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Robert Geary, Howard Ying, Kristina Irsch; Quick phase of the torsion vestibulo-ocular reflex increases the gain of the slow phase both before and after the quick phase. Invest. Ophthalmol. Vis. Sci. 2013;54(15):181.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize the slow phase of the torsion vestibulo-ocular reflex (tVOR) with respect to quick phases using high speed video-oculography (VOG).
Four normal volunteers were tested. TVOR with the eyes in the straight ahead position was stimulated by 10°-40° rotations at 0.1-1.0 Hz in the roll plane using a 6 degree of freedom (DOF) motion platform (MOOG Inc., East Aurora, NY) or using active quasi-sinusoidal head rotations. Targets were a head-mounted laser directed straight ahead on a distant detailed visual scene or a rotating optokinetic nystagmus (OKN) stimulus 10 cm in front of the subject with angular rotation of 30-60 °/s. 3-D eye movements were recorded using VOG goggles (RealEyes xDVR, Micromedical Tech., Chatham, IL) driven at 130 Hz or using scleral search coils recording at 1 kHz. Head movement was recorded using a 3DOF orientation tracker (MTx , Xsens, Los Angeles, CA). Recordings were processed using Matlab (Mathworks, Natick, MA) and Iris Tracker (Chronos Vision, Berlin, Germany).
Subjects showed ocular torsion rotation contraversive to active head rotation, slow phase of the tVOR with average gain with respect to head rotation of 0.69 ± 0.17 for active head roll. Slow phase velocity was proportional to head velocity, as expected. Interestingly, slow phase velocity was also proportional to quick phase amplitude. Moreover, the slow phase velocity was increased closer to the quick phase, whether it was before or after it. Corresponding tVOR gain was increased soon after the quick phase. Interestingly, slow phase gains were also increased preceding the quick phase.
Together, these results suggest that the tVOR slow phases with near unity gain are pre-programmed before the start of the corresponding quick phase.
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