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Howard S. Ying, Robert B. Geary, Kristina Irsch; Visual And Post-saccadic Potentiation Of Ocular Counter Roll Gain Results In Near-stabilization Of Retinal Images. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4871.
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To characterize visual and post-saccadic potentiation of the torsion vestibulo-ocular reflex (tVOR) using high-speed video-oculography (VOG).
Three normal volunteers were tested. TVOR with the eyes in the straight ahead position was stimulated by 10 degree rotations at 0.1, 0.2, or 0.4 Hz in the roll plane using a 6 DOF motion platform (MOOG Inc., East Aurora, NY) or during active quasi-sinusoidal head oscillations in the roll plane with +/- 45 degree amplitude, 0.4 Hz. Target was a head-mounted laser light directed straight ahead on a detailed visual scene 3.5 meters in the distance and parallel to earth horizontal. 3-D eye movements were recorded using VOG goggles (Real Eyes xDVR, Micromedical Tech., Chatham, IL) driven at 130 Hz. Head movement was recorded using a 9 DOF motion sensor (MTi , XSens, Los Angeles, CA). Recordings were processed using Matlab (Mathworks, Natick, MA) and Iris (Chronos Vision, Berlin, Germany).
Subjects showed ocular torsion rotation contraversive to head rotation as expected at 0.1 Hz frequency. At 0.2 Hz, head velocity 12.81 +/- 0.79 degrees/sec, subjects showed saccades ipsiversive to head rotation and post-saccadic potentiation of counter roll gain to 0.64. At 0.4 Hz, head velocity 23.47 +/- 0.76 degrees/sec, subjects showed larger and more regular saccades ipsiversive to head rotation and post-saccadic potentiation of counter roll gain to 0.80. Active head rotation, +/- 45 degree amplitude, 0.4 Hz, did not appear to increase counter roll gain compared with passive head rotation using the motion platform.
Ocular counter roll gains of up to 0.8 were measured using our custom high-speed VOG system. This gain is significantly higher than previously reported values. During our experiments, visual feedback and higher head velocities were allowed, causing ipsiversive saccades. Saccadic potentiation and visual feedback appear to increase ocular counter roll gain so that the retinal image is nearly stabilized during the immediate post-saccadic interval.
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