Stability of the Medial Olivocochlear Reflex as Measured by Distortion Product Otoacoustic Emissions

Abstract

Purpose: The purpose of this study was to assess the repeatability of a fine-resolution, distortion product otoacoustic emission (DPOAE)-based assay of the medial olivocochlear (MOC) reflex in normal-hearing adults. Method: Data were collected during 36 test sessions from 4 normal-hearing adults to assess short-term stability and 5 normal-hearing adults to assess long-term stability. DPOAE level and phase measurements were recorded with and without contralateral acoustic stimulation. MOC reflex indices were computed by (a) noting contralateral acoustic stimulation-induced changes in DPOAE level (both absolute and normalized) at fine-structure peaks, (b) recording the effect as a vector difference, and (c) separating DPOAE components and considering a component-specific metric.Results: Analyses indicated good repeatability of all indices of the MOC reflex in most frequency ranges. Short-and long-term repeatability were generally comparable. Indices normalized to a subject's own baseline fared best, showing strong short-and long-term stability across all frequency intervals. Conclusions: These results suggest that fine-resolution DPOAE-based measures of the MOC reflex measured at strategic frequencies are stable, and natural variance from day-to-day or week-to-week durations is small enough to detect between-group differences and possibly to monitor intervention-related success. However, this is an empirical question that must be directly tested to confirm its utility.

Short Term Test-Retest Reliability of Contralateral Inhibition of Distortion Product Otoacoustic Emissions

“…Many of the researchers have measured MOCB activity using contralateral inhibition of click evoked or transient evoked otoacoustic emissions (TEOAEs) [ 6 - 8 , 10 ] and contralateral acoustic stimulation (CAS) has shown to reduce the amplitude of transient evoked otoacoustic emissions for various types of noise [ 11 ]. The effects of CAS on the DPOAE has been reported by several investigators [ 5 , 12 - 15 ] and findings of these investigations have reported both reduction and enhancement of amplitude of DPOAEs [ 12 , 13 , 16 , 17 ].…”

“…When the DPOAEs are measured in ear canal, the constructive and destructive interferences between the two components of DPOAE results in peaks and dips in the response amplitude as a function of frequency. This oscillation in DPOAE phase and level is referred to as DPOAE fine structure [ 5 ].…”

“…These investigators reported good short-term reliability (α≥0.8) of contralateral inhibition of TEOAEs between 1 and 4 days for most of the test conditions. Similarly, the short-term stability of MOC reflex using DPOAEs has been investigated by few investigators [ 5 , 15 , 21 ]. Wagner, et al [ 21 ] repeated the measurement of contralateral inhibition of DPOAEs using custom made research equipment on average of 5.5 days.…”

Time–frequency decomposition of click evoked otoacoustic emissions in children

“…Since reflection source emissions are generated near the peak of the traveling wave, OAEs recorded at low levels are sensitive to subtle cochlear amplifier gain changes (Shera, 2004). For example, medial efferent activation by contralateral acoustic stimulation produces larger changes in the reflection-compared to the distortion-component of distortion product OAEs (Abdala et al, 2009;Mishra and Abdala, 2015). Additionally, reflection-source OAE delays, including CEOAE latencies, can be applied to objectively estimate cochlear tuning in humans and other animals (Bentsen et al, 2011;Bergevin et al, 2012;Joris et al, 2011;Keefe, 2012;Moleti et al, 2008;Shera et al, 2002;Sisto and Moleti, 2007).…”

“…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).…”