapping four-point stars sharing the center, but with a 45 deg relative rotation, and subsequently presented achromatic test outline of one of the stars. Perceived afterimage was stronger inside the test, and the color of aftereffect inside the test pattern extended to the central area where it was colored gray in adaptation phase. In the present study, we tried to evaluate orientation and shape selectivity of the phenomenon by using almost the same stimuli as they used. For orientation tuning, the test pattern was rotated relative to the up-right adaptor. The original phenomenon was reproduced when the adaptor and test overlapped exactly, but most observers see afterimage only within the test contour pattern. Afterimage was switched on and off altogether depending on test orientation. Similar afterimage was observed up to 15 deg of rotation, when the test pattern was rotated. Observers perceived a color afterimage including the central area that corresponds to the adaptor with nearer orientation. In addition, the after images in rotated conditions did not exactly fill-in the test contour, but it had original up-right orientation with discrepancy to the rotated test contours. For shape tuning, the base width of the stars was manipulated, and similar after effects were observed up to 20% to the fatter side and more than 50% to the thinner side variations of the width of the test contour. Here again, discrepancies between afterimage and test contour similar to those found for rotation was observed. The afterimages were either thinner or fatter than test contour depending of the width relationship between adaptor and test. These results indicate that switching colors and spatial filling-in are mediated by separate mechanisms.
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