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Clemente Paz-Filgueira, Michael R. Tan, Dingcai Cao; Dynamic of ON and OFF chromatic adaptation. Journal of Vision 2019;19(10):70a. doi: https://doi.org/10.1167/19.10.70a.
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Introduction: Zaidi et al (Current Biology, 2012) devised a time varying chromatic adaptation paradigm that used two hemifields modulating in opposite (ON and OFF) directions in cardinal axes. The present study assessed the dynamics of ON and OFF chromatic adaptation separately under different background chromaticities and identified which process determined the dynamics of adaptation with simultaneous ON and OFF modulations. Methods: Two stimulus types were used: one consisted of two hemifields (subtending 3.6°) complementarily modulated to opposite ends of a cardinal axis (simultaneous ON/OFF) and the other was only one of the two hemi-fields modulated along one end (either ON or OFF) of a given cardinal axis (L+M-, l=L/(L+M)- and s=S/(L+M)-axis). Modulation was half a cycle of a sinusoid (1/32Hz), starting and finishing on the mean background chromaticity. Nine backgrounds (20cd/m2) were set: one achromatic (EEW), 2 reddish (+l), 2 greenish (−l), 2 bluish (+s) and 2 yellowish (−s). The task was to report the time to reach the identity point, that is, when the stimulus had the same color as the background. Results: Compared with the ON stimuli, the time at the identity point occurrence for the OFF stimuli was shorter in the L+M and s directions, particularly with the EEW, bluish and yellowish backgrounds. Relative to the EEW background, the identity times with complementary modulations in the s-axis was decreased by the yellowish backgrounds and increased by the bluish backgrounds. Finally, the identity times with complementary modulations were equal or larger than the slower mechanism tested separately for the ON and OFF stimuli for all backgrounds. Conclusions: The ON and OFF adaptations in the L+M and s directions have different dynamics and the slower mechanism determined adaptation with simultaneous ON and OFF modulations.
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