FAA Office of Aerospace Medicine
Civil Aerospace Medical Institute

Report No: DOT/FAA/AM-67/02

Title and Subtitle: Adaptation to vestibular disorientation. IV. Responses to angular acceleration and to bilateral caloric stimulation following unilateral caloric habituation.

Report Date: January 1967

Authors: Mertens RA, Collins WE.

Abstract: The paper provides information that angular acceleration tests of the vestibular system transcend clinical caloric tests in revealing adaptation to angular accelerations as experienced in rotary motions, including flight situations. The caloric test is definitely not a substitute for angular acceleration tests. The vestibular system is the system primarily involved in disorientation and vertigo.

Adaptation of vestibular responses was obtained by clinical methods (unilateral calorization) and the generalization of this state of adaptation to bilateral (caloric and rotatory) stimulation was examined. Data indicate positive transfer effects for the clinical stimuli but no clear transfer of adaptation occurred with respect to responses elicited by angular accelerations.

Further, adaptation of nystagmus by repeated angular accelerations failed to transfer to clinical stimulation. Differences in modes of activation between methods and influences related to stimulation of the gravity receptor were cited as possible causes for the lack of transfer. A subject's state of adaptation to angular accelerations may not be adequately assessed by clinical caloric tests.

Key Words: acceleration, adaptation (physiology), vestibular apparatus, habituation learning, nystagmus, vertigo, stimulation (physiology), response (biology), rotation, aviation medicine.

No. of Pages: 16