Morphometry of intracellularly labeled neurons of the auditory nerve: Correlations with functional properties

TLDR

Functional properties of auditory‑nerve fibers allow prediction of virtually all other aspects of their response. The study injected horseradish peroxidase into single auditory‑nerve fibers after measuring their tuning, characteristic frequency, and spontaneous discharge, then reconstructed the fibers from cochlear hair cells to the cochlear nucleus and quantified axonal diameter, length, internodal distances, and cell‑body morphology. Morphological parameters correlated with characteristic frequency, but only axonal diameter correlated with spontaneous discharge rate.

Abstract

Abstract Single auditory‐nerve fibers were injected with horseradish peroxidase after their tuning properties, characteristic frequencies, and spontaneous discharge rates were measured. From these functional properties virtually all other aspects of auditory‐nerve response can be predicted. Labeled fibers were reconstructed from the point of peripheral termination on cochlear hair cells to the point at which they enter the cochlear nucleus. Several morphological properties were measured at the light‐microscopic level, including axonal diameter, axonal length, internodal distances, cell‐body area, and cell‐body shape. All of these parameters were correlated, though some weakly, with characteristic frequency. However, only axonal diameter was correlated with spontaneous discharge rate.