Physics Colloquium - Elizabeth Olson, Columbia University - "Amplification of Sound in the Mammalian Cochlea"
The snail-shaped mammalian cochlea houses a narrow strip of sensory tissue that separates compartments of salty water. Sound stimulation launches a mechanical traveling wave down the cochlea that peaks in a tonotopic manner: high/low frequencies peak in the cochlear base/apex. Sensory hair cells respond to the motion with intracellular current and voltage. In outer hair cells the electrical response elicits mechanical forces, by means of piezoelectric “prestin” proteins in the cell membrane. These forces augment the motion of the sensory tissue, boosting and sharpening the mildly frequency-resolved pattern of motion that obtains in the passive (dead) cochlea. The motion is increased by a factor of 100 or more for low sound pressure level sounds and very little for high level sounds, thus active cochlear mechanics is compressively nonlinear. Our work explores the dynamics of cochlear amplification in-vivo, using micro-pressure and voltage sensors and laser interferometry. Our recent results detect power amplification in the cochlea and inform the mechanism that gives rise to the localized sharpening of cochlear responses that is fundamental to normal hearing.
Location: Jadwin A10
Date/Time: 11/29/12 at 4:30 pm - 11/29/12 at 5:30 pm
Category: Physics Colloquium