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Goro Maehara, Pi-Chun Huang, Robert F. Hess; The effect of flankers on TvC functions in binocular, monocular, and dichoptic presentations. Journal of Vision 2008;8(17):68. doi: https://doi.org/10.1167/8.17.68.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: We investigated how two co-aligned adjacent stimuli (flankers) influence threshold versus pedestal contrast (TvC) functions in binocular, monocular, and dichoptic presentations.
Methods: Targets were presented to the two eyes or to only one eye. Pedestals and flankers were presented to the same eyes to which targets were presented (binocular or monocular presentations) or to the different eyes (dichoptic presentation). All stimuli were Gaussian-windowed vertical sine-wave gratings. The spatial frequency of the sine-wave gratings and the standard deviation of the Gaussian function were 2c/deg.
Results and Discussion: In the binocular presentation, binocular flankers lowered thresholds at low and intermediate pedestal contrasts. We found similar flanker effects also in the monocular presentation. But the flanker effects almost disappeared when flankers were dichoptically presented. In the dichoptic presentation of targets and pedestals, flankers lowered thresholds when flankers were presented to the eye where targets were presented. In contrast, dichoptic flankers elevated thresholds at intermediate pedestal contrasts when pedestals were also dichoptically presented. These results suggest that flankers affect luminance contrast processing before binocular integration. We fitted binocular divisive gain control models to the data. Most of the results can be accounted for by assuming that flankers multiplicatively modulate sensitivity of linear filters at the monocular processing stage.
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