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Alexandre Reynaud, Robert Hess; A contrast-based Pulfrich effect in normals and a spontaneous Pulfrich effect in amblyopes. Journal of Vision 2017;17(10):155. doi: https://doi.org/10.1167/17.10.155.
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Any processing delay between the two eyes can result in illusory 3D percepts for moving objects because of either changes in the pure disparities over time for disparity sensors or by changes to sensors that encode motion/disparity conjointly. This is demonstrated by viewing a fronto-parallel pendulum through a neutral density (ND) filter placed over one eye, resulting in the illusory 3D percept of the pendulum following an elliptical orbit in depth, the so-called Pulfrich phenomenon. Because of the difference between their two eyes, a small percentage (4%) of mild anisometropic amblyopes who have rudimentary stereo are known to experience a spontaneous Pulfrich phenomenon. Here we use a paradigm where a cylinder rotating in depth, defined by moving Gabor patches is presented at different interocular phases, generating strong to ambiguous depth percepts. This paradigm allows one to manipulate independently the spatio-temporal properties of the patches to determine their influence on perceived motion-in-depth. We show psychophysically that an interocular contrast difference can itself result in a similar illusory 3D percept of motion-in-depth. For amblyopes we observe a spontaneous Pulfrich phenomenon but opposite to that expected, suggesting a faster processing by the amblyopic eye. This spontaneous delay is reduced at low spatial and temporal frequencies. We conclude that spatio temporal properties of the stimuli are important for the illusion of motion-in-depth from contrast differences or the spontaneous Pulfrich experienced by some amblyopes.
Meeting abstract presented at VSS 2017
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