Otoacoustic-emission-based medial-olivocochlear reflex assays for humans

Abstract

Otoacoustic emission (OAE) tests of the medial-olivocochlear reflex (MOCR) in humans were assessed for viability as clinical assays. Two reflection-source OAEs [TEOAEs: transient-evoked otoacoustic emissions evoked by a 47 dB sound pressure level (SPL) chirp; and discrete-tone SFOAEs: stimulus-frequency otoacoustic emissions evoked by 40 dB SPL tones, and assessed with a 60 dB SPL suppressor] were compared in 27 normal-hearing adults. The MOCR elicitor was a 60 dB SPL contralateral broadband noise. An estimate of MOCR strength, MOCR%, was defined as the vector difference between OAEs measured with and without the elicitor, normalized by OAE magnitude (without elicitor). An MOCR was reliably detected in most ears. Within subjects, MOCR strength was correlated across frequency bands and across OAE type. The ratio of across-subject variability to within-subject variability ranged from 2 to 15, with wideband TEOAEs and averaged SFOAEs giving the highest ratios. MOCR strength in individual ears was reliably classified into low, normal, and high groups. SFOAEs using 1.5 to 2 kHz tones and TEOAEs in the 0.5 to 2.5 kHz band gave the best statistical results. TEOAEs had more clinical advantages. Both assays could be made faster for clinical applications, such as screening for individual susceptibility to acoustic trauma in a hearing-conservation program. [http://dx

Influence of the stimulus presentation rate on medial olivocochlear system assays

“…Therefore, the change in CEOAE level due to the presence of IAS and CE-block could arise from transient OAEs and potential SSOAEs caused by IAS and CEblock clicks. SSOAEs were not measured in the current study, however, Marshall et al 35 reported that presence of SSOAEs in their chirp-evoked OAE sample did not affect the observed of MOC inhibition between participants withand without-SSOAEs. Also, considering that the amount of MOC inhibition caused by both IAS and CAS is statistically the same and numerically very similar, it is unlikely that the SSOAEs and transient OAEs evoked by IAS/CE-block clicks, if present, had a large effect on the observed MOC inhibition in the current study.…”

“…However, a recent study tested the influence of SSOAEs on MOC inhibition of CEOAEs, and found no difference in the strength of MOC inhibition between individuals with SSOAEs and individuals with no SSOAEs. 35 This report suggests that the presence of SSOAE in the CEOAE spectrum may not significantly influence the observed MOC inhibition. Most studies that investigate the MOC using clicks have used a 50 Hz click presentation rate as a safe cut-off to avoid evoking ipsilateral MOC activity.…”

Time–frequency decomposition of click evoked otoacoustic emissions in children

“…Each participant was tested for the presence of spontaneous OAEs (SOAEs) using the synchronized SOAE technique (reported in Marshall et al, 2014). Briefly, responses to 1000 clicks at 55 dB peSPL, presented every 64 ms, were recorded in a linear mode.…”

“…For instance, CEOAE latency can be used to objectively estimate cochlear tuning in the pediatric population, in whom psychophysical tuning curves may be difficult to obtain (Moleti and Sisto, 2003;Moleti et al, 2008). The latency can be applied to accurately characterize the efferent effects on cochlear mechanisms (Francis and Guinan, 2010) and compute a vector metric to index efferent reflex (Abdala et al, 2013;Marshall et al, 2014;Mishra and Abdala, 2015).…”

Efferent modulation of pre-neural and neural distortion products

“…OAE-based measurements have revealed characteristics of MOC reflex tuning (e.g., Veuillet et al 1991; Chéry-Croze et al 1993; Lilaonitkul and Guinan 2007; Zhao & Dhar, 2012), strength (e.g., Backus & Guinan, 2007; Marshall et al, 2014), and the mechanism’s possible involvement in directed auditory attention (e.g., Froehlich et al, 1993; de Boer & Thornton, 2007; Garinis et al, 2011) or listening in noise tasks (e.g., Giraud et al, 1997; Kumar & Vanaja, 2004; de Boer & Thornton, 2008; Smith & Cone, 2015; de Boer et al, 2012). However, a major limitation of this approach is that OAEs are insensitive to MOC reflex effects on the neural ensembles that mediate human hearing, and the functional consequences of this mechanism remain unclear.…”