CENTRAL PROJECTION OF THE VIIITH-CRANIAL NERVE IN THE FROG

With the aid of the cobalt labeling technique the following termination areas of the vestibulocochlear nerve are found in the frog. The nucleus cochlearis receives fibers from the cochlear primordia, i.e. the amphibian and basilar papillae and the lagena. The terminals form a spherical pericellular feltwork characteristic of auditory fibers. The nucleus saccularis is supplied exclusively by fibers of sacculus origin terminating with a similar kind of auditory characteristic pattern. The nuclei vestibularis lateralis (Deiters), superior, descendens and medialis can be discerned in the vestibular area. They are supplied by fibers from all vestibular receptors including the lagena. The corpus and lobus auricularis of the cerebellum receive an extensive vestibular projection ending in mossy terminals. Vestibular fibers can be traced also to the oliva superior (from the lagena and sacculus only), the reticular formation, the spinal nucleus of the trigeminus, the motor nuclei of nerves V, accessory VI, IX and XII, and to the dorsal column nuclei. It is concluded that the frog possesses the whole complement of the vestibular nuclear complex known in mammals, although some parts are in primordial form. The nucleus saccularis with the auditory type of terminals may represent a prospective nucleus cochlearis ventralis thus complementing the auditory nuclear complex as well. The extensive primary vestibular projections to other brain stem structures may play a role in the various righting and postural reactions. © 1979.