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Changes in the Vestibulo‐Ocular Reflex after Plugging of the Semicircular Canals
Author(s) -
YAKUSHIN SERGEI B.,
DAI MINGJIA,
RAPHAN THEODORE,
SUZUKI JUNICHI,
ARAI YASUKO,
COHEN BERNARD
Publication year - 2001
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.2001.tb03753.x
Subject(s) - semicircular canal , vestibular system , vestibulo–ocular reflex , geology , reflex , nystagmus , kinematics , head tilt , geodesy , physics , audiology , biology , classical mechanics , medicine , neuroscience , optometry
A bstract : The gain of the angular vestibulo‐ocular reflex (aVOR) was determined in monkeys by rotation about a spatial vertical axis while upright or statically tilted forward and backward. Horizontal, vertical, and roll gains were determined at each head orientation and plotted as a function of head tilt. Before canal plugging, animals had maximal (spatial) horizontal gains when upright (spatial phase 0°) and maximal roll gains when tilted forward or backward 90°. Plugging caused striking changes in the characteristics of the aVOR gains at low frequencies. After plugging of the vertical canals, maximal horizontal and roll gains both occurred at head tilts of ∼30° forward. When the lateral canals were plugged, maximal horizontal and roll responses occurred when the head was tilted back ∼50°. The aVOR gains of the canal‐plugged animals were also affected by stimulus frequency. In every instance, as stimulus frequency increased, the spatial phases shifted toward the normal response, that is, the response before plugging. This normalization effect was observed even in the animals with all six semicircular canals plugged, indicating that normalization was not due to spatial adaptation. A three‐dimensional dynamic and kinematic model of the aVOR was able to account for all types of canal plugging by a simple change in the dominant time constant of the plugged canals from 3 s to 5 s to ∼0.07 s. The model accurately predicted responses of the normal and canal‐plugged animals at all frequencies. These data show that the central vestibular system does not spatially adapt to losses resulting from canal plugging.