Vestibular Neurophysiology

Abstract

An important function of the vestibular system is to secure visual stabilization during head movement, and at low-frequency movements the optokinetic and pursuit systems collaborate to this end. Oscillopsia results when eye velocity fails to match head velocity. Simple bedside tests to identify oscillopsia and impaired cancellation of the vestibulo-ocular reflex (VOR) are described. Adaptive plasticity, directed to the goal of maintenance of foveation despite marked changes in the external (e.g., reversed visual surround) or internal (e.g., after labyrinthectomy) environment, is an important attribute of the vestibular system. The flocculus and some of its connections are essential to this function. Reduction of floccular efficiency, as in the elderly, might be an important cause of defective adaptation to a vestibular lesion, such as labyrinthectomy.