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Mick Falconbridge, Ladan Shams, Stephen Engel; Adaptation can increase sensitivity to visual features. Journal of Vision 2007;7(9):356. doi: 10.1167/7.9.356.
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In adults, prolonged exposure to simple visual features usually reduces sensitivity to the exposed feature. During development, however, long-term exposure to visual features increases or maintains sensitivity to the exposed features. Here, we show that prolonged exposure to a relatively simple novel feature can increase sensitivity in adult humans. Subjects viewed images that had been manipulated to introduce a second-order visual feature, a consistent correlation between particular local image elements. Wherever an image contained local energy at a specified orientation (135 degrees), phase (0), and spatial frequency (4 cycles/deg.), we added an equal amount of local energy with the same characteristics at a constant spatial offset (0.5 deg. down and to the left). These manipulations were performed on frames taken from a popular television show. Subjects passively viewed 42 minutes of the altered video (accompanied with original soundtrack). Prior to and following viewing, subjects performed a contrast matching task. This allowed us to measure the apparent contrast of a target grating patch with the same orientation and spatial frequency as in the second order feature. Subjects matched the patch presented alone, or in the presence of a flanking patch. The flanker had the same spatial offset as that used to create the second order feature, and its orientation either matched that of the target, thus precisely reproducing the configuration of the second order feature, or was orthogonal to it. Exposure to the altered videos reliably increased the apparent contrast of the target grating. The increase occurred only when the target/flanker configuration matched the second-order feature added to the video. Subjects that viewed an unaltered video showed no effects of exposure. Our results suggest that adaptation can increase sensitivity to novel low level visual features. The visual system may modify its encoding of features to reflect the statistics of the environment.
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