D Amani-Taleshi | PubMed Health

PubMed2000

Mathematical decomposition of the round window potential.

We present an algorithm called the median transform which can be used to decompose the round window auditory potential into AC and DC components. The first of these is identified with the cochlear microphonic, and the second with the combined summating and compound action potentials. Elsewhere in this volume, the algorithm is employed as an intermediate step in obtaining the instantaneous frequency of the CM. Since the algorithm is easily implemented and operates entirely in the time domain, it may prove useful to clinicians as well as researchers.

Action Potentials↗

PubMed2000

Characterizing non-linearity in the cochlear microphonic using the instantaneous frequency.

In this paper, we examine the non-linearity of mechano-electric transduction in the cochlea by computing the instantaneous frequency (IF) of the cochlear microphonic (CM) in response to sinusoidal stimuli. In contrast to a linear system which yields a constant IF when driven with a sinusoid, the IF of the CM varied during one period of oscillation. This variation was not symmetric, but differed for positive and negative slopes of the CM. Administration of tetrodotoxin to eliminate neural activity indicated that the variation of the IF was not due to neural contamination. Moreover, comparing the IF of the stimulus to that of the CM indicated that the IF was not due to non-linearity in the acoustic signal. Signal frequency, signal level and acoustic trauma altered the IF. A cochlear model of the CM was developed to determine the influence of the saturation of hair-cell receptor currents and vector summation on the IF. Results indicated that these factors could not fully account for the variation in the IF. We conclude that the variation in IF within one period of cochlear partition vibration indicates that the mechanical and/or electrical oscillations which produce the CM differ from those of a linear system.

Acoustic Stimulation↗