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David P. Crewther, Anita Panayiotou; Multistable motion rivalry - four co-localised motion directions compete with similar dynamics to binocular motion rivalry. Journal of Vision 2005;5(8):14. doi: 10.1167/5.8.14.
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© ARVO (1962-2015); The Authors (2016-present)
Following Diaz-Caneja's observation of multistable perception across the midline, Suzuki and Grabowecky (Neuron 2002) have recently studied the dynamics afforded by the increased perceptual options, including path dependence and on-line adaptation, which were equivalent whether the rivalrous exchanges perceived were formed by single-eye or mixed-eye dominance. Because the four perceptual options of Suzuki were formed by a mid-line split of the two stimuli, we investigated whether more than two discrete stimuli existing at the one point in space could individually compete for dominance. Three experienced subjects with normal or corrected-to-normal vision viewed through a stereoscope (or performed free-fusion of) two circular stimuli each containing a red pattern of moving dots and a green pattern moving in the opposite direction (Left eye Up-Down, right eye Left-Right), each with 90% coherence. Thus all four cardinal directions are represented when the patterns are superimposed. After a short period of adjustment, alternation of 4 rivalrous percepts emerged such that alternations of dominant motions were clearly visible with other motions either missing or apparently in the background. Each of the four motions demonstrated dominance durations well-fit by a log-normal distribution. Mean durations were calculated for a series of trials where the velocity of one dot motion (green horiozontal) was varied from 1 to 40°/sec. While interaction was clear between dominance durations for opposite motions, increasing the strength of one direction did not appear to affect durations of orthogonal directions. Transition history showed that approximately 55% of transitions were within eye and 45% between eyes, despite and equal probability model predicting 33.3% within eye and 66.7% between eye. Both interocular rivalry suppression and hemispheric switching theories would require significant modification in order to explain the data.
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