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: 10378136
• 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 2024-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10378136
• 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; Lead; 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; base; bone; comparative; cranium; design; flexibility; hearing impairment; improved; insight; middle ear; novel; pressure; reconstruction; response; sound; sound frequency; 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.

抽象的 哺乳动物的耳朵包含三个称为Ossicle的中耳骨头，它们传输了两个空气传导（AC） 从耳朵到内耳的声音，颅骨振动到内耳。这 尚不完全理解有三个发射声音的功能意义 在两个柔性关节周围的各种形状，质量分布和铰接都可以用来保护内部 耳道中呈现的静压和冲动的AC声音的耳朵，可以降低对 有可能分散由头部移动，咀嚼等引起的自我生成的BC振动。 时间，耳塞还可以在低频下改善AC和BC听证会。在这项研究中，我们建议测试 骨形状，质量和质量分布以及3D骨运动和灵活性发挥的作用 响应AC和BC的人类和大象临时骨骼中的声音传播到耳蜗中 在正常和修改条件下刺激。尽管有很大的解剖学差异，人类和 大象在重叠的20 Hz – 11 kHz频率范围内暴露了非常相似的听力图，尽管 大象可以听到以下20 Hz，人类可以听到以上11 kHz的声音。中耳骨头尺度有头骨大小， 这样的大象小骨（陆地哺乳动物中最大）大约重七倍 比人类的人。研究表明，使用质量加载到 模拟更大的骨质质量，我们对大象的初步测量表明它们较重 在低频下，小骨的听力应比人类更好。卑诗省听证会 由于似乎是部分融合的牙齿麦麦乳肌关节，大象也可能会增强。那， 量化人与大象耳朵内的结构 - 功能关系和质量负荷可以 提高我们对中耳内可能的优化和权衡的理解。直接 这项投资的目标是定量比较人和大象的骨骨链形态和 通过使用µCT测量骨形状和质量分布，它与对耳蜗的输入有关 成像；并使用3D激光多普勒对AC和BC刺激的响应测量3D骨运动 振动法，对于正常和改良的病例，质量增加，骨关节柔韧性降低。这 运动测量将用于动画Ossicles的µCT重建，这些结果将为 使用惯性矩（MOI）进行比较来量化物种间结构的功能含义 修饰的差异和影响：1）从耳道到耳蜗的声音传播， 特别是在较低的频率下； 2）骨的相对运动； 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的中耳假体设备的设计中，恢复有影响力 人类的听力。