Experiments are proposed which will utilize the physiological, developmental and genetic attributes of the zebrafish system to study vertebrate oculomoter function. The overall general hypothesis is that conserved genetic and anatomical profiles within segmented compartments of the hindbrain , called rhombomeres, are responsible for the phylogenetic conservation of oculomotor behaviors in vertebrates. Four specific aims are proposed to demonstrate the genetic basis of oculomotor function in the zebrafish with the expectation that these findings can be extrapolated to other vertebrates. The specific aims propose to describe the structure and function of visual and vestibular neurons along with circuits that control individual oculomotor behaviors as well as to establish the embryonic origin and genotype of each subgroup derived from the rhombomeres. Identification of oculomotor phenotypes within unique rhombomeric units will allow structural and behavioral analysis of relevant single gene mutations permitting assignment of single gene correlates to behavior.