Classical conditioning using vestibular reflexes.

Adaptation of the vestibulo-ocular reflex (VOR) is one of the principal models for studying motor learning in the mammalian CNS. However, there has been no previous comprehensive attempt to understand the behavioral characteristics of VOR adaptation in terms of traditional psychological learning theory. To accomplish this objective, the effectiveness of vestibular-evoked responses in serving as the conditioned or unconditioned stimulus in classical conditioning paradigms is first reviewed. Then, the various procedures for eliciting VOR adaptation are reviewed from the perspective of their similarity to standard classical conditioning protocols. A systematic analysis of Western and Russian literature yielded a relatively small number of studies that explicitly used vestibular reflexes in classical conditioning paradigms, and they report a wide range in success. Potential explanations for these diverse findings are discussed. A comprehensive categorization of the behavioral parallels between VOR adaptation and classical conditioning is then presented. Viewing VOR adaptation as a form of classical conditioning is a useful heuristic device and leads directly to the description of further behavioral experiments that could throw additional light on general mechanisms for inducing neural plasticity. Such an exercise is of benefit in order to further understand the common framework which might exist between VOR adaptation and other models of motor learning (for example, rabbit eye blink conditioning).