STRUCTURE-FUNCTION RELATIONS IN MIDDLE EARS

这项工作的长期目标是了解 外耳和中耳的结构及其在 听觉信号传输 方法是测量声学 性能是选定的物种，不同的听觉结构和 构建分析模型，其中结构构件 在机械元件的网络中明确地表示。 从 这些测量和模型结构的一般规则- 函数关系的推导。 在目前的赠款期间，注意力集中在猫， 蜥蜴 在cat测量的性质的外部和 中耳已经决定了这些部分的性能， 耳朵作为收集器和发射器的声音功率的内耳。 对蜥蜴的研究表明， 声音主要进入耳朵，尽管耳道必须 修改;通过大面积的辅助声音通路 蜥蜴的皮肤也能有效地将声音传到中耳 在低频率。 对猫和 蜥蜴表明鼓膜有明显的 不同的声学特性;在高频下，cat TM 而蜥蜴TM是块状的。 这些结果表明， 存在于将声音刺激耦合到鼓膜的过程中， 膜运动 这里提出的项目集中在 这些过程以及这些过程中的变化的结构基础 在不同的脊椎动物类之间的过程。 三个领域将 检查：1）哺乳动物外耳的性能， 既作为声功率的收集器又作为 关于声源位置的信息，将被研究 通过测量那些外耳 有趣的结构相似性和差异。 （二） 中耳的辅助通路将在蜥蜴中进行研究， 鸡，也在一些哺乳动物（猪和羊），其中 鼓膜结构不同于猫，豚鼠， 人类 在猪和羊中， 鼓膜是松弛的而不是伸展的。 我们将 探索这个“松弛部”作为一个 中耳旁道 3)的关系 猫、豚鼠、 猪，龙猫，鳄鱼蜥蜴，鸡将被研究 通过测量他们的“机械Transformer” 特性. 由于鼓膜在 产生中耳的类似变压器的特性， 其结构在脊椎动物中变化很大，规格 TM的结构-功能关系是关键。 从这项工作中获得的对声音接收的理解 对听力学家诊断听力障碍有一定的实际意义。 传导性听力障碍和耳科医生在手术 耳朵畸形的矫正。

The long-term goal of this work is to understand the relationship the structure of external and middle ears and their function in auditory signal transmission. The approach is to measure acoustic performance is selected species that vary in aural structure and to construct analytical models in which structural components are explicitly represented in networks of mechanical elements. From these measurements and models general rules for structure- function relations are derived. During the current grant period attention was focused on cat and lizard. In cat measurements of the properties of the external and middle ear have determined the performance of these parts of the ear as collectors and transmitters acoustic power to the inner ear. The lizard studies have shown that the usual presumption that sound enters the ear primarily though the ear canal must be modified; accessory sound pathways through large areas of the lizard's skin also couple sound to the middle ear, most effectively at low frequencies. Comparison of the measurements on cat and lizard shows that the tympanic membranes have distinctly different acoustic properties; at high-frequencies the cat TM is resistive whereas the lizard TM is masslike. These results suggest that substantial interspecies differences exist in the processes that couple acoustic stimuli into tympanic- membrane motion. The projects proposed here are focused on these processes and on the structural basis of variations in these processes among different vertebrate classes. Three areas will be examined: 1) The performance of the mammalian external ear, both as a collector of acoustic power and as a source of information about the location of sound sources, will be studied through measurements in species whose external ears have interesting structural similarities and and differences. 2) Accessory pathways to the middle ear will be studied in lizard, chicken, and also in some mammals (pig and sheep) in which the tympanic-membrane structure differs from cat, guinea pig, and human. In pigs and sheep a large structurally-distinct section of the tympanic membrane is flaccid rather than stretched. We will explore the hypothesis that this "pars flaccida" functions as an accessory pathway to the middle ear. 3) The relationship between structure and function of the tympanic membranes of cat, guinea, pig, chinchilla, alligator lizard, and chicken will be studied through measurements of their "mechanical transformer" properties. Since the tympanic membrane plays a key role in producing the transformer-like properties of the middle ear and its structure varies dramatically among vertebrates, specification of the TM's structure-function relations is key. The understanding of sound reception that results from this work will be of practical significant to audiologists in the diagnosis of conductive hearing disorders and to otologists in the surgical correction of abnormalities of the ear.