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D. Yang, R.W. Hertle, V. Hill, R. Shatnawi; Vertical Optokinetic Nystagmus (OKN) and Binocular Motion Rivalry: Role of OKN Internal Gain . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2327.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: It has been shown that vertical OKN elicited by upward movement has a higher gain than downward elicited OKN. When two separate vertical OKN stimuli are presented dichoptically in opposite directions, binocular motion rivalry is stimulated. This results in alternating upward and downward vertical OKN eye movements. Little is known about the mechanisms that drive the alternating direction of these vertical eye movements during rivalrous stimuli. We hypothesize that the upward dominance will occur during binocular motion rivalry if the inherent asymmetry in vertical OKN gain plays an important role in the control of binocular motion rivalry. Methods: Monocular upward or downward OKN, and binocular upward/downward alternating OKN were recorded in 3 normal adult subjects using the infrared eye tracking technique. The Binocular rivalry motion stimuli displayed on CRT monitors in a Wheatstone stereoscope, subtended 44 degrees horizontally and 36 degrees vertically, and consisted of black–and–white stripes with a spatial frequency of 1.33 cyc/deg, and moved vertically at 10 to 27.5 deg/s. Subjects were instructed to look straight ahead and to maintain optically clear images. The time of upward and downward OKN eye movements was measured and normalized. Results: Monocular vertical OKN gain was higher during upward OKN stimuli (0.8) rather than during downward OKN stimuli (0.6). Vertical OKN gain for each eye (monocular gain) was equal between all right and left eyes. Binocular rivalrous stimuli resulted in the upward OKN response dominating over the downward OKN response. This dominance was more apparent and visible at higher temporal frequencies (from 63% vs 37% at 13 Hz to 69% vs 31 % at 26 Hz). Conclusions: The inherent asymmetry of the internal vertical OKN gain may play an important role in the control of binocular motion rivalry.
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