Measurement of basilar membrane motion in the guinea pig using the Mössbauer technique

Abstract

Basilar membrane motion was measured at the 16-19 kHz place of the guinea pig cochlea using the Mössbauer technique. The threshold of the gross cochlear action potential (CAP) evoked by pure-tone bursts was used as an indication of neural threshold. CAP threshold deteriorated progressively after the cochlea was opened and the Mössbauer source placed on the basilar membrane. A close relationship was found between the amplitude of basilar membrane motion at the source place frequency and CAP threshold. Basilar membrane velocity at CAP threshold SPL was about 0.04 mm/s over a 60-dB range of CAP threshold. Intensity functions for basilar membrane motion were linear for frequencies more than an octave below the source place frequency but demonstrated progressive saturation for frequencies greater than an octave below the CF. This nonlinear behavior was eliminated as the CAP threshold became less sensitive and was absent post mortem. Isovelocity curves at the 0.04 mm/s criterion were remarkably similar to frequency threshold curves from primary afferent fibers innervating a similar place on the basilar membrane. The isovelocity curve was a better fit than the isoamplitude curve suggesting that inner hair cells respond to basilar membrane velocity. As the CAP threshold deteriorated, the isovelocit curves lost sensitivity around the best frequency, whereas sensitivity to frequencies below 10 kHz remained constant even after the animal was killed. We suggested that most of the frequency response and nonlinear behavior of inner hair cells and afferent fibers may be found in basilar motion.

Frequency selectivity of phase-locking of complex sounds in the auditory nerve of the rat

“…This hypothesis, that resonance between the tectorial membrane stereocilia is coupled to basilar membrane motion, was later adopted by Allen [l]. Assuming a strong coupling between the organ of Corti and the tectorial membrane, Zwislocki [50] has been able to show in transmission line models of the basilar membrane a degree of tuning as sharp as that shown in experiments on motion of the basilar membrane [40], and in studies of the frequency threshold curves of single auditory nerve fibers (see, e.g. [20]).…”

“…It has recently been shown that the vibration amplitude of the basilar membrane in the uninjured cochlea at low sound intensities is as sharply tuned as are the frequency threshold curves of the auditory nerve fibers [19,39,40]. It is therefore most likely that the changes seen in the frequency selectivity of auditory nerve fibers as a function of sound intensity are due to the tuning of the basilar membrane.…”

Computational Modeling of Individual Differences in Behavioral Estimates of Cochlear Nonlinearities

“…For subjects in the mid and high threshold groups, poor detection efficiency does not necessarily indicate a deficit of the central auditory system but may suggest a peripheral degradation of important cues that cannot be resolved by the central detector. The degree to which detection efficiency is compromised by peripheral degradation of detection cues is unknown, as are the sources of this degradation; however, these sources may be related to poorer frequency resolution (e.g., Sellick et al 1982) or altered neural adaptation (Scheidt et al 2010). Peripheral degradation of detection cues may also contribute to increased individual differences among hearing-impaired listeners, as compared to normal-hearing listeners, in TMCs and other psychophysical and speech perception tasks (e.g., Moore 2007).…”

The Role of Temporal Fine Structure Processing in Pitch Perception, Masking, and Speech Perception for Normal-Hearing and Hearing-Impaired People

“…For example, the TFS at a 1-kHz rate may be decoded best by the central neurons that are tuned (in a normal ear) close to 1 kHz. Hearing loss may produce a shift in frequency-place mapping (Liberman and Dodds 1984;Sellick et al 1982) and disrupt the decoding process. Note that this explanation depends on the assumption that the central decoding mechanism is, to some extent, "hard wired" 5.…”