Affiliations: [a] Department of Otolaryngology, St. Marianna University School of Medicine, Kanagawa, Japan | [b] Departments of Otolaryngology and Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania | [c] Departments of Otolaryngology, Neurology, and Electrical Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania
Note: [*] Reprint address: Joseph M. Furman, M.D., Ph.D., University of Pittsburgh School of Medicine, The Eye & Ear Institute Building, 200 Lothrop Street, Pittsburgh, PA 15213 USA. Fax: (412) 647-2080; Ph: (412) 647-2117.
Abstract: The duration of post-rotatory nystagmus is known to be shortened by head tilt, a phenomenon that has been attributed to rapid discharge of the velocity storage mechanism. The relative importance of the various sensory signals associated with post-rotatory head tilt is unknown. Using both earth-vertical axis and off-vertical axis rotation, we investigated this issue in humans by combining sudden termination of constant velocity rotation with several post-rotatory maneuvers that stimulated combinations of otolith organ, somatosensory, and vertical semicircular canal afferents. Results indicated that horizontal post-rotatory nystagmus was shortened by maneuvers that move the head from upright to off-vertical and by cessation of dynamic otolith stimuli. Somatosensory, neck afferent, and transient vestibular stimulation had no consistent effect. We conclude that tilt suppression of postrotatory nystagmus and the short time constant following off-vertical axis rotation is primarily a function of otolith influence on the velocity storage system.
