Investigating the hair-bundle state space in an exploration of inner ear tuning

描述(申请人提供)：噪音引起的、药物引起的和先天性听力损失是由于内耳的感觉感受器毛细胞受损造成的。75岁以上的美国人中有一半患有中度至重度听力障碍，全球年轻人听力障碍的患病率也在上升，听力损失是一个重大的公共卫生问题。了解毛细胞的正常运作--包括它的机械天线和发束--将有助于理解听力损失的病理生理学，并开发治疗方法。这项拟议的研究试图检查发束的动力学特性，这是其放大机械刺激能力的基础。作为一名 在动力学系统中，发束的活动可以通过描述发束在各种条件下的行为的状态空间来表征。状态空间中包括Hopf分叉，这是一种不稳定性，使发束具有在临界点附近进行自我调整的能力。通过控制偏移力和刚度这两个控制参数，可以很容易地研究这个动力系统。我将尝试强迫发束越过其临界点，第一次演示嵌入发束力学中的Hopf分叉的存在。这一演示将为进一步研究听觉活动过程中特有的现象提供一个工具。因此，通过控制机械特性，我将阐明赋予人类高度分辨听觉感觉的发束的功能。

DESCRIPTION (provided by applicant): Noise-induced, drug-induced, and congenital hearing loss results from damage to hair cells, the sensory receptors of the inner ear. With half of Americans over 75 afflicted by moderate to severe hearing impairment and a worldwide rise in the prevalence of hearing impairment in younger adults, hearing loss is a significant public-health concern. Knowledge of the normal operation of the hair cell-including that of its mechanical antenna, the hair bundle-will contribute to understanding the pathophysiology of hearing loss and developing treatments for it. The proposed study seeks to examine the dynamical properties of a hair bundle that underlie its ability to amplify mechanical stimuli. As a dynamical system, the activity of a hair bundle can be characterized by a state space that describes the bundle's behavior under various conditions. Included in the state space is a Hopf bifurcation, an instability that endows the hair bundle with the ability to self-tune near criticalty. This dynamical system can be readily explored by manipulation of two control parameters, offset force and stiffness. I will attempt to coerce the hair bundle to cross its critical point, demonstrating for the first time the presence of a Hopf bifurcation embedded in hair-bundle mechanics. This demonstration will provide a tool for further investigation of phenomena characteristic of the active process in hearing. Thus, by controlling mechanical properties, I shal elucidate the functions of hair bundles that endow humans with highly resolved auditory sensation.