Effect of Chronic Section of the Eighth Nerve in the Cat

The N₁ and N₂ recorded at the round window have been found to be present for 24 hours after complete section of the eighth nerve. Cats with eighth‐nerve section were used in a series of experiments to determine if the N₁ and N₂ persisted for longer periods of time than previously reported. The opposite ear was destroyed at the time of the terminal experiment. In all the animals tested, cochlear potentials were found to be normal. The findings revealed that the N₁ and N₂ persisted in the completely sectioned eighth nerve up to 72 hours after operation. At this time, the N₂ began to disappear. At 4 to 5 days postoperatively, both the N₁ and N₂ completely disappeared leaving a new phenomena in its place. This phenomena is called the W phenomena. It occurs at approximately the same time that the N₂ did. It is a biphasic positive potential. This potential does not change polarity if the click‐stimulus polarity is changed; it is more sensitive to anoxia than the cochlear potential, and behaves in many ways like a nerve potential. It is felt that this potential was not the dc potential that has been observed by others, because it occurs so late after the cochlear response. Histological examination of the ears of the animals revealed complete section of the eighth nerve with no preservation of the cochlear nucleus. There was marked degeneration of the spiral ganglion cells in the modiolus; however, consistent with previous findings, Scarpa's ganglion remained intact. It is felt that the W response may either come from the few remaining ganglion cells in the modiolus or that it may originate from the neural epithelium which is innervated by the fibers from Scarpa's ganglion.