Auditory nerve fiber responses following chronic cochlear de-efferentation.
The aim of the present study was to examine the role of the olivocochlear system in auditory processing by examining the long-term effects of cochlear de-efferentation on auditory nerve response properties in adult chinchillas. Spontaneous rates, response thresholds, tuning curves, discharge rate-level functions, and adaptation of single auditory nerve fibers were measured in chinchillas with complete cochlear de-efferentation produced by sectioning the olivocochlear bundle in the internal auditory meatus. De-efferentation was verified as successful on the basis of acetylcholinesterase staining of surface preparations of the organ of Corti. Following chronic de-efferentation, there was a striking decrease in spontaneous rate, consistent with earlier observations in cats. In addition, the present study shows that complete de-efferentation results in: (1) increased driven discharge rates and decreased dynamic range of discharge rate-level functions, (2) larger onset-to-steady state ratio of discharge rate at moderate intensities, and (3) a hypersensitive tail of the tuning curve. These effects, largely confined to neurons that were most sensitive to frequencies between 2-8 kHz, indicate that the cochlear efferent system is important in maintaining normal function (e.g., frequency and intensity selectivity) of the auditory periphery by modulating auditory nerve fiber response properties.
Zheng
X Y
XY
Center for Hearing and Deafness, State University of New York at Buffalo, 14214, USA. xyz@acsu.buffalo.edu
Henderson
D
D
McFadden
S L
SL
Ding
D L
DL
Salvi
R J
RJ
D000110:Acetylcholinesterase / Q000378:metabolism; D000161:Acoustic Stimulation; D000818:Animals; D002682:Chinchilla; D003051:Cochlea / Q000201:enzymology / Q000294:innervation*; D003714:Denervation; D004056:Differential Threshold / Q000502:physiology; D004525:Efferent Pathways / Q000502:physiology; D004594:Electrophysiology; D005260:Female; D006651:Histocytochemistry; D008297:Male; D009412:Nerve Fibers / Q000502:physiology; D000159:Vestibulocochlear Nerve / Q000502:physiology*
D000110:Acetylcholinesterase