Spatial organization of the auditory nerve according to spontaneous discharge rate

Authors

  • Tetsuaki Kawase,

    1. Department of Otolaryngology, Tohoku University School of Medicine, Sendai 980, Japan
    2. Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts
    Search for more papers by this author
  • M. Charles Liberman

    Corresponding author
    1. Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts
    2. Departments of Otolaryngology and Physiology, Harvard Medical School, Boston, Massachusetts
    • Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA 02114
    Search for more papers by this author

Abstract

Auditory-nerve fibers in mammals have been classified into three functional subclasses according to spontaneous discharge rate (SR). In cat, the peripheral terminals of these SR groups are segregated around the sensory cell circumference (Liberman, '82, Science 216:1239–1241). The present study shows that this spatial segregation is at least partly maintained through the peripheral axonal course from sensory cell to spiral ganglion. Analysis of intracellularly labeled auditory-nerve fibers shows that peripheral axons and cell bodies of low-and medium-SR fibers tend to be found closer to scala vestibuli than high-SR fibers. Since low-and medium-SR fibers tend to be thinner, this SR-based segregation can also be demonstrated as a fiber-caliber gradient in the osseous spiral lamina. The issue of SR-based spatial segregation is relevant to reports that ganglion cells near scala vestibuli project to different regions of the cochlear nucleus than cells near scala tympani (Leake and Snyder, '89, J. Comp. Neurol. 281:612–629). Combining the results of the two studies suggests that there may be some SR-based spatial segregation of inputs to the cochlear nucleus. © 1992 Wiley-Liss, Inc.

Ancillary