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Scott B Stevenson, Archana Bora, Maria M Nilsson, Rune L Brautaset; Cyclovergence is controlled by both interocular correlation and interocular velocity difference mechanisms.. Journal of Vision 2012;12(9):43. doi: 10.1167/12.9.43.
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© ARVO (1962-2015); The Authors (2016-present)
Eye alignment is controlled visually on horizontal, vertical, and torsional axes. Torsional alignment depends specifically on vertical disparity of opposite sign in the left and right hemifields. Previous studies used static patterns with changing disparity, which include both interocular correlation (IOC) and interocular velocity difference (IOVD) information. We tested the effectiveness of each for driving cyclovergence. Method: Three human subjects wearing scleral search coils and anaglyph glasses viewed a 76 degree diameter circular field of 1000 random dots. The IOC stimuli contained the same random dot pattern in each eye (100% correlation). Dots were replaced in each frame (60Hz), to remove monocular motion information. The IOVD stimuli contained a different random dot pattern in each eye (0% correlation). Dots were unchanged throughout the trial so that monocular motions were visible. Cyclo disparity for both stimuli was sinusoidally modulated (0.33 Hz, peak velocity 10 deg/sec). IOVD was also tested with 30 and 90 deg/sec stimuli. The response measure was the amplitude of cyclovergence at 0.33 Hz. Results: Both classes of stimuli were effective in driving cyclovergence. Responses to IOC stimuli had gains ranging from 0.1 to 0.2, consistent with previous reports using static patterns. Responses to IOVD stimuli were weaker, with gains of .05 to .15 at 10 deg/sec. Higher velocity stimuli did not increase response amplitude appreciably, so the slowest stimulus tested had the highest gains. Conclusions: Responses to the IOC stimuli establish that cyclovergence can be driven by a correlation based disparity mechanism in the absence of monocular motion information. Responses to the IOVD stimuli establish that cyclovergence can also be driven by opposed monocular motions in the absence of interocular correlation. These results extend findings from psychophysical studies of horizontal disparity, establishing that these two mechanisms also serve reflexive eye alignment control.
Meeting abstract presented at VSS 2012
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