Presented as a Candidate's Thesis (s.d.n.) to the Triological Society, Inc.
Relationship of Static and Dynamic Mechanisms in Vestibuloocular Reflex Compensation†
Article first published online: 3 JAN 2009
Copyright © 2005 The Triological Society
Volume 115, Issue 2, pages 191–204, February 2005
How to Cite
Newlands, S. D., Dara, S. and Kaufman, G. D. (2005), Relationship of Static and Dynamic Mechanisms in Vestibuloocular Reflex Compensation. The Laryngoscope, 115: 191–204. doi: 10.1097/01.mlg.0000154718.80594.2e
Supported by NIH grants DC K08 000182 and DC R01 004170.
- Issue published online: 3 JAN 2009
- Article first published online: 3 JAN 2009
- Manuscript Accepted: 28 JUN 2004
- Semicircular canals;
- vestibuloocular reflex;
Objectives/Hypothesis: We tested the hypothesis that recovery of dynamic oculomotor behavior (specifically the vestibuloocular reflex [VOR]) after a unilateral labyrinthectomy (UL) is independent from static deficit recovery (e.g., spontaneous nystagmus). This hypothesis predicts that VOR recovery from peripheral vestibular lesions that do not cause static symptoms, such as unilateral semicircular canal plugging (UCP), would have a similar time course and magnitude as recovery from a lesion that creates both a static and dynamic imbalance, such as UL. Furthermore, animals compensated after UCP would be expected to retain their compensated VOR response after the additional insult of ipsilateral labyrinthectomy.
Study Design: An experimental study in the Mongolian gerbil animal model.
Methods: The horizontal VOR was measured from both eyes using infrared video-oculography on gerbils before and after UCP, UL, or ipsilateral labyrinthectomy after a previous UCP. Eye movements were recorded during yaw rotation in the dark.
Results: UL resulted in a more severe acute deficit than the UCP. Over several weeks, the UCP animals compensated their horizontal VOR, particularly on rotation toward the intact side, quicker and more completely than the UL animals. Animals that underwent ipsilateral labyrinthectomy 8 to 11 weeks after UCP demonstrated preservation of the improved gain, particularly on rotation toward the intact labyrinth. However, the difference between the UL groups with or without precedent UCP was not retained after 72 hours, and long-term compensation was poorest in the UL after UCP group.
Conclusions: Plasticity in dynamic vestibular reflexes induced by UCP is preserved after a subsequent UL. However, neurologic events during the first and second day after UL appear to limit, change, or suppress the long-term dynamic compensation of the VOR, regardless of whether the animal had a previous UCP.