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Martin Lages, Alexander Dolia, Erich W Graf; Dichoptic motion within Panum's fusional area?. Journal of Vision 2003;3(9):798. doi: 10.1167/3.9.798.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose. Recent computational and neurophysiological findings suggest the existence of binocular complex cells that jointly encode motion and stereoscopic depth. Dichoptically presented gratings flickering in spatio-temporal quadrature can induce directional motion perception but the existence of an early binocular motion system is a debated issue. Here we investigated perception of dichoptic motion for stimuli defined on different depth planes.
Methods. Stimuli were presented to the left and right eye on a calibrated CRT display with a refresh rate of 120 Hz using a split-screen Wheatstone configuration. On each trial Ss verged on a fixation-cross flanked by nonius lines before two vertical sine-wave gratings of 1.1 c/deg were presented in dichoptic view. The gratings were displayed in a circular aperture for 200 msec flickering in temporal quadrature. After each presentation Ss indicated whether direction of motion was left or right. In three conditions disparity of the stimulus was set to −8, 0, or +8 arc min whereas spatial phase offset between gratings varied between pi/2 and 3pi/2 in randomly intermixed trials. Spatial and temporal phase of the gratings were randomised across trials.
Results. Although stimuli appeared on different depth planes psychometric functions shifted systematically with disparity. Discrimination of motion direction was best when phase offset together with horizontal disparity resulted in spatial quadrature. No reliable discrimination performance was obtained for stimuli with static pedestal, flicker frequencies beyond 4 Hz, and disparities outside Panum's fusional area.
Conclusions. The present result does not support the notion of an early binocular motion system that can integrate dichoptic motion at different depth planes.
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