The olivocochlear bundle (OCB) was cut in neonatal cats to evaluate its role in the development of normal cochlear function. Approximately 1 year after deefferentation, acute auditory nerve fiber (ANF) recordings were made from lesioned animals, lesion shams, and normal controls. The degree of deefferentation was quantified via light microscopic evaluation of the density of OCB fascicles in the tunnel of Corti, and selected cases were analyzed via electron microscopy. In the most successful cases, the deefferentation was virtually complete. ANFs from successfully lesioned animals exhibited significant pathophysiology compared with normals and with other animals in which the surgery failed to interrupt the OCB. Thresholds at the characteristic frequency (CF), the frequency at which ANFs are most sensitive, were elevated across the CF range, with maximal effects for CFs in the 10 kHz region. Frequency threshold or tuning curves displayed reduction of tip-to-tail ratios (the difference between CF and low-frequency “tail” thresholds) and decreased sharpness of tuning. These pathological changes are generally associated with outer hair cell (OHC) damage. However, light microscopic histological analysis showed minimal hair cell loss and no significant differences between normal and deefferented groups. Spontaneous discharge rates (SRs) were lower than normal; however, those fibers with the highest SRs remained more sensitive than those with lower SRs. Findings suggest that the interaction between OC efferents and OHCs early in development may be critical for full expression of active mechanical processes.
Long-Term Effects of Sectioning the Olivocochlear Bundle in Neonatal Cats
E. Walsh,J. McGee,S. McFadden,M. C. Liberman
Published 1998 in Journal of Neuroscience
ABSTRACT
PUBLICATION RECORD
- Publication year
1998
- Venue
Journal of Neuroscience
- Publication date
1998-05-15
- Fields of study
Biology, Medicine
- Identifiers
- External record
- Source metadata
Semantic Scholar, PubMed
CITATION MAP
EXTRACTION MAP
CLAIMS
CONCEPTS
- active mechanical processes
Cochlear mechanical amplification processes that sharpen sensitivity and tuning.
Aliases: active mechanics
- auditory nerve fiber
An individual cochlear afferent fiber whose responses were recorded acutely.
Aliases: ANF
- characteristic frequency
The frequency at which an auditory nerve fiber is most sensitive.
Aliases: CF
- deefferentation
Loss or interruption of efferent innervation to the cochlea.
Aliases: de-efferentation, deafferentation
- olivocochlear bundle
A descending efferent fiber bundle connecting the brainstem to the cochlea.
Aliases: OCB
- outer hair cell
A cochlear sensory cell involved in amplification and frequency selectivity.
Aliases: OHC
- sharpness of tuning
A measure of how narrowly an auditory nerve fiber responds around its preferred frequency.
Aliases: tuning sharpness
- spontaneous discharge rate
The baseline firing rate of an auditory nerve fiber in the absence of sound.
Aliases: SR
- tip-to-tail ratio
The difference between a tuning curve's characteristic-frequency threshold and its low-frequency tail threshold.
Aliases: tip-tail ratio
REFERENCES
Showing 1-95 of 95 references · Page 1 of 1