Test for Otolith Organs with Barbecue Rotation

Abstract

In the sitting position, vertical axis head rotation stimulates only the horizontal canal. In the supine position, horizontal axis rotation, so-called barbecue rotation, is a stimulus to both the horizontal canal and otolith organs. We compared dynamic otolith response to these two types of harmonic rotations in 15 normal subjects. The subjects' heads were rotated, passively with eyes open but covered, at the following frequencies: 0.17, 0.33, 0.50, 0.67 and 1.00 Hz. Head movement and eye movement were recorded by scleral search coil technique. Compensatory eye movements were present on each record. Vesti-bulo-ocular reflex (VOR) gain was calculated using peak-to-peak velocity of the eye and head. At all frequencies the VOR gain of horizontal axis rotation was larger than that of vertical axis rotation. This difference was maximal at the lowest frequency, 0.17 Hz, suggesting that dynamic otolith stimulus improves VOR at low frequencies.

Key Words:

• vertical axis yaw rotation
• horizontal axis yaw rotation
• vestibulo-ocular reflex
• otolith-ocular reflex