FAA Office of Aerospace Medicine
Civil Aerospace Medical Institute

Report No: DOT/FAA/AM-68/02

Title and Subtitle: Adaptation to vestibular disorientation: IX. Influence of head position on the habituation of vertical nystagmus

Report Date: March 1968

Authors: Collins WE.

Abstract: Interactions of linear and angular accelerations are frequently experienced by pilots during aircraft maneuvers. Several recent studies have indicated that the otoliths (detectors of linear acceleration) may influence responses of the semicircular canals (detectors of angular acceleration). To obtain some clearer evidence of such possible effects, a laboratory situation was designed to provide a minimally complex test of otolith-semicircular canal interactions.

Because cats show very rapid habituation (reduction) of the eye-movement response (nystagmus) to rotatory stimulation, eight such animals were repeatedly stimulated by angular accelerations. For all habituation trials, the saggital plane of the head and body of each animal was in the plane of rotation. A clear reduction of vertical nystagmus was obtained. By changing the position of the animals 180 deg. after the adaptation trials, the same set of semicircular canals was stimulated but the orientation of the otoliths was changed. Habituation was specific to the practiced direction of nystagmus and to the practiced head (otolith) position.

Key Words: Aviation Medicine, Semicircular Canals, Vestibular Apparatus, Nystagamus, Pilots, Accerleration, Scientific Research, Laboratory Animals, Cats, Adaptation (physiology), Head (anatomy)

No. of Pages: 8