Figure 1. Structures and functions of the vestibular system.

(A) Three orthogonal semicircular canals (anterior, posterior, and horizontal) provide angular head motion signals, and two otolith organs (utricle and saccule) provide linear acceleration signals. These signals travel via afferent fibers to the vestibular nuclei, where they contribute to pathways involved in visual stability, postural stability, and perception and navigation. Inset: Within the ampulla of each semicircular canal, the hair cells are arranged such that their axis of maximum sensitivity is aligned with the fluid motion direction. (B) At rest, afferents fire at a baseline rate (left). During head motion, this baseline is then modulated up (middle) or down (right) to encode head motion in two opposing directions.