Within- and Across-Subject Variability of Repeated Measurements of Medial Olivocochlear-Induced Changes in Transient-Evoked Otoacoustic Emissions

Abstract

Results indicated that a wide range of within- and across-subject variability of MOC shifts was present in a group of young normal-hearing individuals. In some cases, very large changes in MOC shifts (e.g., 1.5 to 2 dB) would need to occur before one could attribute the change to either an intervention or pathology, rather than to measurement variability. It appears that MOC shifts, as analyzed in the present study, may be too variable for clinical use, at least in some individuals. Further study is needed to determine the extent to which changes in MOC shifts can be reliably measured across time for clinical purposes.

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).…”

Concurrent measures of contralateral suppression of transient-evoked otoacoustic emissions and of auditory steady-state responses

“…The CAS was presented at an overall root-mean-square (RMS) level of 60 dB(A) sound pressure level (SPL). This level was selected based on previous work demonstrating that it is an effective activator of the MOC (e.g., Guinan et al, 2003;Mertes and Goodman, 2016) while minimizing elicitation of the middle-ear muscle reflex (MEMR), which can confound the interpretation of changes in both OAE levels and stimulus levels (Goodman et al, 2013) as discussed below. The SPL of the CAS was calibrated in an AEC202 2cc coupler (Larson Davis, Depew, NY).…”

“…To ensure that subjects had a consistent attentional state during the recordings, subjects participated in a visualattention task described by Mertes and Goodman (2016). Specifically, subjects watched a computer screen inside the sound booth and were instructed to quietly click a mouse button as soon as possible when the computer screen turned blue, which happened every 1-4 s, selected from a random uniform distribution.…”

“…It was hypothesized that both response measures would demonstrate high test-retest reliability within a session, based on previous studies of MOC test-retest reliability (Mishra and Lutman, 2013;Mertes and Goodman, 2016). It was further postulated that contralateral suppression of ASSRs would be significantly larger than contralateral suppression of TEOAEs, as was demonstrated for contralateral suppression of auditory nerve responses (Puria et al, 1996;Chabert et al, 2002;Lichtenhan et al, 2016).…”

“…Contralateral suppression of OAEs is typically used to assess MOC activity, wherein OAEs are measured without and with contralateral acoustic stimulation (CAS) that activates the contralateral MOC pathway. Contralateral suppression has been described for all types of OAEs, including spontaneous otoacoustic emissions (SOAEs) (e.g., Mott et al, 1989;Zhao and Dhar, 2010), stimulus frequency otoacoustic emissions (SFOAEs) (e.g., Guinan et al, 2003;Lilaonitkul and Guinan, 2009;Zhao et al, 2015), distortion-product otoacoustic emissions (DPOAEs) (e.g., Siegel and Kim, 1982;Moulin et al, 1993;Abdala et al, 2009;Deeter et al, 2009), and transient-evoked otoacoustic emissions (TEOAEs) (e.g., Collet et al, 1990;Hood et al, 1996;Mertes and Goodman, 2016). Unlike DPOAEs, which are generated in the cochlea by two mechanisms, TEOAEs elicited by low to moderate stimulus levels are generated by only one cochlear mechanism (Shera and Guinan, 1999), which simplifies the interpretation of the TEOAE magnitude changes observed in the presence of CAS.…”