The Parasympathetic Innervation of the Inner Ear and the Problem of Cochlear Efferents: Enzyme and Autoradiographic Studies
It has been assumed for many years that the matter of the existence of olivocochlear and vestibular efferents terminating on hair cells in the end organs of the inner ear is non-controversial. Opposing concepts that the centrally originating efferent fibers of the cochlear and vestibular nerves are parasympathetic (Ross 1969; Eyries and Chouard, 1970), and that the efferent-type terminals on hair cells might be collateral branches of spiral and vestibular ganglion nerve fibers (Ross, 1973) attracted little notice. However, two recent anatomical observations have served to refocus attention on these ideas. These are 1) the finding of multipolar neurons with synapses on their dendrites in human spiral ganglia (Kimura et al., 1979; Ota and Kimura, 1980), which supports the concept of a parasympathetic innervation of the inner ear; and 2) the observation that reciprocal synapses occur on outer hair cells in the human organ of Corti (Nadol, 1980), which substanties the notion that both afferent and efferent-type terminals can originate from the same parent nerve fiber. Additionally, a combined histochemical-physiological study (Goldberg and Fernandez, 1980) has shown that vestibular efferents originate bilaterally in the brain stem, lateral to the facial genu, in the monkey.
KeywordsHair Cell Outer Hair Cell Spiral Ganglion Vestibular Nerve Efferent Fiber
Unable to display preview. Download preview PDF.
- Arnold, F., 1851, “Handbuch der Anatomie des Menschen”, vol. 2, Herdersche Verlagshandlung, Freiburg im Breisgau.Google Scholar
- Chouard, C.-H., 1962, Recherches sur 1 organisation intra-axiale des formations motrices et parasympathiques du nerf facial, These Med., Paris.Google Scholar
- Crosby, E. C. and DeJonge, B. R., 1963, Experimental and clinical studies of the central connections and central relations of the facial nerve, Ann. Otol. Rhin. Laryng., 72: 735–755.Google Scholar
- Eyries, C. and Chouard, C.-H., 1970, Les anastomoses acoustico-faciales, Ann. Otolaryngol. (Paris), 87: 321–326.Google Scholar
- Kimura, R. S., Ota, C. Y. and Takahashi, T., 1979, Nerve fiber synapses on spiral ganglion cells in the human cochlea, Ann. Otol., 88: Supplement 62: 1–17.Google Scholar
- Nadol, J. B., Jr., 1980, Reciprocal synapses at the base of outer hair cells in the organ of Corti of man, Ann. Otol., (in press)Google Scholar
- Ross, M. D., 1973, Autonomic components of the VIIth nerve, Adv. Oto-Rhino-Laryng., 20: 316–336.Google Scholar