title: Vibration of the organ of Corti within the cochlear apex in mice.
abstract: The tonotopic map of the mammalian cochlea is commonly thought to be determined by the passive mechanical properties of the basilar membrane. The other tissues and cells that make up the organ of Corti also have passive mechanical properties; however, their roles are less well understood. In addition, active forces produced by outer hair cells (OHCs) enhance the vibration of the basilar membrane, termed cochlear amplification. Here, we studied how these biomechanical components interact using optical coherence tomography, which permits vibratory measurements within tissue. We measured not only classical basilar membrane tuning curves, but also vibratory responses from the rest of the organ of Corti within the mouse cochlear apex in vivo. As expected, basilar membrane tuning was sharp in live mice and broad in dead mice. Interestingly, the vibratory response of the region lateral to the OHCs, the "lateral compartment," demonstrated frequency-dependent phase differences relative to the basilar membrane. This was sharply tuned in both live and dead mice. We then measured basilar membrane and lateral compartment vibration in transgenic mice with targeted alterations in cochlear mechanics. Prestin(499/499), Prestin(-/-), and Tecta(C1509G/C1509G) mice demonstrated no cochlear amplification but maintained the lateral compartment phase difference. In contrast, Sfswap(Tg/Tg) mice maintained cochlear amplification but did not demonstrate the lateral compartment phase difference. These data indicate that the organ of Corti has complex micromechanical vibratory characteristics, with passive, yet sharply tuned, vibratory characteristics associated with the supporting cells. These characteristics may tune OHC force generation to produce the sharp frequency selectivity of mammalian hearing.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California; Department of Bioengineering, Rice University, Houston, Texas;
authors.forename: Simon S
authors.initials: SS
authors.lastname: Gao
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California;
authors.forename: Rosalie
authors.initials: R
authors.lastname: Wang
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California;
authors.forename: Patrick D
authors.initials: PD
authors.lastname: Raphael
authors.affiliation: Department of Neuroscience, Baylor College of Medicine, Houston, Texas;
authors.forename: Yalda
authors.initials: Y
authors.lastname: Moayedi
authors.affiliation: Department of Neuroscience, Baylor College of Medicine, Houston, Texas; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas; Program in Developmental Biology, Baylor College of Medicine, Houston, Texas;
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Groves
authors.affiliation: Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee; and.
authors.forename: Jian
authors.initials: J
authors.lastname: Zuo
authors.affiliation: Department of Biomedical Engineering, Texas A&M University, College Station, Texas.
authors.forename: Brian E
authors.initials: BE
authors.lastname: Applegate
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, California; joghalai@stanford.edu.
authors.forename: John S
authors.initials: JS
authors.lastname: Oghalai
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001489:Basilar Membrane / Q000502:physiology*; D001696:Biomechanical Phenomena; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000502:physiology; D005260:Female; D058851:GPI-Linked Proteins / Q000235:genetics / Q000502:physiology; D018072:Hair Cells, Auditory, Outer / Q000502:physiology; D006309:Hearing / Q000502:physiology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D020409:Molecular Motor Proteins / Q000235:genetics / Q000502:physiology; D009925:Organ of Corti / Q000502:physiology*; D014732:Vibration
chemical_list: D016326:Extracellular Matrix Proteins; D058851:GPI-Linked Proteins; D020409:Molecular Motor Proteins; C498720:Pres protein, mouse; C105350:Tecta protein, mouse
keywords: biomechanics; cochlea; cochlear amplifier; electromotility; hair cell; hearing; hearing loss