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Chien-Chung Chen; The interaction between flanker phase and position in lateral masking. Journal of Vision 2011;11(11):1176. doi: 10.1167/11.11.1176.
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© ARVO (1962-2015); The Authors (2016-present)
The visibility of a target stimulus can be affected by the presence of other stimuli (flankers) projected onto different parts of the retina. Previous studies showed that the greatest lateral facilitation effect occurs when the flanker has the same orientation, phase as the target and at the collinear position. Here, we show that there is an interaction between the flanker phase and position in lateral interaction. The task of our three observers was to detect a 4 cy/deg vertical Gabor target in the presence of vertical flanker Gabors. The target was in sine phase related to the fixation. The flankers had either the same or the opposite phase from the flanker. Flanker locations were either 0 (collinear), or 90 deg (side) away from the collinear axis. The distance between the flankers and the target varied from 1 to 7.5 wavelengths. The flanker contrast was 50%. We measured target thresholds with a 2AFC paradigm and a PSI staircase method at 75% correct response level. Compared with the no-flanker condition, the collinear flankers significantly decreased target threshold only if the flanker was in the same phase as the target. The collinear opposite phase flanker showed little, if any, effect. The opposite phase side flanker significantly decreased target threshold while the same phase side flanker did not. That is, the phase effect for the collinear flanker was opposite from that of the side flankers. The side flanker has an effect only if the bright region of the target links to the bight region of the flanker, and the dark region to the dark. This result may be consistent with the notion of the border ownership in which facilitation occurs when the target and the flankers signal the two opposite border of the same surface.
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