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J Neurosci. 2012 Aug 1;32(31):10522-9. doi: 10.1523/JNEUROSCI.1138-12.2012.

Traveling waves on the organ of corti of the chinchilla cochlea: spatial trajectories of inner hair cell depolarization inferred from responses of auditory-nerve fibers.

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  • 1Hugh Knowles Center, Department of Communication Sciences and Disorders, Northwestern University, Evanston, Illinois 60208-3550, USA.

Abstract

Spatial magnitude and phase profiles for inner hair cell (IHC) depolarization throughout the chinchilla cochlea were inferred from responses of auditory-nerve fibers (ANFs) to threshold- and moderate-level tones and tone complexes. Firing-rate profiles for frequencies ≤2 kHz are bimodal, with the major peak at the characteristic place and a secondary peak at 3-5 mm from the extreme base. Response-phase trajectories are synchronous with peak outward stapes displacement at the extreme cochlear base and accumulate 1.5 period lags at the characteristic places. High-frequency phase trajectories are very similar to the trajectories of basilar-membrane peak velocity toward scala tympani. Low-frequency phase trajectories undergo a polarity flip in a region, 6.5-9 mm from the cochlear base, where traveling-wave phase velocity attains a local minimum and a local maximum and where the onset latencies of near-threshold impulse responses computed from responses to near-threshold white noise exhibit a local minimum. That region is the same where frequency-threshold tuning curves of ANFs undergo a shape transition. Since depolarization of IHCs presumably indicates the mechanical stimulus to their stereocilia, the present results suggest that distinct low-frequency forward waves of organ of Corti vibration are launched simultaneously at the extreme base of the cochlea and at the 6.5-9 mm transition region, from where antiphasic reflections arise.

PMID:
22855802
[PubMed - indexed for MEDLINE]
PMCID:
PMC3436599
Free PMC Article
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