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

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.

Peristimulus Time Responses Predict Adaptation and Spontaneous Firing of Auditory-Nerve Fibers: From Rodents Data to Humans

“…1C). This filter bandwidth was chosen according to the spectrum of the spontaneous neural noise, which is centered ;800-900 Hz in gerbils (Batrel et al, 2017), mice (A. Huet, C. Batrel, J-L. Puel, and J. Bourien, unpublished observations), and humans (Pardo-Jadue et al, 2017;Verschooten et al, 2018). The filter output was then rectified (full-wave rectification) and smoothed (moving average of the elements of the vector with a fixed window length of 1 ms, function smooth in MATLAB) to obtain a rectified smoothed signal (Fig.…”

“…To collect more data, a noninvasive technique is thus needed, especially to record PSTRs in awake subjects. Given that the spontaneous neural noise (900 Hz peak) can be extracted in the human using ear canal recording techniques (Pardo-Jadue et al, 2017), we expect that the signal-to-noise ratio is sufficient to extract PSTR using a tympanic electrode. If not, we can alternatively use a transtympanic electrode (Verschooten et al, 2018).…”

Probing adaptation and spontaneous firing in human auditory-nerve fibers with far-field peri-stimulus time responses

“…To collect more data, a non-invasive technique is thus need, especially to record PSTRs in awake subjects. Given that the spontaneous neural noise (900 Hz peak) can be extracted in the human using ear canal ECochG recording techniques (Pardo-Jadue et al, 2017), we expect that the signal-to-noise ratio is sufficient to extract neurophonic responses using a tympanic electrode. If not, we can alternatively use the classical transtympanic ECochG.…”

Respuestas cerebrales al silencio: hacia una nueva forma de evaluación clínica de la audición

“…Sabemos que en el nervio auditivo las fibras nerviosas presentan una tasa de descarga basal en ausencia de estimulación auditiva 20 . Si bien, no se han descrito potenciales evocados por silencio a nivel coclear, se puede medir el ruido eléctrico de la ventana redonda o del tímpano en condiciones de silencio 21,22 . Esta señal bioeléctrica fue descrita en 1990 por Dolan y cols.…”

“…Este tipo de potencial aún no se utiliza en la práctica clínica, pero podría ser de utilidad para evaluar la función del nervio auditivo en pacientes candidatos a implante coclear o con tinnitus. Por otro lado, existe evidencia de que el silencio puede afectar la duración y la morfología de los potenciales evocados auditivos de tronco encefálico, donde se ha reportado que gaps de duración más cortas se asocian a una disminución en la amplitud en las ondas de potenciales evocados de latencia media 21,22 .…”