Plasticity of the vestibulo-ocular reflex.

The plasticity of the vestibulo-ocular reflex (VOR) was investigated by examining three different processes, namely vestibular habituation to repeated head angular velocity steps, vestibular compensation after hemilabyrinthectomy, and vestibular compensation in patients suffering from unilateral Ménière's disease. The first two processes were examined in the cat, while the third process was studied in man. A quantification of these processes was obtained by computing some parameters characterizing the diagrams of the slow cumulative eye position (SCEP) and the slow phase eye velocity (SPEV) or by using the nystagmic responses to identify the main parameters of VOR. Finally, an attempt was made to interpretate the plasticity of VOR in terms of a multilevel hierarchical organization of the system controlling vestibularly induced eye movements.