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Lisa O'Kane, Pascal Mamassian; Temporal dynamics of the depth aftereffect. Journal of Vision 2004;4(8):487. doi: 10.1167/4.8.487.
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© ARVO (1962-2015); The Authors (2016-present)
Perceptual aftereffects have been traditionally studied using a nulling technique or by measuring duration. We are interested here in studying the full temporal dynamics of aftereffects with a novel technique. We apply this technique to the depth aftereffect. Participants adapted to a frontoparallel surface displayed in front of a fixation point for 30 seconds. The surface viewed was depicted by binocular disparities of random dots refreshed every half-second. Vergence was maintained using a surrounding texture with zero disparity. Following a brief interval, a similar surface was presented for 30 seconds at a disparity chosen differently from trial to trial. During this test phase, participants were asked to judge the perceived depth (in front or behind) of the surface at the sound of a beep presented on average every 2 seconds. Repeating these sequences of adaptation and test phases allowed us to measure the dynamics of the aftereffect for different test depths. We found that the dynamics of the aftereffect depended on the disparity of the test surface. As predicted, the smaller the disparity of the test, the longer the aftereffect lasted. The time constant of the aftereffect was defined as the time needed to reach the point of subjective equality (where percepts are equally distributed in front and behind fixation). These time constants increased as the test disparity decreased, even beyond the critical disparity that produced a consistent initial aftereffect. In summary, we have proposed an original method to investigate the temporal dynamics of perceptual aftereffects. Unlike the nulling technique, our paradigm allowed us to measure the full temporal variation of the aftereffect. In addition, our method is more objective than the traditional technique of estimating the end of the aftereffect.
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