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

Abstract

It has been suggested that the tuning of the cochlear filters can be derived from measures of otoacoustic emissions (OAEs). Two approaches have been proposed to estimate cochlear frequency selectivity using OAEs evoked with a single tone (stimulus-frequency (SF)) OAEs: based on SFOAE group delays (SF-GDs) and on SFOAE suppression tuning curves (SF-STCs). The aim of this study was to evaluate whether either SF-GDs or SF-STCs obtained with low probe levels (30 dB SPL) correlate with more direct measures of cochlear tuning (compound action potential suppression tuning curves (CAP-STCs)) in chinchillas. The SFOAE-based estimates of tuning covaried with CAPSTCs tuning for 93 kHz probe frequencies, indicating that these measures are related to cochlear frequency selectivity. However, the relationship may be too weak to predict tuning with either SFOAE method in an individual. The SF-GD prediction of tuning was sharper than CAP-STC tuning. On the other hand, SF-STCs were consistently broader than CAP-STCs implying that SFOAEs may have less restricted region of generation in the cochlea than CAPs. Inclusion of G3 kHz data in a statistical model resulted in no significant or borderline significant covariation among the three methods: neither SFOAE test appears to reliably estimate an individual's CAP-STC tuning at low-frequencies. At the group level, SF-GDs and CAP-STCs showed similar tuning at low frequencies, while SF-STCs were over five times broader than the CAP-STCs indicating that low-frequency SFOAE may originate over a very broad region of the cochlea extending ≥5 mm basal to the tonotopic place of the probe.

Traveling Waves on the Organ of Corti of the Chinchilla Cochlea: Spatial Trajectories of Inner Hair Cell Depolarization Inferred from Responses of Auditory-Nerve Fibers

“…Interestingly, stimulus-frequency otoacoustic emissions in chinchillas exhibit frequency dependencies consistent with the existence of basal and apical segments of the cochlea which transition in the 6.5–9 mm region. Their average magnitudes exhibit a conspicuous minimum around 3 kHz (Siegel et al, 2005), whose characteristic place lies in the transition region, and their suppression tuning curves differ drastically for probe frequencies 4 and 12 kHz, which closely resemble ANF tuning curves, vs. 1-kHz probes, which have high-frequency arms that are nearly flat over a 2-octave range, as might be expected from basal emission sources due to reflections at the transition region (Charaziak and Siegel, 2012). …”

Using Cochlear Microphonic Potentials to Localize Peripheral Hearing Loss

“…Most of our methods have been described previously (Charaziak and Siegel, 2014, 2015). Adult chinchillas were anesthetized with ketamine hydrochloride (20 mg/kg, injected subcutaneously), followed by Dial (diallylbarbituric acid) in urethane (initial doses 50 and 200 mg/kg, respectively) with additional doses (20% of the initial one) given as necessary.…”

The influence of probe level on the tuning of stimulus frequency otoacoustic emissions and behavioral test in human

“…In 1980, Kemp et al found that fully suppressed SFOAE suppression tuning curve (STC) matched closely the tone-on-tone total masking PTC, and firstly predicted that SFOAE STCs might be used to evaluate cochlear function objectively [ 19 ]. Since their pioneering work, despite the complexity of SFOAE extraction [ 20 – 22 ] and uncertainty about the mechanism of SFOAE generation [ 23 – 25 ], SFOAE STCs are regarded as reflecting the auditory tuning in some laboratory species [ 26 , 27 ] and behavioural tuning in humans [ 28 – 30 ]. Additionally, the effect of probe level on the tuning of SFOAE STCs and other types of measurement for FS based on SFOAEs (e.g., SFOAE group delays) were observed in many investigations [ 27 – 29 , 31 ].…”

“…Since their pioneering work, despite the complexity of SFOAE extraction [ 20 – 22 ] and uncertainty about the mechanism of SFOAE generation [ 23 – 25 ], SFOAE STCs are regarded as reflecting the auditory tuning in some laboratory species [ 26 , 27 ] and behavioural tuning in humans [ 28 – 30 ]. Additionally, the effect of probe level on the tuning of SFOAE STCs and other types of measurement for FS based on SFOAEs (e.g., SFOAE group delays) were observed in many investigations [ 27 – 29 , 31 ]. Keefe et al measured SFOAE STCs in humans at probe levels of 20–60 dB SPL and reported that the quality factor based on the equivalent rectangular bandwidth ( Q ERB , indicating the tuning sharpness) of SFOAE STCs varied little with probe level changing [ 28 ].…”

“…For laboratory species, Cheatham et al reported that SFOAE STCs in wild-type mice might get broader at moderate probe levels [ 26 ]. The decreasing in sharpness of SFOAE STCs tuning with increasing probe level was also observed in chinchillas, but the Q 10 derived from SFOAEs group delay in chinchillas revealed no significant dependence on probe levels [ 27 ]. In summary, the effect of increasing probe level on the tuning of SFOAE STCs or other FS measurements based on SFOAEs appears controversial.…”