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Elizabeth Fast, Koen Haak, Min Bao, Stephen A. Engel; Four days of visual contrast adaptation: effects on perceived contrast grow monotonically while effects on orientation rise then fall.. Journal of Vision 2014;14(10):400. doi: https://doi.org/10.1167/14.10.400.
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© ARVO (1962-2015); The Authors (2016-present)
The visual system continuously adapts to its environment. In contrast adaptation, exposure to high contrast patterns reduces the apparent contrast of similar patterns and shifts apparent orientation away from the adapter (the tilt-aftereffect). Most studies to date have examined only short periods of adaptation, generally a few minutes, so how perception changes over longer adapting periods remains unknown. Here we measured the effects of four days of adaptation to reduced contrast, which has similar effects to classic contrast adaptation, but in the opposite direction. Subjects wore a camera, whose video was filtered in real time and viewed on a head-mounted display. Filtering removed 85% of vertical energy from the images. Twelve subjects wore the display during their waking hours, and were blindfolded during rest breaks and at night. Perception was tested 4 times daily: To measure apparent contrast, subjects adjusted a horizontal grating patch to match the apparent contrast of a 5% vertical test. To measure the tilt-aftereffect, subjects adjusted the orientations of two 45 deg gratings, superimposed to make a plaid, until the plaid's intersections appeared square. The average perceived contrast of the 5% test rose during the first day to ~7.5%, and then continued to grow smoothly during the second through fourth days to end at ~8.5%, with a reliable linear trend (p <0.05). The tilt-aftereffect showed a different pattern; it rose to ~1.5 deg on the first day, and to ~2 deg on the second day, but fell on the third and fourth days to end near 1 deg, with a reliable quadratic trend (p <0.05). These results suggest that over many days of adaptation the visual system maintains effects that render the appearance of the world more natural, while correcting for effects, such as the tilt-aftereffect, that distort its appearance.
Meeting abstract presented at VSS 2014
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