Alterations of Round Window Recorded N₁ by 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.