Primate Translational Vestibulo-Ocular Reflexes. III. Effects Of Bilateral Labyrinthine Electrical Stimulation. Dora E. Angelaki, M. Quinn McHenry, J. David Dickman and Adrian A. Perachio. Dept. of Surgery (Otolaryngology) and Anatomy, University of Mississippi Medical Center, Jackson MS and Dept. of Otolaryngology and Anatomy, University of Texas Medical Branch, Galveston TX.
APStracts 6:0528N, 1999.
The effects of functional, reversible ablation and potential recruitment of the most irregular otolith afferents on the dynamics and sensitivity of the translational vestibulo-ocular reflexes (trVORs) were investigated in rhesus monkeys trained to fixate near and far targets. Translational motion stimuli consisted of either steady-state lateral and fore-aft sinusoidal oscillations or short-lasting transient lateral head displacements. Short-duration (usually <2s) anodal (inhibitory) and cathodal (excitatory) currents (50-100 ?A) were delivered bilaterally during motion. In the presence of anodal labyrinthine stimulation, trVOR sensitivity and its dependence on viewing distance were significantly decreased. In addition, anodal currents significantly increased phase lags. During transient motion, anodal stimulation resulted in significantly lower initial eye acceleration and more sluggish responses. Cathodal currents tended to have opposite effects. The main characteristics of these results were simulated by a simple model where both regularly and irregularly discharging afferents contribute to the trVORs. Anodal labyrinthine currents were also found to decrease eye velocity during long-duration, constant velocity rotations, although results were generally more variable compared to those during translational motion.
Received 5 February 1999; accepted in final form 18 October 1999.
APS Manuscript Number J089-9.
Article publication pending Journal of Neurophysiology.
ISSN 1080-4757 Copyright 1999 The American Physiological Society.
Published in APStracts on 21 December 1999