SAIL Room, 111 Levin Building (425 S. University Ave.)
Department of Physics and Astronomy
Sensitivity and self-tuning in the auditory system
The inner ear constitutes a remarkable biological sensor that exhibits nanometer-scale sensitivity of mechanical detection. The first step in auditory processing is performed by hair cells, which act as transducers that convert minute mechanical vibrations into electrical signals that can be sent to the brain. This conversion involves the opening of ion channels, which are mechanically gated. The hair cells operate in a viscous environment, but can nevertheless sustain oscillations, amplify incoming signals, and even exhibit spontaneous motility. The thermodynamic requirements of this indicate the presence of an underlying active process that pumps energy into the system. Theoretical models have proposed that a hair cell constitutes a nonlinear system, and allow us to describe and predict how they respond to incoming sound.
Our experiments explore the physical mechanisms behind the detection of very weak signals, and describe them using models based on dynamical systems theory. We explore the different bifurcations that characterize hair bundle activity, and study how they affect phase-locking to incoming signals. We show that hair cell dynamics exhibit a very rich repertoire of behaviors, including multi-mode phase-locking, and signatures of chaos. Further, they can self-tune to different dynamic states, based on the strength of the applied signal, indicating the existence of an internal feedback mechanism. We show that theoretical models based on nonlinear dynamics can readily capture a broad range of our experimental findings.
The talk will begin at 12pm. A pizza lunch will be served at 11:45am.