Alterations of Round Window RecordedN1by Selective Sections of the Cochlear and Vestibular Nerves

Abstract

Electrical potentials recorded from the round window membrane of the cat cochlea are divided into neural (N₁ and N₂) and non-neural, hair-cell components (cochlear microphonics). N₁) and N₂) are grossly altered by the sectioning of the entire VIII cranial nerve. Selective sectioning of the cochlear and vestibular portions of the nerve at the internal meatus enabled a cause and effect relationship to be established. N₁–N₂ cleft distortion, N₁ amplitude increase and blockade of cochlear efferent (o.c.b.) stimulation was produced by sectioning of the vestibular fibers and cochlear efferents. Sectioning of the afferent fibers produced only a minor cleft distortion. Since initiation of the lesion does not depress N₁, and stimulation of either o.c.b. does, it is presumed that the changes produced are not related to discharge of the o.c. bundles but rather to removal of tonic efferent activity.