The middle ear plays a vital role in the sense and sensitivity of hearing, yet there is currently a lack of knowledge about the mechanisms of high-frequency middle-ear sound transmission in mammals. The overall goal of this project is to understand the relationships between the morphometry of the middle ear and the biomechanical processes that lead to physiological and clinical responses. The approach is to deconstruct the middle ear into subsystems that are each characterized by morphological and physiological measurements, as well as three-dimensional linear and nonlinear mathematical analyses. The subsystems are then mathematically reassembled to form a complete `virtual middle-ear'model that can be used to examine issues relevant to high frequency sound transmission in a variety of animals and repaired middle ears before and after surgery.
Specific Aim #1 : At high frequencies, experimental evidence suggests that sound conduction is not limited by the inertia of the middle-ear bones, contrary to expectations. Recent moment of inertia calculations suggest that the malleus switches from a hinging motion at low frequencies to a new twisting motion at high frequencies, in order to take advantage of the reduced inertia associated with a twisting type of motion. It is hypothesized that the mobile saddle-shaped malleus-incus joint is able to suitably transfer this twisting motion to the incus. This will be tested using micro-CT imaging, cryogenic transmission electron microscopy, optical second harmonic generation, hinging and twisting motion measurements with a laser Doppler vibrometer, and bio-computational modeling.
Specific Aim #2 : The human middle-ear cavity is known to be an irregularly shaped space within the temporal bone that varies from person to person. A finite element modeling approach will be used to test the hypothesis that the complex shape of the human middle-ear cavity functions to break up resonant modes that would otherwise decrease hearing sensitivity at specific resonant frequencies. The finite element approach, which is well-suited for the nonlinear descriptions needed to incorporate the forces exerted by the tensor tympani and the stapedius muscles, will also be used to understand how these muscles affect sound transmission through the middle ear.
Specific Aim #3 : Ear surgeons target restoration of hearing in the speech frequency range, and not in the higher frequencies where important sound localization cues are known to reside. Temporal bone measurements and the anatomically- and physics-based virtual middle-ear model will be used to understand how to improve high-frequency outcomes of middle-ear surgical treatments, such as tympanic membrane repair (myringoplasty) and ossicle replacement with a prosthesis (tympanoplasty).
Specific Aim #4 : Our hypothesis that myringoplasty and tympanoplasty surgery patients continue to have air-bone gap deficits at frequencies above 4 kHz will be tested. New methods to measure bone conduction sensitivity will be developed for high frequencies and combined with existing air conduction measurement methods. While it is well accepted that amongst terrestrial vertebrates, the mammalian middle ear is unique in its ability to transmit sounds from the external world to the cochlea for frequencies above 10 kHz, the biomechanical basis for sound transmission at high frequencies is poorly understood, which has consequences in the clinical realm. It is well known that the morphometry of the middle ear plays a key role in sound transmission, but the lack of knowledge about the relationships between middle-ear structures and sound transmission has resulted in unsatisfactory and variable outcomes of middle-ear repairs, particularly at high frequencies where sound localization cues may be important for hearing in noisy situations. The proposed studies will provide a solid scientific foundation for understanding the structural basis of middle-ear sound transmission, leading to clinical applications for the surgical reconstruction of the middle ear, the interpretation of otoacoustic emissions, and improvements to the understanding of passive and active prostheses used by surgeons to repair the middle ear.

Public Health Relevance

While it is well accepted that amongst terrestrial vertebrates, the mammalian middle ear is unique in its ability to transmit sounds from the external world to the cochlea for frequencies above 10 kHz, the biomechanical basis for sound transmission at high frequencies is poorly understood, which has consequences in the clinical realm. It is well known that the morphometry of the middle ear plays a key role in sound transmission, but the lack of knowledge about the relationships between middle-ear structures and sound transmission has resulted in unsatisfactory and variable outcomes of middle-ear repairs, particularly at high frequencies where sound localization cues may be important for hearing in noisy situations. The proposed studies will provide a solid scientific foundation for understanding the structural basis of middle-ear sound transmission, leading to clinical applications for the surgical reconstruction of the middle ear, the interpretation of otoacoustic emissions, and improvements to the understanding of passive and active prostheses used by surgeons to repair the middle ear.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC005960-07
Application #
8214658
Study Section
Auditory System Study Section (AUD)
Program Officer
Watson, Bracie
Project Start
2009-02-17
Project End
2014-01-31
Budget Start
2012-02-01
Budget End
2013-01-31
Support Year
7
Fiscal Year
2012
Total Cost
$324,167
Indirect Cost
$120,524
Name
Stanford University
Department
Engineering (All Types)
Type
Schools of Engineering
DUNS #
009214214
City
Stanford
State
CA
Country
United States
Zip Code
94305
Kim, Namkeun; Steele, Charles R; Puria, Sunil (2014) The importance of the hook region of the cochlea for bone-conduction hearing. Biophys J 107:233-41
Cho, Jin-Ho; Puria, Sunil; Gummer, Anthony W (2013) MEMRO 2012 - Middle-ear bridge between science and otology. Hear Res 301:2-3
Kim, Namkeun; Steele, Charles R; Puria, Sunil (2013) Superior-semicircular-canal dehiscence: effects of location, shape, and size on sound conduction. Hear Res 301:72-84
Shimizu, Yoshitaka; Puria, Sunil; Goode, Richard L (2011) The floating mass transducer on the round window versus attachment to an ossicular replacement prosthesis. Otol Neurotol 32:98-103
Puria, Sunil; Steele, Charles (2010) Tympanic-membrane and malleus-incus-complex co-adaptations for high-frequency hearing in mammals. Hear Res 263:183-90
Popelka, Gerald R; Telukuntla, Goutham; Puria, Sunil (2010) Middle-ear function at high frequencies quantified with advanced bone-conduction measures. Hear Res 263:85-92
Sim, Jae Hoon; Puria, Sunil (2009) A 3-D Force and Moment Motor for Small-Scale Biomechanics Experiments. IEEE Sens J 9:1924-1932
Homma, Kenji; Du, Yu; Shimizu, Yoshitaka et al. (2009) Ossicular resonance modes of the human middle ear for bone and air conduction. J Acoust Soc Am 125:968-79
Tuck-Lee, James P; Pinsky, Peter M; Steele, Charles R et al. (2008) Finite element modeling of acousto-mechanical coupling in the cat middle ear. J Acoust Soc Am 124:348-62
Sim, Jae Hoon; Puria, Sunil (2008) Soft tissue morphometry of the malleus-incus complex from micro-CT imaging. J Assoc Res Otolaryngol 9:5-21

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