The synaptic organization of the horizontal vestibulo-ocular reflex in the frog

The neuronal organization of the horizontal vestibulo-ocular reflex (VOR) of frogs is reviewed and compared to results obtained from other vertebrates. Extensive similarities in the anatomical, physiological and pharmacological properties of the basic, three-neuronal reflex arc indicate the presence of a conservative, common plan for the VOR of vertebrates and its inhibitory control. To meet the requirements resulting from different locomotor patterns and from misalignments between semicircular canal and extraocular muscle planes, species-specific adaptations of the VOR performance must be present as well. Major differences in the performance of supplementary networks in different species provide a basis for this coadaptation.