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Jawshan Ara, Solena Mednicoff, Michael Webster; Adaptation and compensation in anomalous trichromacy. Journal of Vision 2015;15(12):405. doi: 10.1167/15.12.405.
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© ARVO (1962-2015); The Authors (2016-present)
Anomalous trichromats have two similar longer wave pigments and thus reduced sensitivity to the reddish-greenish chromaticities carried by their differences. However, a number of studies have found that in some anomalous observers the salience of these hues is much greater than predicted by their sensitivity losses, consistent with a compensatory mechanism that tends to normalize the gamut of their perceptual color space. We explored the possibility that this could result in part from normal processes of contrast adaptation, by examining how normal trichromats would adapt to the reduced range of color signals available to color deficient observers. Images were 1/f noise with perceptually equated random variations in luminance and chromatic (S and LM) contrast. These images were then filtered with the spectral sensitivities of a deuteranomalous observer, and were adjusted for von Kries adaptation so that the mean chromaticity remained gray. Chromatic variations in the resulting images varied primarily in S-cone contrasts. Observers adapted to a rapid sequence of the filtered images shown in a 4-deg field for 5 minutes, and then interleaved with briefly presented test stimuli shown in the same field. The test images had the same luminance contrast but a fixed chromaticity spanning the S vs LM space at 22.5 deg intervals. The hue of the test was matched by adjusting the hue angle of a comparison image presented in an unadapted field to the other side of fixation. Adaptation to the biased chromatic contrasts in the anomalous images produced systematic biases in the perceived hue of the test images, consistent with a selective loss in sensitivity to the adapting colors. Our results suggest that in anomalous trichromats the losses in color contrast may lead to selective contrast adaptation which may act to rebalance and thus partly discount their sensitivity losses from their phenomenal color percepts.
Meeting abstract presented at VSS 2015
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