Document Detail

Long-term effects of sectioning the olivocochlear bundle in neonatal cats.
MedLine Citation:
PMID:  9570815     Owner:  NLM     Status:  MEDLINE    
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.
E J Walsh; J McGee; S L McFadden; M C Liberman
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of neuroscience : the official journal of the Society for Neuroscience     Volume:  18     ISSN:  0270-6474     ISO Abbreviation:  J. Neurosci.     Publication Date:  1998 May 
Date Detail:
Created Date:  1998-06-01     Completed Date:  1998-06-01     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  8102140     Medline TA:  J Neurosci     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  3859-69     Citation Subset:  IM    
Boys Town National Research Hospital, Omaha, Nebraska 68131, USA.
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MeSH Terms
Age Factors
Animals, Newborn
Auditory Threshold / physiology
Cochlear Nucleus / growth & development,  physiology*,  surgery
Nerve Fibers / physiology
Olivary Nucleus / growth & development,  physiology*,  surgery
Pitch Discrimination / physiology
Vestibulocochlear Nerve / growth & development,  physiology*,  surgery
Grant Support

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