Central projections of the octaval system in the thornback ray Platyrhinoidis triseriata

Octaval nerve centers are studied at medullary and mesencephalic levels after electrical stimulation of the VIIIth nerve and selected brain areas. Recording of evoked potentials shows that primary afferent input is relayed to the anterior, magnocellular, and descending octaval nuclei in the medulla as well as to the cerebellar auricle. The three medullary nuclei project to their contralateral homologues via second-order commissural fibers. Both the ipsi- and contralateral anterior and magnocellular nuclei pass on information via secondary neurons to the oculomotor area and the torus semicircularis in the midbrain.