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Michael Wagner, Ronen Hershman, Avishai Henik; Percept- driven versus data-driven pupil's response: effects of illusory depth.. Journal of Vision 2018;18(10):511. doi: https://doi.org/10.1167/18.10.511.
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Fixating spatial objects elicits synchronized visual processes such as accommodation, vergence and pupil response. Few studies such as Enright (1987), and Wagner et. al. (2009), indicated that vergence and pupil-response could be controlled by top-down processes. Fixating near objects in natural environments elicits pupil constriction, and far object fixation elicits pupil dilatation, these are the well-known pupil near-far responses, based on physiological physical processes. In the present study, we investigated the effects of illusory distance on the pupil dynamics. Our participants performed a detection task responding to "near" or "Far" targets, with proportional size and location to their background perspective illusory depth environment. During each trial participants performed eye-movements from central fixation towards the detected "near" or "Far" target. A fronto-parallel scrambled-image of the perspective surface served as 2-D control background for the identical targets during control trials. Eye-movements and pupil-size were measured with the EyeLink-1000 eye-tracker. Our results indicated significant differences of pupil response patterns, during detection task on the test- illusory control surfaces, as compared to the 2D control background. Our measured pupil size dynamic patterns towards illusory "near" or "Far" targets resembled the natural "near-far pupil reflex". Our data support the hypothesis of possible top-down: percept-driven control on pupil response. In an additional experiment, we could compare rapid ﬁxational eye movements with stable target fixations. Results here support the speculation on the existence of at least two eye movement systems: an automatic, data-driven system for rapid successions of ﬁxations, and a deliberate schema-driven system that accounts for stable ﬁxations based on the perceptual state of the observer.
Meeting abstract presented at VSS 2018
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