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Xiaohua Zhuang, Steven K. Shevell; Plaid from orthogonal rivalrous gratings: Binocular resolution of competing neural representations. Journal of Vision 2020;20(11):221. doi: https://doi.org/10.1167/jov.20.11.221.
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© ARVO (1962-2015); The Authors (2016-present)
Monocular presentation of alternating orthogonal gratings at a frequency above critical fusion gives the percept of a plaid. Recent studies of interocular-switch rivalry (ISR) show that a plaid percept occurs at a much lower temporal frequency. The question addressed here is whether the plaid perceived using ISR is caused by reduction of contrast sensitivity in the magnocellular (MC) pathway, which then reduces interocular suppression, leading to binocular superposition.
Methods: In Experiment I, orthogonally oriented luminance gratings were presented to the two eyes in three conditions: (1) standard binocular rivalry (SBR) condition, in which each eye saw only one of the two gratings during an entire 10-second trial; (2) interocular-switch rivalry (ISR) condition, in which the orthogonal gratings were swapped between the two eyes every 160 msec (3.13 Hz) during a trial; or (3) binocular non-rivalrous viewing (NR) condition, in which both eyes saw the same grating at any given moment, with the grating alternating between two orthogonal orientations every 160 msec. In Experiment II, prior adaptation to 10-Hz full field luminance flicker was added before each trial to desensitize the MC pathway and thereby assess the role of MC contrast sensitivity in perceiving binocular plaid.
Results and conclusions: Plaid was observed more often in the ISR condition than in other conditions. Thus, swapping the orthogonal stimuli between the two eyes facilitated the appearance of plaid. Plaid was rare in the NR condition, eliminating the possibility that plaid was caused by superposition of a monocular grating with an afterimage of the most-recently-extinguished grating. Adaptation to luminance flicker did not significantly alter the perception of plaid. These results are consistent with the hypothesis that transient swapped stimuli with ISR are sufficient to reduce interocular suppression, thereby achieving binocular superposition, assuming very rapid MC recovery from preceding flicker adaptation.
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