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.
