PHYSIOLOGICAL AND ANATOMICAL CHARACTERISTICS OF THE VESTIBULAR GANGLION OF THE BULL FROG

Spatial distributions of the vestibular nerve fibers from end organs to the vestibular ganglion (VG) were studied using physiological and anatomical methods. Physiologically, ampullary nerve compound action potentials (AP) were recorded from VG. Anatomically, HRP (horseradish peroxidase) was injected into the cut end of the ampullary nerve, and the stained neural elements were counted on serial sections. Nerve fibers from the anterior semicircular canal (SC) were distributed in the anterior half of the VG. The horizontal SC nerves were also distributed in the anterior half of the VG, but tended to be posterior. The posterior SC nerves were found predominantly in the posterior half and the antero-dorsal portions of the VG. These distribution patterns corresponded well to those confirmed by recording of AP. Furthermore, neural connections were found between the superior and the inferior vestibular nerves, suggesting receptor-receptor fibers. The majority of these fibers were small in diameter.