On the Origin of the 1,000 Hz Peak in the Spectrum of the Human Tympanic Electrical Noise.

Javiera Pardo-Jadue,Constantino D Dragicevic,Macarena Bowen,Paul H Delano

doi:10.3389/fnins.2017.00395

Javiera Pardo-Jadue, Constantino D Dragicevic + Show 2 more

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https://doi.org/10.3389/fnins.2017.00395

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Abstract

The spectral analysis of the spontaneous activity recorded with an electrode positioned near the round window of the guinea pig cochlea shows a broad energy peak between 800 and 1,000 Hz. This spontaneous electric activity is called round window noise or ensemble background activity. In guinea pigs, the proposed origin of this peak is the random sum of the extracellular field potentials generated by action potentials of auditory nerve neurons. In this study, we used a non-invasive method to record the tympanic electric noise (TEN) in humans by means of a tympanic wick electrode. We recorded a total of 24 volunteers, under silent conditions or in response to stimuli of different modalities, including auditory, vestibular, and motor activity. Our results show a reliable peak of spontaneous activity at ~1,000 Hz in all studied subjects. In addition, we found stimulus-driven responses with broad-band noise that in most subjects produced an increase in the magnitude of the energy band around 1,000 Hz (between 650 and 1,200 Hz). Our results with the vestibular stimulation were not conclusive, as we found responses with all caloric stimuli, including 37°C. No responses were observed with motor tasks, like eye movements or blinking. We demonstrate the feasibility of recording neural activity from the electric noise of the tympanic membrane with a non-invasive method. From our results, we suggest that the 1,000 Hz component of the TEN has a mixed origin including peripheral and central auditory pathways. This research opens up the possibility of future clinical non-invasive techniques for the functional study of auditory and vestibular nerves in humans.

Highlights

Auditory nerve fibers (ANF) transmit action potentials from the cochlea to the brain
1,000 Hz Peak in Tympanic Electric Noise potentials of the auditory nerve last 1–2 ms (Kiang et al, 1976), their spectral analysis contributes to the frequency band of this peak
While stimulus driven auditorynerve activity can be measured through compound action potentials of the auditory nerve (CAP) or by means of wave I from auditory brainstem responses, the spontaneous activity of ANF can only be recorded during neurosurgical procedures, like cerebellopontine angle surgery (Martin, 1995)

Summary

Introduction

Auditory nerve fibers (ANF) transmit action potentials from the cochlea to the brain This neural activity can be recorded spontaneously, -in the absence of acoustic stimulation-, or in response to auditory stimuli (Walsh et al, 1972; Kiang et al, 1976; Manley and Robertson, 1976; Liberman and Kiang, 1978). 1,000 Hz Peak in Tympanic Electric Noise potentials of the auditory nerve last 1–2 ms (Kiang et al, 1976), their spectral analysis contributes to the frequency band of this peak. These authors suggested that this peak at ∼900 Hz reflects the sum of the spontaneous discharge of auditory nerve neurons (Dolan et al, 1990). To date there are no good non-invasive electrophysiological measures of auditory nerve status in profound deaf patients that are candidates for cochlear implantation

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