Journal of Neuroscience, Vol 8, 2836-2843, Copyright © 1988 by Society for Neuroscience
The induction and compensation of asymmetric eye movements following unilateral blockage of a horizontal semicircular canal in the rabbit
NH Barmack and VE Pettorossi
Department of Ophthalmology, Good Samaritan Hospital and Medical Center, Portland, Oregon 97209.
The influence of unilateral plugs of the left horizontal semicircular canal
(LHC plugs) of rabbits on the development and compensation of asymmetric
eye movements evoked by horizontal vestibular stimulation was studied. LHC
plugs caused an immediate reduction of 50-65% in the gain of the horizontal
vestibuloocular reflex (HVOR). This reduction in gain was achieved without
altering the symmetry of the HVOR, and was accompanied by a change in the
axial alignment of eye movements evoked by vestibular stimulation about the
vertical (HVOR) and longitudinal (VVOR) axes. Postoperative asymmetry of
eye movements developed 12-48 hr after the plugging operation. The
development of asymmetry was reduced if the rabbit was restrained for 24
hr, thereby minimizing vestibular stimulation following the plugging
operation. Over a 3-4 week period, the normal symmetry of eye movements was
restored and the axial alignments of the HVOR and VVOR returned to the
preoperative values. The gain of the HVOR did not recover. The horizontal
cervicoocular reflex (HCOR) was examined before the plugging operation and
after compensation of asymmetry was complete. The gain and phase of the
HCOR were not altered. A relatively simple set of explanations at a
cellular level is proposed to account for the induction and compensation of
asymmetric eye movements following a unilateral plug of the horizontal
semicircular canal.