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| Paper IPM / Cognitive / 7489 |
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| Abstract: | |
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McCollough effect is an orientation-contingent color aftereffect in which adapting to differently colored gratings of different orientations produces negative color aftereffects contingent on bar orientation. In this study a modified McCollough effect (color-contingent orientation adaptation) was introduced in order to evaluate the interactions between orientation and color in unresolvable patterns. At first orientation selective adaptation was examined for unresolvable Gabor patches. Adapting stimulus was a peripheral Gabor patch whose spatial frequency was beyond the perceptual resolution limit. Test stimulus was a low contrast thin line with either the same (same adapt-test) or different (different adapt-test) orientation with respect to the adapting Gabor patch. Results showed that although subjects were unable to discriminate the adapting orientation (the performance was at chance level), they discriminated the orientation of different adapt-test more accurately than the orientation of same adapt-test. In the second experiment adaptation to colored (green or red) unresolvable Gabor patches was tested using low contrast colored resolvable Gabor patches as test stimuli. Results revealed that orientation selective adaptation existed only when the colors of adapting and test stimuli were identical (color-contingent orientation adaptation). According to these results the interaction between orientation and color occurs during the modified McCollough effect in probably V1 or higher cortical areas when subjects have no conscious access to the orientation of adapting stimulus
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