Affiliations: [a] Department of Otolaryngology, St. Michael's Hospital, Toronto, Ontario, Canada | [b] Department of Pharmacology, University of Toronto, Ontario, Canada | [c] Defense and Civil Institute of Environmental Medicine, North York, Ontario, Canada
Note: [*] Reprint address: Walter H. Johnson, Ph.D., Director of Research, Department of Otolaryngology, St. Michael's Hospital, 8C, 30 Bond St., Toronto, Ontario M5B 1W8 Canada. Tel.: +1 416 864 5257; Fax: +1 416 864 5694; E-mail: greenp@smh.toronto.on.ca
Abstract: The objective of this study was to determine the importance, if any, of the non-auditory labyrinth of the inner ear in visually induced nausea and self-vection in subjects exposed to a moving visual field with and without concomitant pitching head movements. Subjects teated were 15 normals, 18 unilateral labyrinthectomies and 6 bilateral labyrinthectomies. The findings show a higher incidence of pseudo-Coriolis induced nausea in normal subjects compared to unilateral and bilateral labyrinthectomized subjects. When the subjects were exposed to the moving visual field only (no head movement), pronounced self-vection occurred in all subjects, but with earlier onset in the bilateral labyrinthine defective subjects as compared to normal and unilateral defective subjects. The subjective intensities of self-vections reported by labyrinth-defectives were much more pronounced as compared to normal subjects, and it is apparent that visual input in these subjects achieves much more importance in maintaining compensatory eye movements, and the gain of neck reflexes is enhanced. The findings that visual stimulation is more effective in producing the disabling effects after labyrinthine destruction could possibly be explained by enhancement of vision after loss of labyrinthine sensory input, and the gain in neck reflexes is also enhanced after labyrinthectomy.
