Seeing motion in depth using inter-ocular velocity differences

Abstract

An object moving in depth produces retinal images that change in position over time by different amounts in the two eyes. This allows stereoscopic perception of motion in depth to be based on either one or both of two different visual signals: inter-ocular velocity differences, and binocular disparity change over time. Disparity change over time can produce the perception of motion in depth. However, demonstrating the same for inter-ocular velocity differences has proved elusive because of the difficulty of isolating this cue from disparity change (the inverse can easily be done). No physiological data are available, and existing psychophysical data are inconclusive as to whether inter-ocular velocity differences are used in primate vision. Here, we use motion adaptation to assess the contribution of inter-ocular velocity differences to the perception of motion in depth. If inter-ocular velocity differences contribute to motion in depth, we would expect that discriminability of direction of motion in depth should be improved after adaptation to frontoparallel motion. This is because an inter-ocular velocity difference is a comparison between two monocular frontoparallel motion signals, and because frontoparallel speed discrimination improves after motion adaptation. We show that adapting to frontoparallel motion does improve both frontoparallel speed discrimination and motion-in-depth direction discrimination. No improvement would be expected if only disparity change over time contributes to motion in depth. Furthermore, we found that frontoparallel motion adaptation diminishes discrimination of both speed and direction of motion in depth in dynamic random dot stereograms, in which changing disparity is the only cue available. The results provide strong evidence that inter-ocular velocity differences contribute to the perception of motion in depth and thus that the human visual system contains mechanisms for detecting differences in velocity between the two eyes' retinal images.

Stereoscopic Viewing and Reported Perceived Immersion and Symptoms

“…18 -20 S3D viewing often entails tracking a visual object through space and depth, and binocular disparity provides critical visual cues for detecting motion in depth. 21,22 As such, stereoscopic viewing likely affords greater motion perception than 2D viewing and, hence, induces greater motion sickness symptoms due to a heightened conflict between vision and other senses.…”

Unresolved issues in stereopsis: dynamic disparity processing

“…This idea has been controversial. Fernandez and Farell (2005) showed that adapting to frontoparallel motion improved motion-in-depth direction discrimination, consistent with a role for interocular velocity differences in motion-in-depth perception. However, Harris et al (1998) found that targets moving in the z-axis did not pop out among stationary distractors, and concluded that the visual system is not sensitive to interocular motion differences.…”

Motion processing with two eyes in three dimensions

“…In addition to the changes in binocular disparity that result from these opposite retinal motions, visual percepts of 3D motion are in part determined by a mechanism that extracts interocular velocity differences (IOVDs) per se. Although there is an increasing body of evidence suggesting a strong and unique contribution of IOVDs (Brooks, 2002a(Brooks, , 2002bBrooks & Stone, 2004Czuba, Rokers, Huk, & Cormack, 2010;Fernandez & Farell, 2005;Rokers, Cormack, & Huk, 2008;Shioiri, Kakehi, Tashiro, & Yaguchi, 2009;Shioiri, Nakajima, Kakehi, & Yaguchi, 2008;Shioiri, Saisho, & Yaguchi, 2000), it is unclear how motion signals used to make this interocular comparison fit into the known visual hierarchy (Regan & Gray, 2009). We investigated whether the IOVD mechanism operated upon early stages of motion processing typically ascribed to primary visual cortex (V1), or on later stages of processing that extract the motions of patterns, which is typically ascribed to extrastriate areas like the middle temporal area (MT) and related motion processing structures (Khawaja, Tsui, & Pack, 2009;Movshon, Adelson, Gizzi, & Newsome, 1985;Perrone & Thiele, 2002;Simoncelli & Heeger, 1998).…”