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Kai-Markus Mueller, David H. Do, David A. Leopold; Independent measures of adaptation and aftereffect. Journal of Vision 2008;8(6):73. doi: 10.1167/8.6.73.
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© ARVO (1962-2015); The Authors (2016-present)
Visual aftereffects are common research tools in psychophysics. A major rationale underlying this research is that the visual system recalibrates during adaptation, e.g. through inhibition or through shifting the norm. This idea can be traced back to Gibson (1933) who investigated adaptation to a curved line. His subjects reported (1) “adaptation” (subjective straightening of the curvature over time) and (2) negative aftereffect (appearance of opposite curvature in a subsequently presented straight line). Here we explored the relationship between these two phenomena, particularly the dynamic perceptual changes associated with the adaptation effect. The subtle adaptation effect is difficult to measure using traditional psychophysical approaches. Accordingly experiments have almost exclusively concentrated on the subsequent aftereffect, which can be studied objectively using nulling or forced choice procedures. Here we present a new psychophysical approach that allows us to investigate directly dynamic aspects of the process of adaptation. Subjects adapted to a curved line and reported curl motion - either curling or uncurling. By applying subthreshold curling movement to the line and using a staircase procedure, we were able to cancel the subjects' perceived straightening of the line. We measured the extent of adaptation using both this dynamic nulling technique, as well as classical static nulling of the subsequent aftereffect to a briefly presented pattern. Both techniques provided a robust measure of curvature adaptation. Interestingly, in neither technique did the level of adapting curvature in the tested range affect the magnitude of the effect. Although the two techniques provided similar mean trends, magnitudes of adaptation and aftereffect across subjects did not correlate. Our approach of dynamic nulling of subjective adaptation provides an effective tool to probe dynamics of visual adaptation during the adaptation phase itself.
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