STANFORD MECHANICAL ENGINEERS DEVELOP NEW TECHNOLOGY TO STUDY HEARING

Stanford researchers have developed a tiny moving probe to study the mechanical properties of sensory cells in the ear. Their work could lead to new treatments for hearing loss, and the probe may advance other scientists’ research as well.

Much of what is known about sensory touch and hearing cells is based on indirect observation. Scientists know that these exceptionally tiny cells are sensitive to changes in force and pressure. But to truly understand how they function, scientists must be able to manipulate them directly. Now, Stanford scientists are developing a set of tools that are small enough to stimulate an individual nerve or group of nerves but also fast and flexible enough to mimic a realistic range of forces.


A team of mechanical engineers from the Stanford School of Engineering and ear specialists from the Stanford School of Medicine is developing a new device, known as a force probe, that allows the researchers to study the flexible hair cells that translate sound waves into electrical signals. The probe works at a range of frequencies that are more realistic to human hearing than previous machines.

Our ability to interpret sound is largely dependent on bundles of thousands of tiny hair cells that get their name from the hair-like projections on their top surfaces. As sound waves vibrate the bundles, they force proteins in the cells' surfaces to open and allow electrically charged molecules, called ions, to flow into the cells. The ions stimulate each hair cell, allowing it to transfer information from the sound wave to the brain. Hair bundles are more sensitive to particular frequencies of sound, which allows us to tell the difference between a siren and a subwoofer.

People with damaged or congenital defects in these delicate hair cells suffer from severe, irreversible hearing loss. Scientists remain unsure how to treat this form of hearing loss because they do not know how to repair or replace a damaged hair cell. Physical manipulation of the cells is key to exploring the fine details of how they function. This new probe is the first tool nimble enough to do it. Beth Pruitt, an associate professor of mechanical engineering , and researchers in her Stanford Microsystems Lab have been working to develop electromechanical devices for use as high-speed force probes. The tool, developed with funding from Stanford's Bio-X program , vibrates the hair cells to mimic the effect of incoming sound waves. This allows the researchers to study the cause-and-effect relationships between the forces exerted in hair cells by sound waves and the electrical signals they produce in response.

Source: Stanford University