Measurements and models of electrically-evoked motion in the gerbil organ of Corti

A cell with extraordinary motile ability exists in our inner ear, the outer hair cell. Outer hair cell (OHC) motility can occur at acoustic frequencies and play a key role in mammalian cochlear frequency selectivity and hearing sensitivity. To date, the mechanism of cochlear amplification is not well understood and remains a matter of controversy. In order to understand the role of OHC motility in cochlear micromechanics we developed a technique to measure the mechanical responses within the organ of Corti (OC) due to OHC forces. We used an excised cochlea preparation because it provided a good view of the organ and allowed us to compare the resulting responses of hundreds of cells simultaneously. The tissue was stimulated electrically using sinusoidal current, and the resulting motion was captured at specific phases within the stimulus period using stroboscopic video microscopy. Animations of this motion were created, and the displacement magnitude and phase for each structure were calculated using two dimensional cross-correlation. With these techniques we were able to detect displacements as low as ten nanometers. The frequency responses of electrically-evoked vibrations from the apical and middle turn had low pass filtering characteristics with cutoff frequencies near or below the estimated characteristic frequency of the imaging location. Using a simple one dimensional electrical model of our excised cochlea preparation, we hypothesize that the electrical properties of the stria vascularis play an important role in shaping the frequency response of individual structures.

Department dc:contributor.department

Harvard University--MIT Division of Health Sciences and Technology.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2002

Author dc:creator

• Karavitaki, Kiriaki Domenica, 1969-

Advisor dc:contributor.advisor

• David C. Mountain.

• Harvard University--MIT Division of Health Sciences and Technology.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/8087

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8087