Tuning, sensitivity, and nonlinear dynamics in systems of coupled hair cells

就潜在的生物物理机制而言，听觉仍然是最不为人所知的感官之一。为了对极微弱的声音敏感，听觉系统必须在与原子尺寸相当的尺度上探测到运动。这涉及到毛细胞——一种特殊的细胞，它从传入的声波中检测机械信号，并将其转换成电信号发送到大脑。本研究将测量毛细胞的运动，以验证毛细胞之间的耦合是实现这种听觉敏感性的重要因素的假设，并探索同步在整个器官敏感性中的作用。青蛙和蜥蜴的内部听觉器官将被放置在合适的化学环境中，它们的运动图像将被高速摄像机捕捉到。通过平行观察多个毛细胞的运动，就有可能看到它们是否在一起运动。额外的测量将测试耦合系统是否显示出不随信号线性增长的响应。最后，不同种类的器官之间的比较研究，显示出非常不同的几何形状，将确定不同数量的耦合如何影响整体性能。预测是，毛发束之间的同步将增强内耳的灵敏度和调谐。如果这是真的，这将有助于解释听觉的纳米级灵敏度，这是感觉神经科学中长期悬而未决的问题之一。该项目将为本科生和高中生提供教育机会，让他们参与高度跨学科的科学项目。

The sense of hearing remains one of the least understood of the senses, in terms of the underlying biophysical mechanisms. To be sensitive to extremely faint sounds, the auditory system must detect movements at a scale comparable to atomic dimensions. This involves hair cells--specialized cells that detect mechanical signals from incoming sound waves and convert them into electrical signals sent to the brain. This research will measure movements of hair cells to test the hypothesis that coupling between hair cells constitutes an important factor in achieving this auditory sensitivity and to explore the role of synchronization in the sensitivity of the whole organ. Internal auditory organs from the frog and the lizard will be placed in appropriate chemical environments, and images of their movements will be captured with a high-speed camera. By observing the motion of multiple hair cells in parallel, it will be possible to see if they move in unison. Additional measurements will test whether the coupled system shows a response that does not grow linearly with the signal. Finally, comparative study between organs of different species, which show very different geometry, will determine how different amounts of coupling affect the overall performance. The prediction is that synchronization among hair bundles will enhance both the sensitivity and tuning in the inner ear. If true, this will help to explain the nanoscale sensitivity of hearing, one of the long-open problems in sensory neuroscience. The project will provide educational opportunities for undergraduate and high school students, by involving them in highly interdisciplinary science projects.