The Journal of Neurophysiology Vol. 84 No. 6 December 2000, pp. 3078-3082
Copyright ©2000 by the American Physiological Society

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Central Versus Peripheral Origin of Vestibuloocular Reflex Recovery Following Semicircular Canal Plugging in Rhesus Monkeys

 ¹Department of Neurology, University Hospital Zurich, CH-8091 Zurich, Switzerland;  ²Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, Illinois 60612;  ³Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Maryland 21287; and  ⁴Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110

Hess, Bernhard J. M., Anna Lysakowski, Lloyd B. Minor, and Dora E. Angelaki. Central Versus Peripheral Origin of Vestibuloocular Reflex Recovery Following Semicircular Canal Plugging in Rhesus Monkeys. J. Neurophysiol. 84: 3078-3082, 2000. We have previously shown that there is a slowly progressing, frequency-specific recovery of the gain and phase of the horizontal vestibuloocular reflex (VOR) in rhesus monkeys following plugging of the lateral semicircular canals. The adapted VOR response exhibited both dynamic and spatial characteristics that were distinctly different from responses in intact animals. To discriminate between adaptation or recovery of central versus peripheral origin, we have tested the recovered vestibuloocular responses in three rhesus monkeys in which either one or both coplanar pairs of vertical semicircular canals had been plugged previously by occluding the remaining semicircular canals in a second plugging operation. We measured the spatial tuning of the VOR in two or three different mutually orthogonal planes in response to sinusoidal oscillations (1.1 Hz, ±5°, ±35°/s) over a period of 2-3 and 12-14 mo after each operation. Apart from a significant recovery of the torsional/vertical VOR following the first operation we found that these recovered responses were preserved following the second operation, whereas the responses from the newly operated semicircular canals disappeared acutely as expected. In the follow-up period of up to 3 mo after the second operation, responses from the last operated canals showed recovery in two of three animals, whereas the previously recovered responses persisted. The results suggest that VOR recovery following plugging may depend on a regained residual sensitivity of the plugged semicircular canals to angular head acceleration.