Vestibular compensation: a review of the oculomotor, neural, and clinical consequences of unilateral vestibular loss.

Vestibular sensory input is just one sensory input involved in the control of functions such as gaze and posture. The recovery of gaze and posture control after partial or complete unilateral loss of vestibular input is reviewed. The relatively rapid and apparently complete behavioral recovery after unilateral vestibular loss was once regarded as justifying vestibular compensation being used as a text-book example of plasticity in the CNS. This review emphasizes how false that impression is: Detailed examination shows that vestibular compensation is not a single process that recovers completely at a rapid rate but is made up of a number of subprocesses that recover to different levels and at different rates. In some subprocesses there is very modest recovery; in other subprocesses there is probably substitution of other sensory input for the affected vestibular input. It also seems that in some instances new behavioral strategies appear to be learned to allow gaze and posture control to operate as if normal. Recent evidence concerning the physiological and pharmacological mechanisms underlying vestibular compensation is reviewed.