Influence of the stimulus presentation rate on medial olivocochlear system assays

Abstract

Click evoked otoacoustic emissions (CEOAEs) are commonly used both in research and clinics to assay the medial olivocochlear system (MOC). Clicks presented at rates >50 Hz in the contralateral ear have previously been reported to evoke contralateral MOC activity. However, in typical MOC assays, clicks are presented in the ipsilateral ear in conjunction with MOC elicitor (noise) in the contralateral ear. The effect of click rates in such an arrangement is currently unknown. A forward masking paradigm was used to emulate typical MOC assays to elucidate the influence of ipsilateral click presentation rates on MOC inhibition of CEOAEs in 28 normal hearing adults. Influence of five click rates (20.83, 25, 31.25, 41.67, and 62.5 Hz) presented at 55 dB peSPL was tested. Results indicate that click rates as low as 31.25 Hz significantly enhance contralateral MOC inhibition, possibly through the activation of ipsilateral and binaural MOC neurons with potential contributions from the middle ear muscle reflex. Therefore, click rates ≤25 Hz are recommended for use in MOC assays, at least for 55 dB peSPL click level.

Click evoked middle ear muscle reflex: Spectral and temporal aspectsa)

“…Therefore, for OAE-based assays of the MOCR, it is critical that the presence of the MEMR is not based on MEMR thresholds obtained from clinical tympanometers. We emphasize that monitoring the OAE-evoking stimulus is currently the optimal solution to sensitive monitoring of MEMR activation, in keeping with previous recommendations (Guinan, 2010;Zhao and Dhar, 2012;Mertes and Goodman, 2015;Boothalingam and Purcell, 2015).…”

“…As such, when frequency-specific changes are not considered (e.g., Boothalingam and Purcell, 2015;Mertes, 2020), MEMR detection may be less sensitive. This is because MEMR-induced stimulus changes at the lower and higher frequencies may partially cancel out and falsely reflect little or no change.…”

Contralateral Inhibition of Click- and Chirp-Evoked Human Compound Action Potentials

“…Stimulus presentation rate was Gaussian distributed from 9.1/s to 13.1/s with a mean rate of 11.1/s. This relatively slow range of presentation rates was selected to ensure that the stimuli did not temporally summate to activate the MOC reflex, which has been shown to affect OAE measurements at stimulus presentation rates as low as 30/s–50/s (Veuillet et al, 1991; Francis and Guinan, 2010; Boothalingam and Purcell, 2015). A Gaussian-distributed (i.e., “temporally jittered”) presentation rate was selected to facilitate subject alertness, as this may influence MOC reflex strength (Aedo et al, 2015).…”

Human medial efferent activity elicited by dynamic versus static contralateral noises

“…However, Boothalingam et al (2014) found a trend of reduced contralateral inhibition of otoacoustic emissions (OAEs) elicited with single-tone stimuli (stimulus frequency OAEs) when the tones were AM versus unmodulated. No significant differences were seen in contralateral inhibition when elicited by a babble noise relative to white noise (Timpe-Syverson and Decker, 1999;Papsin et al, 2014), but these studies did not report sufficient controls for middle-ear muscle reflex activation which could interfere with the interpretation of results (Goodman et al, 2013) and the click stimulus rate of 50/s may have elicited the ipsilateral MOCR (Boothalingam and Purcell, 2015). A recent paper examined the effect of a variety of contralateral noises on contralateral inhibition (Kalaiah et al, 2017).…”