Role of the cerebellum during motor learning in the vestibulo-ocular reflex: Different mechanisms in different species?

The vestibulo-ocular reflex operates continuously to prevent visual images from slipping across the retina during head turns. The normal excellent performance of this reflex is established and maintained in part by a long-term adaptive process whose function depends on an important contribution from the flocculus of the cerebellum. In this review, I consider two models that have been proposed to explain the role of the flocculus; particular attention is paid to the evidence provided by experiments that have monitored the activity of single cells in the flocculus of alert animals. Because the two models are based on experimental evidence derived from two species that have qualitatively different eye movements —the albino rabbit and the rhesus monkey —I also consider the possibility that the role of the cerebellum differs in the two species.