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Eiji Kimura, Ken Goryo; Differential effects of interocular suppression on the pupillary constriction and dilation. Journal of Vision 2016;16(12):1215. doi: 10.1167/16.12.1215.
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© 2017 Association for Research in Vision and Ophthalmology.
This study produced different perceptual changes using physically-identical binocularly-rivalrous stimulus sequences and investigated the effects of interocular suppression on the pupillary response. When a white and a black disk were presented at the same retinal position of different eyes, binocular rivalry can be experienced. We asked observers to press a key when one of the disks (e.g., black disk) became exclusively dominant. Then just after the key press, we switched the dichoptic stimuli to binocular white disks (WW condition) or binocular black disks (BB condition). Depending on the initial dominant percept, the stimulus sequence produced different perceptual changes. For example, when the initial percept was black, a black-to-white perceptual change was produced in the WW condition. However, in the same WW condition, a white-to-white change was produced when the initial percept was white. We measured the pupillary response during these stimulus sequences. Results showed that the direction of the pupillary response was determined by the physical stimulus change; i.e., the pupil constricted to the stimulus change in the WW condition, whereas it dilated in the BB condition. However, the constriction and dilation amplitudes were modulated in conjunction with the perceptual change in brightness. In the WW condition, the constriction was larger when the perceptual change was black to white than when it was white to white. Similarly in the BB condition, the dilation was larger when the perceptual change was white to black. Moreover, the modulating effect of interocular suppression was more consistent on the dilation; i.e., significant modulation was found for all observers in the dilation, but for 8 of 12 observers in the constriction. These results indicate that the pupillary dilation is a more reliable measure of interocular suppression and may suggest that interocular suppression differentially affects the pupillary pathways mediating the constriction and the dilation.
Meeting abstract presented at VSS 2016
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