Transient-evoked otoacoustic emissions and high-frequency acoustic trauma in the guinea pig

Abstract

Transient-evoked otoacoustic emissions (TEOE) disappear when hearing loss exceeds 40 dB in the range 1-4 kHz, due to impairment of cochlear outer hair cells. Early screening of sensorineural hearing losses is based on this finding. However, little is known as to the frequency specificity of TEOE abnormalities in a damaged cochlea. TEOE were recorded in 18 normally hearing guinea pigs in a range from 1.5 to 5 kHz before and after exposure to loud pure tones (3-10 kHz, 95-105 dB SPL, 1-10 min). The thresholds of eighth-nerve compound action potentials (CAP) were monitored with a round-window electrode; it was confirmed that acoustic overexposure resulted in typical high-frequency threshold elevations (10 to 50 dB). Most TEOE components were found at lower frequencies at which CAP thresholds did not change. However, a significant linear regression was found between their amplitudes and the percentage of basal cochlea with unaltered CAP thresholds (r = 0.69, p < 0.0001). Two alternative hypotheses are proposed to account for this correlation. Either acoustic trauma induced some minute cochlear damage at places tuned to low frequencies and TEOE were more sensitive to it than CAP thresholds, or significant contributions to lower-frequency TEOE came from the most damaged cochlear places tuned to much higher frequencies.

Simultaneous suppression of tone burst-evoked otoacoustic emissions – Effect of level and presentation paradigm

“…This in turn may strengthen the notion that TEOAE component responses are substantially locally generated, rather than generated over a wide region of the basilar membrane, as has been argued by Sutton (1985); Avan et al (1995); Avan et al (1997) and Withnell and Yates (1998) and Carvalho et al (2003).…”

“…Xu et al (1994) appear to leave open the possibility that basal areas of the cochlea, well remote from the region of excitation due to a particular tone burst, may have been involved in the suppression observed in their data. The involvement of remote basal regions of the cochlea in TEOAE generation has been suggested by other authors (Sutton, 1985;Avan et al, 1995;Avan et al, 1997;Withnell and Yates, 1998).…”

“…Withnell and Yates (1998) also observed enhancement of TEOAE responses at frequencies lower than the "suppressor" tone frequency. Avan et al (1995Avan et al ( , 1997 observed changes in low frequency components of the TEOAE following damage to the basal region of the BM. Carvalho et al (2003) reported TEOAE phase data that suggested that a TEOAE "at frequency f cannot come from that place tuned to f".…”

Estimating Cochlear Frequency Selectivity with Stimulus-frequency Otoacoustic Emissions in Chinchillas

“…Suppression patterns, noise-exposure experiments, component decomposition analysis and correlations between OAEs and hearing threshold suggest that SFOAEs, transient-evoked (TE) OAEs, and distortion-product (DP) OAEs in humans and several laboratory species may have an extended generation region (e.g. Sutton 1985;Guinan 1990;Avan et al 1993Avan et al , 1995Avan et al , 1997Withnell et al 2000;Harding et al 2002;Ellison and Keefe 2005;Dreisbach et al 2008;Martin et al 2009Martin et al , 2010Charaziak et al 2013;Sisto et al 2013). …”

Tuning of SFOAEs Evoked by Low-Frequency Tones Is Not Compatible with Localized Emission Generation

“…If the OAE generation process is linked to OHC function at a given cochlear location, introducing localized damage/interruption of OHC function via acoustic overstimulation should reveal the spatial extent of OAE sources. This method has been used for investigating contributions from spatially distributed OAE sources in the case of transient-evoked (TE) OAEs (Avan et al 1995;Withnell et al 2000) as well as distortion-product (DP) OAEs (Martin et al 2010).…”