The overall goal of the proposed research is to understand how inner ear mechanisms determine the neural code that relates sounds to nerve messages that enter the brain. Knowledge of these mechanisms is important for several reasons: (1) Determining the bases of the code is an intrinsically interesting scientific problem involving integrated knowledge of mechanical, electrical, biological and chemical processes at organ, cellular, membrane, and molecular levels all focussed on understanding the role of the inner ear in hearing. (2) The results should have significance for sensory reception, in general, for mechanoreception in particular, and especially for understanding the acoustico-lateralis systems which include the lateral-line organs found in fish and amphibia as well as vestibular and auditory organs found in all vertebrates. (3) The practical benefits of this knowledge should also include more precise delineation of inner ear disorders, suggestions for treatment, development of prosthetic devices, and incorporation of knowledge of inner-ear processing into the design of systems for processing speech. The specific objective for the proposed grant period is to understand the mechanical processes in the cochlea that link sound-induced motion of the receptor organ to motion of its constituent structures, including the tectorial membrane, the hair bundles of hair cells, and the individual stereocilia that make up a hair bundle. The material properties (including osmotic, mechanical, and electrical properties) of the tectorial membrane will be measured in both isolated tectorial membrane preparations (in the mouse, chick, and the alligator lizard) and in an in vitro preparation of the alligator lizard cochlea. The relations among the sound-induced motion of the receptor organ, tectorial membrane, hair bundles of hair cells, and individual stereocilia in a hair bundle will be investigated using video microscopy of an in vitro preparation of the alligator lizard cochlea.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Research Project (R01)
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Hearing Research Study Section (HAR)
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Massachusetts Institute of Technology
Engineering (All Types)
Schools of Engineering
United States
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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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