Von Békésy and cochlear mechanics

Abstract

Georg Békésy laid the foundation for cochlear mechanics, foremost by demonstrating the traveling wave that is the substrate for mammalian cochlear mechanical processing. He made mechanical measurements and physical models in order to understand that fundamental cochlear response. In this tribute to Békésy we make a bridge between modern traveling wave observations and those of Békésy, discuss the mechanical properties and measurements that he considered to be so important, and touch on the range of computational traveling wave models.

Fig. 1

Guinea pig tonotopic map from Békésy's BM displacement measurements and the same data shifted up 0.5 octave, compared to Greenwood's tonotopic map determined with AN recordings coupled to anatomical staining. Also shown is a theoretical estimate of the passive peak location using Békésy's BM compliance measurement.

Fig. 2

BM displacement measured by Békésy in human, at four points of the stimulus cycle.

Fig. 3

BM velocity measured by Ren in gerbil. Amplitude and phase data are combined to give the response pattern at six points within half a stimulus cycle.

Fig. 4

Auditory nerve responses measured by Van der Heijden and Joris in the cat, and their analysis to find traveling wave patterns. (A) Response amplitudes from nine ANs as a function of frequency and (B) corresponding phases. (C) Each curve shows phase for stimulation at one frequency as a function of location, and is derived from data in B. The phase versus location response for 1 kHz stimulation is emphasized – dashed line at 1 kHz in B, aqua curve in C. x-axis plotted as distance from apex. (D) Amplitude and phase of the response to 1 kHz stimulation, with x-axis reversed to distance toward apex. (E) Traveling wave patterns derived from D.

Fig. 5

Basilar membrane displacement measured by Rhode in chinchilla. Upper panels show amplitude and phase as a function of frequency. In the lower two panels the data are replotted as the response pattern, assuming scaling symmetry and using the tonotopic map.

Fig. 6

Pressure close to the BM measured by Olson in gerbil. Upper panels show amplitude and phase as a function of frequency. In the lower two panels the data are replotted as the response pattern, assuming scaling symmetry and using the tonotopic map.

Fig. 7

Results from Ruggero et al. (2000) demonstrated the similarity between BM and AN tuning in the cochlear base.

Fig. 8

Basilar membrane compliance and stiffness as a function of location from stapes. (A) Data from Békésy. (B) Stiffness replotted as Pa/m. Guinea pig and human data derived from panel A. Gerbil results derived from more recent point stiffness measurements. (C) Same as B except x-axis is percent distance from stapes, and additional basal measurements of stiffness included.

Fig. 9

Longitudinal anatomy of the organ of Corti. OHCs, outlined in black, are ∼10 μm in diameter. Gray supporting structures are Deiters cells.

Fig. 10

Responses of a time-domain model to 2 kHz stimulation, with responses normalized to the stimulus level in the bottom panel.