This project is a collaboration using computational, theoretical, and experimental approaches to analyze early events in hearing, at various scales ranging from the motion of hair bundles to neural coding in the auditory nerve. The recent focus of the collaboration has been the active process that injects mechanical energy into the cochlea to assist the mechanical amplification of signals, in particular the hypothesis that the active process poises the organ's elements at the threshold of an oscillatory instability, called a Hopf bifurcation. The current focus extends to examine the interaction of the active process with its environment: adaptive mechanisms, other elements, and downstream processing. At the microscopic scale the environment of the active process consists of the adaptation mechanisms that regulate it and keep it poised, and detailed analysis of various candidate mechanisms is proposed. At the mesoscopic scale the environment includes other nearby active elements: the focus will be the interactions between hair cells in the whole cochlea, and the mechanism and process through which the dynamical behavior of each hair cell contributes to the overall function of the cochlea without a massive cacophony of feedback oscillations. The outcome would be a theory of what the observed responses should be, given the microscopic model. At the coarsest level the encoding of the auditory stream into the acoustic nerve will be studied, particularly how level-independent auditory percepts can be extracted from the level-dependent responses of the cochlea. Elucidation of the dynamical principles of cochlea behavior would likely guide newer generations of cochlear implants, aid in the design of pharmacological intervention, and help understand whether the ear's amplifies can be protected or recovered from damage. Similarly, elucidation of the principles of auditory neural coding should provide deeper guiding principles for voice recognition and other technology to assist the hearing impaired.
