Innervation Patterns in the Organ of Corti of the Cat

The afferent and efferent nerve supply of the organ of Corti was studied after transsection of the olivo cochlear fibres in the vestibular nerve, the vestibular root, or at the floor of the fourth ventricle. After elimination of the efferent fibres by degeneration, the distribution patterns of the afferent fibres were evaluated with electron and light-microscopy. In the cat, all tunnel crossing radial fibres appeared to belong to the efferent innervation. The afferent fibres to the outer hair cells crossed the tunnel at the bottom as basilar fibres. The majority of afferent neurons ended at the inner hair cells and only a minority were associated with the outer hair cells. After selective transsection of the crossed olivo cochlear fibres, a great number of the efferent endings at the outer hair cells degenerated but also the number of internal spiral fibres seemed to be reduced.