Does Human Ossicular Joint Flexibility Filter Damaging Input to the Cochlea?

描述(申请人提供)：中耳的作用是将压力波从周围环境传递到充满液体的耳蜗里。虽然非哺乳动物的中耳通常使用一个相对简单的活塞状骨骼来实现这一点，但哺乳动物的中耳是独特的，因为它包含三个不同的骨骼(听骨由韧带和肌腱悬挂在中耳腔内)--锤骨、砧骨和砧骨。在人类和其他哺乳动物中，这些听小骨通过两个滑膜关节相连，每个关节都有一块肌肉连接到锤骨和距骨上。由于这种中耳设计在简单的听小骨屈曲之外引入了额外的灵活性，因此它传递的振动可能会更少。 比融合系统更高效。那么，为什么人类会进化出这种复杂而灵活的中耳结构呢？对中耳柔韧性的深入了解，既可以加深科学知识，又可以为量化中耳病变的影响提供依据。它还将为改进的中耳假体的设计奠定框架，特别是因为目前许多柱状装置消除了健康人类中耳存在的大部分灵活性。这里提出的中心假设是，人类中耳活动关节所赋予的灵活性通过减少脉冲刺激对耳蜗组织的峰值输入并允许两个中耳肌肉在持续噪声期间减少对耳蜗组织的传递来保护耳蜗结构，并且这种灵活性优势并不是以对通过中耳向耳蜗组织的正常声音传递的过度不利影响为代价的。这一中心假设将通过1)比较正常人类听骨链的3D运动测量结果与由于一个或两个听骨关节融合或植入商业上可买到的小柱型假体而导致灵活性降低的改良版本的测量结果，以及2)使用新的、经过实验验证的人类中耳关节和肌肉的计算模型来检验。这项提议完成后，将有助于我们科学地理解灵活性对人类耳朵的保护作用，并将提供一种新的中耳计算模型。 除了对研究中耳灵活性有用外，该模型还将有利于未来的研究工作，例如通过为设计更有效的中耳假体和手术干预提供试验台。

DESCRIPTION (provided by applicant): The purpose of the middle ear is to transmit pressure waves from the environment into the fluid-filled cochlea. While non-mammalian middle ears typically achieve this using a single relatively simple piston-like bone, the mammalian middle ear is unique in that it contains three distinct bones (ossicles)-the malleus, incus, and stapes-suspended within the middle-ear cavity by ligaments and tendons. In humans, among other mammals, these ossicles are connected via two synovial joints, and one muscle each is attached to the malleus and the stapes. Since this middle-ear design introduces additional flexibility beyond simple flexion of the ossicles, it might be expected to transfer vibrations less efficiently than a fused system. Why, then, have humans evolved this complicated and flexible middle-ear structure? An in-depth understanding of middle-ear flexibility will both further scientific knowledge and provide a basis for quantifying the effects of middle-ear pathologies. It will also lay a framework for the design of improved middle-ear prostheses, especially since many of the current columella-like devices remove much of the flexibility present in the healthy human middle ear. The central hypothesis proposed here is that the flexibility imparted by mobile joints in the human middle ear protects cochlear structures by reducing the peak input to the cochlea from impulsive stimuli and by allowing the two middle-ear muscles to reduce transmission to the cochlea during periods of sustained noise, and that this flexibility advantage does not come at the cost of an excessive adverse effect on normal sound transmission through the middle ear to the cochlea. This central hypothesis will be tested by 1) comparing 3D motion measurements of the normal human ossicular chain against measurements of modified versions with reduced flexibility due to fusing one or both ossicular joints or due to implanting a commercially available columella-type prosthesis, as well as through 2) the use of new, experimentally validated computational model of the human middle-ear joints and muscles. When completed, this proposal will contribute to our scientific understanding of the protective role of flexibility in the human ear, and will provide a new computational model of the middle ear. In addition to its usefulness for studying middle-ear flexibility, this model will also benefit futre research efforts, such as by providing a test bed for the design of more-effective middle-ear prostheses and surgical interventions.