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Jeff Ferrucci, Peter Bex, Glen L McCormack; Motion sharpening processes in stereoscopic motion-in-depth. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5418.
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© ARVO (1962-2015); The Authors (2016-present)
Blurred images moving in stereoscopic depth are neurally sharpened more than laterally moving equally blurred binocular images having the same retinal image velocities. We examined whether asymmetric motion sharpening – a retinal process that sharpens the trailing edges of moving ocular images but not the leading edges – caused the difference between stereoscopic and lateral motion sharpening.
10 normally binocular young adults viewed images on an Asus 3D display. The test images were 1°w x 2°h bars of 50% contrast on a dark gray background, with 42’ edge blurs. The bars moved at velocities of 0.5°/s or 2.0°/s. Experiment 1: Monocular test bars appeared for 0.5 sec above or below a fixation cross, at random. To measure asymmetric motion sharpening, the leading edge of a test bar was matched to its 42’ trailing edge by a PEST staircase technique. Matches were obtained for all combinations of eye, motion direction, and velocity. Experiment 2: Binocular images, moving laterally or in stereoscopic depth, were constructed from the perceptually edge-matched ocular images derived from experiment 1, thus removing asymmetric sharpening. Moving test bar blur was then measured by matching its blur, via PEST, to an adjustable-blur static comparison bar on the opposite side of fixation. Experiment 3: Performed like experiment 2, but with test bars constructed from ocular images having physically equal 42’ left and right edge blurs.
Mixed ANOVAs evaluated the effects of motion direction, subject, eye, and velocity on match blur. Experiment 1: Leading edge blurs had to be reduced by 19.6% at 2°/s to match trailing edge blurs (F=92.5, p≤0.0001). Experiment 2: Stereoscopic motion sharpening was stronger than conjugate lateral motion sharpening at 2°/s (F=6.68, p=0.036). Experiment 3: Stereoscopic motion sharpening was again stronger than lateral motion sharpening at 2°/s (F=7.11, p=0.032). The relative strength of stereoscopic motion sharpening did not differ between experiments 2 & 3. (F=1.2, p=0.37).
(1) Asymmetric motion sharpening does occur with the type of stimuli we used. (2) Motion sharpening is stronger in stereoscopic motion-in-depth than in conjugate lateral motion, with or without edge-matched ocular images. (3) Stronger stereoscopic motion sharpening must be a property of a symmetric sharpening process in cortical stereoscopic motion-in-depth cells.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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