Our overall goal is to understand the operation of the cochlea, in particular the mechanisms through which mechanical signals that enter the cochlea lead to the discharge of nerve fibers that leave the cochlea and enter the brain. We measure physiological variables at key stages in the cochleae of anesthetized alligator lizards and relate these through theoretical models of the underlying mechanisms. Much information has already been obtained on the alligator lizard car: the anatomy is well-described; measurements have been made of the mechanics of the middle and inner ear, the motion of the stereocilia, the receptor potentials of hair cells, the responses of supporting cells, the electromechanical environment of the receptor organ, and the spike discharges of cochlear nerve fibers. In this application, we propose a combined experimental and theoretical investigation of this ear with the aim of formulating a comprehensive model relating the sound pressure at the tympanic membrane to the discharges of cochlear nerve fibers in terms of the underlying structures and mechanisms. Many of these structures and mechanisms are common to all vertebrates. Hence, our findings should have general significance for understanding cochlear processes. Because our present understanding of cochlear processes is so incomplete, diagnosis and treatment of hearing impairments of cochlear origin are often purely empirical. More useful management of cochlear dysfunction will evolve when we have a clearer understanding of normal cochlear mechanisms.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
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Hearing Research Study Section (HAR)
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Massachusetts Institute of Technology
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Wadhwa, Neal; Chen, Justin G; Sellon, Jonathan B et al. (2017) Motion microscopy for visualizing and quantifying small motions. Proc Natl Acad Sci U S A 114:11639-11644
Sellon, Jonathan B; Ghaffari, Roozbeh; Freeman, Dennis M (2017) Geometric Requirements for Tectorial Membrane Traveling Waves in the Presence of Cochlear Loads. Biophys J 112:1059-1062
Farrahi, Shirin; Ghaffari, Roozbeh; Sellon, Jonathan B et al. (2016) Tectorial Membrane Traveling Waves Underlie Sharp Auditory Tuning in Humans. Biophys J 111:921-4
Sellon, Jonathan B; Farrahi, Shirin; Ghaffari, Roozbeh et al. (2015) Longitudinal spread of mechanical excitation through tectorial membrane traveling waves. Proc Natl Acad Sci U S A 112:12968-73
Sellon, Jonathan B; Ghaffari, Roozbeh; Farrahi, Shirin et al. (2014) Porosity controls spread of excitation in tectorial membrane traveling waves. Biophys J 106:1406-13
Ghaffari, Roozbeh; Page, Scott L; Farrahi, Shirin et al. (2013) Electrokinetic properties of the mammalian tectorial membrane. Proc Natl Acad Sci U S A 110:4279-84
Masaki, Kinuko; Ghaffari, Roozbeh; Gu, Jianwen Wendy et al. (2010) Tectorial membrane material properties in Tecta(Y)(1870C/+) heterozygous mice. Biophys J 99:3274-81
Ghaffari, Roozbeh; Aranyosi, Alexander J; Richardson, Guy P et al. (2010) Tectorial membrane travelling waves underlie abnormal hearing in Tectb mutant mice. Nat Commun 1:96
Masaki, Kinuko; Gu, Jianwen Wendy; Ghaffari, Roozbeh et al. (2009) Col11a2 deletion reveals the molecular basis for tectorial membrane mechanical anisotropy. Biophys J 96:4717-24
Gu, Jianwen Wendy; Hemmert, Werner; Freeman, Dennis M et al. (2008) Frequency-dependent shear impedance of the tectorial membrane. Biophys J 95:2529-38

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