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Remy Allard, Patrick Cavanagh; Detection mechanisms selective to combinations of luminance- and contrast-modulations. Journal of Vision 2009;9(8):973. doi: 10.1167/9.8.973.
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First, we evaluated cross-attribute interactions by measuring detection thresholds for luminance- (LM) and contrast-modulated (CM) Gabor signals embedded in either LM or CM noise. As previously found (Allard and Faubert, VR 2007), masking was attribute-specific: detection thresholds for LM signal were greater in LM than CM noise and vice versa. This suggests independent mechanisms for these two attributes at the detection stage. We then investigated whether there are additional mechanisms that detect specific combinations of the two attributes by measuring detection thresholds when the two were combined in phase (LM+CM) or in counter-phase (LM−CM) and embedded in either LM+CM or LM−CM noise. When the signal and noise were defined by the same combination (both in phase, or both in counter-phase), detection thresholds were greater than when the signal and noise were defined by orthogonal combinations (e.g. in-phase signal, counter-phase noise). Furthermore, when the signal and noise were defined by orthogonal combinations, the detection thresholds were lower than the single attribute detection thresholds (e.g. LM signal, LM noise). Consequently, the combination of LM and CM attributes was detected even though both of the component attributes were subthreshold. This result implies that in addition to the independent LM and CM detection mechanisms, there must be others that respond to specific combinations of these attributes.
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