Background

The vestibular system detects changes in head and body position, controls gaze, and facilitates higher-level cognitive perception functions. It comprises three semicircular canals and two otolith organs (the utricle and saccule), which mediate sensitivity to rotational and linear (including gravitational) head movements, respectively. Vestibulo-ocular reflexes (VORs) are commonly used in clinical testing [1] and have also been part of standard vestibular function tests in primate studies [2–4]. VORs can be classified into angular VOR (aVOR), induced by rotational accelerations and primarily driven by signals from horizontal semicircular canal cristae (HSCC) [5,6], and translational VORs (tVORs), such as linear VOR (LVOR) and off-vertical axis rotation (OVAR), which provide otolith stimulus [7,8]. OVAR typically entails constant rotational velocity of the mouse head about an axis that is tilted to the Earth's vertical axis. After achieving steady state rotation, the semicircular canal response decays, and the resulting ocular response originates from otoliths [2,7]. LVOR response is too small to provide reliable estimates of otolith function [9], but OVAR signals are sufficiently robust, and OVAR stimulus could be easily combined with aVOR stimulus into one machine. Therefore, the combination of aVOR and OVAR can form the basis of a complete functional test for the peripheral vestibular organ. The purpose of this protocol is to provide a detailed procedure to encourage further study of the vestibular system's function.