Ossicular Mechanics of a Low Frequency Ear and Implications for Bone-Conducted Hearing.

低频耳的听骨力学及其对骨传导听力的影响。

• 批准号: 10594482
• 负责人: Caitlin O'Connell-Rodwell
• 金额: $ 14.18万
• 依托单位: MASSACHUSETTS EYE AND EAR INFIRMARY
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-04-01 至 2025-03-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10594482
• 关键词: 3-Dimensional; Affect; Air; Anatomy; Articulation; Auricular prosthesis; Bone Conduction; Characteristics; Cochlea; Detection; Drowning; Ear; Elephants; Exhibits; External auditory canal; Food; Frequencies; Goals; Head Movements; Hearing; Hearing Aids; Hearing Tests; Human; Image; Impulsivity; Incus; Investigation; Jaw; Joints; Labyrinth; Lasers; Malleus; Mammals; Mastication; Measurement; Measures; Mechanics; Methods; Modeling; Modification; Morphology; Motion; Noise; Ossicular Replacement Prosthesis; Performance; Play; Promontory; Prosthesis; Role; Rotation; Series; Shapes; Source; Stapes; Structure-Activity Relationship; Temporal bone structure; Testing; Time; Tympanic membrane; animation; bone; comparative; cranium; design; flexibility; hearing impairment; improved; insight; middle ear; novel; pressure; reconstruction; response; sound; sound frequency; structural determinants; transmission process; vibration

Abstract The mammalian ear contains three middle-ear bones called ossicles that transmit both air-conducted (AC) sound from the eardrum to the inner ear and bone-conducted (BC) vibrations of the skull to the inner ear. The functional significance of having three ossicles to transmit sound is not completely understood, yet their varied shapes, mass distributions, and articulation around two flexible joints could serve to protect the inner ear from static pressure and impulsive AC sounds presented in the ear canal, and could reduce sensitivity to potentially distracting self-generated BC vibrations caused by head movement, chewing, etc. At the same time, ossicles might also improve AC and BC hearing at low frequencies. In this study, we propose to test the role that ossicular shape, mass and mass distribution, as well as flexibility play on 3D ossicular motion and sound transmission into the cochlea for both human and elephant temporal bones in response to AC and BC stimulation under normal and modified conditions. Despite significant anatomical differences, humans and elephants exhibit very similar audiograms over their overlapping 20 Hz–11 kHz frequency range, although elephants can hear below 20 Hz and humans can hear above 11 kHz. Middle-ear bones scale with skull size, such that elephant ossicles (the largest among terrestrial mammals) are approximately seven times heavier than those of humans. Studies suggest that BC hearing is enhanced below 100 Hz using mass-loading to simulate greater ossicular mass, and our preliminary measurements on elephants suggest that their heavier ossicles should yield an order of magnitude better BC hearing than humans at low frequencies. BC hearing in elephants might also be enhanced due to what appears to be a partially fused incudo-malleolar joint. Thus, quantifying the structure–function relationships and mass loading within human versus elephant ears could improve our understanding of the possible optimizations and trade-offs within the middle ear. The immediate goal of this investigation is to quantitatively compare human and elephant ossicular-chain morphology and motion as it relates to input to the cochlea by measuring ossicular shape and mass distributions using µCT imaging; and measuring 3D ossicular motions in response to AC and BC stimulation using 3D laser Doppler vibrometry, for the normal and modified cases with added mass and reduced ossicular-joint flexibility. The motion measurements will be used to animate µCT reconstructions of the ossicles, and these results will be compared using moments of inertia (MOI) to quantify the functional implications of the inter-species structural differences and effects of modifications in terms of: 1) sound transmission from the ear canal to the cochlea, especially at lower frequencies; 2) the relative motion of the ossicles; and 3) the transmission of sound via bone conduction. The structure–function relationships revealed through this inter-species comparison may have ramifications in the design of specialized passive and active middle-ear prosthetic devices for restoring human hearing.

摘要 哺乳动物的耳朵包含三个中耳骨称为听小骨，传输空气传导（AC） 从鼓膜到内耳的声音和从颅骨到内耳的骨传导（BC）振动。的 具有三个听小骨来传递声音的功能意义尚未完全理解，但它们的 不同的形状、质量分布和围绕两个柔性接头的铰接可以用来保护内部 耳道内的静态压力和脉冲交流声，并可降低敏感性， 头部运动、咀嚼等可能会分散自身产生的BC振动。同时 同时，听小骨也可能改善低频AC和BC听力。在这项研究中，我们建议测试 听骨形状、质量和质量分布以及柔韧性对听骨三维运动的作用， 人类和大象颞骨对AC和BC的耳蜗声传输反应 在正常和修改条件下的刺激。尽管存在显著的解剖学差异，人类和 大象在重叠的20 Hz-11 kHz频率范围内表现出非常相似的听力图， 大象可以听到20赫兹以下的声音，而人类可以听到11千赫以上的声音。中耳骨与头骨大小成比例， 大象的听小骨（陆地哺乳动物中最大的）大约重七倍 比人类的要多。研究表明，BC听力在100 Hz以下使用质量负荷增强， 模拟更大的听骨质量，我们对大象的初步测量表明， 听小骨在低频率下应产生比人类好一个数量级的BC听力。BC听证会 大象也可能是增强由于什么似乎是一个部分融合砧踝关节。因此，在本发明中， 量化人与大象耳朵的结构-功能关系和质量负荷， 提高我们对中耳内可能的优化和权衡的理解。立即 本研究的目的是定量比较人类和大象的听骨链形态， 通过使用µCT测量听骨形状和质量分布， 使用3D激光多普勒测量响应于AC和BC刺激的3D听骨运动 振动测量法，用于正常和改良病例，增加了质量，降低了听小骨关节的灵活性。的 运动测量将用于制作听小骨的µCT重建动画，这些结果将 使用惯性矩（MOI）进行比较，以量化物种间结构的功能影响 在以下方面的修改的差异和效果：1）从耳道到耳蜗的声音传输， 特别是在较低的频率下; 2）听小骨的相对运动;以及3）声音通过 骨传导通过这种种间比较揭示的结构-功能关系可能 在设计专门的被动和主动中耳假体装置以恢复 人类听觉