Mechanical Responses of the Organ of Corti to Acoustic and Electrical Stimulation in Vitro

¹ Rockefeller University

^* To whom correspondence should be addressed. E-mail: hudspaj{at}rockefeller.edu.

Submitted on July 13, 2005
Revised on August 12, 2005
Accepted on 8 September 2005

	Abstract

The detection of sound by the cochlea involves a complex mechanical interplay among components of the cochlear partition. An in vitro preparation of the second turn of the jird's cochlea provides an opportunity to measure cochlear responses with subcellular resolution under controlled mechanical, ionic, and electrical conditions that simulate those encountered in vivo. Using photodiode micrometry, laser interferometry, and stroboscopic video microscopy, we have assessed the mechanical responses of the cochlear partition to acoustic and electrical stimuli near the preparation's characteristic frequency. Upon acoustic stimulation, the partition responds principally as a rigid plate pivoting around its insertion along the spiral lamina. The radial motion at the reticular lamina greatly surpasses that of the tectorial membrane, giving rise to shear that deflects the mechanosensitive hair bundles. Electrically evoked mechanical responses are qualitatively dissimilar from their acoustically evoked counterparts and suggest the recruitment of both hair bundle- and soma-based electromechanical transduction processes. Finally, we observe significant changes in the stiffness of the cochlear partition upon tip-link destruction and tectorial-membrane removal, suggesting that these structures contribute considerably to the system's mechanical impedance and that hair bundle-based forces can drive active motion of the cochlear partition.

Key Words: Amplification, Auditory system, Basilar membrane, Cochlea, Hair cell, Mechanoelectrical transduction

This article has been cited by other articles:

				D. N. Furness, S. Mahendrasingam, M. Ohashi, R. Fettiplace, and C. M. Hackney The Dimensions and Composition of Stereociliary Rootlets in Mammalian Cochlear Hair Cells: Comparison between High- and Low-Frequency Cells and Evidence for a Connection to the Lateral Membrane J. Neurosci., June 18, 2008; 28(25): 6342 - 6353. [Abstract] [Full Text] [PDF]

				M. Drexl, M. M. Mellado Lagarde, J. Zuo, A. N. Lukashkin, and I. J. Russell The Role of Prestin in the Generation of Electrically Evoked Otoacoustic Emissions in Mice J Neurophysiol, April 1, 2008; 99(4): 1607 - 1615. [Abstract] [Full Text] [PDF]

				M. Beurg, J.-H. Nam, A. Crawford, and R. Fettiplace The Actions of Calcium on Hair Bundle Mechanics in Mammalian Cochlear Hair Cells Biophys. J., April 1, 2008; 94(7): 2639 - 2653. [Abstract] [Full Text] [PDF]

				J. Ashmore Cochlear Outer Hair Cell Motility Physiol Rev, January 1, 2008; 88(1): 173 - 210. [Abstract] [Full Text] [PDF]

				I. Tomo, J. Boutet de Monvel, and A. Fridberger Sound-Evoked Radial Strain in the Hearing Organ Biophys. J., November 1, 2007; 93(9): 3279 - 3284. [Abstract] [Full Text] [PDF]

				M. E. Chiappe, A. S. Kozlov, and A. J. Hudspeth The Structural and Functional Differentiation of Hair Cells in a Lizard's Basilar Papilla Suggests an Operational Principle of Amniote Cochleas J. Neurosci., October 31, 2007; 27(44): 11978 - 11985. [Abstract] [Full Text] [PDF]

				K. D. Karavitaki and D. C. Mountain Imaging Electrically Evoked Micromechanical Motion within the Organ of Corti of the Excised Gerbil Cochlea Biophys. J., May 1, 2007; 92(9): 3294 - 3316. [Abstract] [Full Text] [PDF]

				R. Fettiplace Active hair bundle movements in auditory hair cells J. Physiol., October 1, 2006; 576(1): 29 - 36. [Abstract] [Full Text] [PDF]