Drs. Elizabeth Olson and Wei Dong, both from Columbia University, have studied how the cochlea amplifies and processes sounds. Their findings may lead to improved devices for better hearing.
A healthy ear has superior sound detecting and transmitting capabilities, compared to even the best hearing aid technology. Sound-sensing cells inside the cochlea, sensitive hair-like structures, vibrate strongly at different audio frequencies, depending on their location in the cochlea. To examine this behavior, Drs. Dong and Olson designed miniature sensors that simultaneously measure tiny pressure changes and cell-generated voltages at precise locations within the ears of test animals.
Pivoting cilia on a hair cell mechanically open ion channels in the cell membrane, allowing a small nerve current to flow, generating voltage. This sends a signal to nerve cells, relaying a certain sound frequency signal to the brain. Energy released by hair cell voltage feeds back to amplify the motion specific to that location’s frequency, driving additional movement of the local hair cells.
Drs. Dong and Olson found that a shift in the timing of this feedback voltage activates amplification at the right frequencies. With the shift, hair cells pump energy into cochlear motion, much like a child increases a swing’s motion by pumping her legs at the right time.
Modern hearing aids — which send amplified signals to the whole cochlea — can’t duplicate this location-based, frequency-specific amplification, and understanding how the cochlea accomplishes this could lead to major technological advances.
“Several groups are devising electromechanical cochlear prostheses and next-generation cochlear implants. A better understanding of the micro-mechanical machine of the ear’s cochlea will inform and guide these developments,” said Dr. Olson.
At Peninsula Hearing Center, we stress protecting the delicate natural mechanisms in your ear, and offer solutions for better hearing if those structures assistance.