Five decades of research on cochlear mechanics

Area of Science:

• Auditory Neuroscience
• Bioacoustics
• Biophysics

Background:

• Georg von Békésy's experiments on postmortem cochlear preparations revealed fundamental aspects of cochlear macromechanics.
• Early mathematical models explained Békésy's findings using surface wave hydrodynamics and identified experimental artifacts.

Purpose of the Study:

• To review Békésy's experiments and compare them with recent in vivo findings on cochlear frequency analysis.
• To propose a mechanism for enhanced cochlear frequency selectivity observed in vivo.

Main Methods:

• Review of historical experiments (Békésy's postmortem studies).
• Analysis of recent in vivo experimental data on cochlear mechanics.
• Mathematical modeling of hair-cell stereocilia resonance.

Main Results:

• In vivo experiments reveal sharper cochlear frequency analysis than Békésy's observations.
• A two-stage interacting model for cochlear frequency analysis is proposed.
• Resonance of hair-cell stereocilia, influenced by the tectorial membrane, is suggested as a key factor.

Conclusions:

• The tectorial membrane's mass loading on stereocilia may enable resonance, enhancing frequency selectivity.
• This resonance could alter the mechanical system of the basilar membrane and organ of Corti from a second-order to a fourth-order system.