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S. Shimojo, Y. Kamitani; Fillin-in induced by high-contrast edge adaptation. Journal of Vision 2001;1(3):53. doi: 10.1167/1.3.53.
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© ARVO (1962-2015); The Authors (2016-present)
Purposes: We found that adaptation to an object with high contrast edges delays detection of a subsequent one with low contrast edges at the same location. During this delay the observer perceives only the background which is filled into the test region. We aimed to measure the effect as a function of adapting duration, and to determine if it should be attributed to the afterimage interfering/canceling the test, or rather to the failure of edge detection due to adaptation, which leads to filling-in. Methods: A white disk (42.0 cd/m2, 2.8 diameter) was presented at 4.8 deg. eccentricity on a gray background (17.3 cd/m2) for 2, 4, 8, or 16 sec. It was turned off briefly (93 ms) every 500 ms to minimize afterimage formation. Then, a slightly brighter gray disk (18.8 cd/m2) of the same size was presented at the same location. In a 10-sec test period, the subjects pressed a button as long as they saw the test disk, an afterimage, or both. In separate control experiments, they monitored visibility of (a) the afterimage on a homogeneous gray background, or (b)the test disk without adaptation. Results: (1)The total invisible time increased as a function of adapting duration, up to 6–7 sec (p < 0.02, 0 vs. 8 or 16 sec. adaptation). (2)An afterimage was visible (up to 4–5 sec with longer adaptation), yet shorter than the total invisible time in the main exp., at some or all durations in 4 of 5 observers. Discussion: The result (1) can not be explained by visible afterimage since by definition of the task, it would increase (or maintain the same duration of) button pressing. The result (2) is inconsistent with the idea that the test disk and the afterimage cancel each other, which would require the afterimage duration same as, or longer than, the invisible time. The effect may rather be related to failure of edge detection due to peripheral and/or cortical adaptation, which then leads to surface filling-in at a higher-level boundary-based representation.
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