The vestibular system of the inner ear acts as a six degree-of-freedom (DOF) motion sensor of head rotational velocity and gravitoinertial acceleration (GIA), the latter being the sum of acceleration due to gravity and linear/translational head movement. There are two classes of sensors in the ear: three mutually orthogonal rotation sensors (semicircular canals, SCCs) and two GIA sensors (utricle and saccule, collectively called otolith end organs). Each of the inner ear's five inertial sensors encodes motion using pulse frequency modulation (PFM) of afferent neuron firing rates above and below naturally nonzero spontaneous activity rates [1].

Sensation of head motion drives ocular, postural, and autonomic reflexes that help to maintain steady vision, stable gait, and balance. Individuals with profound bilateral vestibular deficiency (BVD) suffer reduced quality of life due to poor visual acuity during head movement, illusory motion of visible objects during head movements, postural instability, and chronic disequilibrium....

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