Abstract
Interocular grouping (IOG) is a binocular visual function that can arise during multi-stable perception. IOG perception was initiated using split-grating stimuli constructed from luminance (L), luminance-modulated noise (LM) and contrast-modulated noise (CM). In Experiment 1, three different visibility levels were used for L and LM (or first-order) stimuli, and compared to fixed-visibility CM (or second-order) stimuli. Eight binocularly normal participants indicated whether they perceived full horizontal or vertical gratings, superimposition, or other (piecemeal and eye-of-origin) percepts. CM stimuli rarely generated full IOG, but predominantly generated superimposition. In Experiment 2, Levelt’s modified laws were tested for IOG in nine participants. Split-gratings presented to each eye contained different visibility LM gratings, or LM and CM gratings. The results for the LM-vs-LM conditions mostly followed the predictions of Levelt’s modified laws, whereas the results for the LM-vs-CM conditions did not. Counterintuitively, when high-visibility LM and low-visibility CM split-gratings were used, high-visibility LM components did not predominate IOG perception. Our findings suggest that higher proportions of superimposition during CM-vs-CM viewing are due to binocular combination, rather than mutual inhibition. It implies that IOG percepts are more likely to be mediated at an earlier monocular, rather than a binocular stage. Our previously proposed conceptual framework for conventional binocular rivalry, which includes asymmetric feedback, visual saliency, or a combination of both (Skerswetat et al. Sci Rep 8:14432, 2018), might also account for IOG. We speculate that opponency neurons might mediate coherent percepts when dissimilar information separately enters the eyes.
Highlights
Interocular grouping (IOG) is a binocular visual function that can arise during multi-stable perception
Data were analysed according to stimulus type (L, luminancemodulated noise (LM) and contrast-modulated noise (CM)), stimulus visibility and perceptual state
As there were different numbers of visibility levels for L and LM, versus CM stimuli, a repeated measures ANOVA analysis was first used to compare results for visible L, LM and CM stimulus types, and a separate analysis was used to compare across visibility levels for the first-order stimulus type
Summary
Interocular grouping (IOG) is a binocular visual function that can arise during multi-stable perception. Our findings suggest that higher proportions of superimposition during CM-vs-CM viewing are due to binocular combination, rather than mutual inhibition It implies that IOG percepts are more likely to be mediated at an earlier monocular, rather than a binocular stage. Significant physical differences between two monocular images can lead to exclusive visibility of one eye’s input for a few seconds until that eye’s input is suppressed, as the formerly suppressed eye’s input takes over visual awareness. This phenomenon is known as binocular rivalry[2,3,4,5]. These studies often used achromatic grating stimuli, defined by luminance changes, or stimuli with colour differences
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