title: 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.
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.
authors.affiliation: Hugh Knowles Center, Department of Communication Sciences and Disorders, Northwestern University, Evanston, Illinois 60208-3550, USA.
authors.forename: Andrei N
authors.initials: AN
authors.lastname: Temchin
authors.forename: Alberto
authors.initials: A
authors.lastname: Recio-Spinoso
authors.forename: Hongxue
authors.initials: H
authors.lastname: Cai
authors.forename: Mario A
authors.initials: MA
authors.lastname: Ruggero
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001309:Auditory Threshold / Q000502:physiology; D001489:Basilar Membrane / Q000294:innervation / Q000502:physiology; D002682:Chinchilla / Q000033:anatomy & histology; D003051:Cochlea / Q000033:anatomy & histology / Q000502:physiology*; D003056:Cochlear Nerve / Q000502:physiology*; D004558:Electric Stimulation; D006199:Hair Cells, Auditory, Inner / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D009925:Organ of Corti / Q000166:cytology*; D011601:Psychophysics; D011930:Reaction Time / Q000502:physiology; D013680:Tectorial Membrane / Q000294:innervation / Q000502:physiology; D013997:Time Factors; D014732:Vibration