Distortion-product otoacoustic emission suppression tuning curves in hearing-impaired humans

Abstract

Distortion-product otoacoustic emission (DPOAE) suppression tuning curves (STCs) were measured in 65 hearing-impaired (HI) subjects at f 2 frequencies of 2.0, 2.8, 4.0, and 5.6 kHz and L 2 levels relative to sensation level (SL) from 10 dB to as much as 50 dB. Best frequency, cochlearamplifier gain (tip-to-tail difference, T-T), and tuning (Q ERB ) were estimated from STCs. As with normal-hearing (NH) subjects, T-T differences and Q ERB decreased as L 2 increased. T-T differences and Q ERB were reduced in HI ears (compared to normal) for conditions in which L 2 was fixed relative to behavioral threshold (dB SL). When STCs were compared with L 2 at constant sound pressure levels (dB SPL), differences between NH and HI subjects were reduced. The large effect of level and small effect of hearing loss were both confirmed by statistical analyses. Therefore, the magnitude of the differences in DPOAE STCs between NH and HI subjects is mainly dependent on the manner in which level (L 2 ) is specified. Although this conclusion may appear to be at odds with previous, invasive measures of cochlear-response gain and tuning, the apparent inconsistency may be resolved when the manner of specifying stimulus level is taken into account.

Tone-burst auditory brainstem response wave V latencies in normal-hearing and hearing-impaired ears

“…When compared at equivalent SLs, the latencies from the HL group that were prolonged at equivalent SPLs approximated latencies for the NH group. In contrast, the latencies from the HL group that approximated NH latencies at equivalent SPLs were shorter than those in NH ears, an observation that is consistent with the level effects observed in DPOAE STCs (Gruhlke et al, 2012).…”

“…By applying this relationship to wave V latencies in NH ears and ears with mild-to-moderate HL (assuming identical synaptic and neural delays), the similarity in latencies at equivalent SPLs implies similar cochlear tuning. This hypothesis is consistent with the observed similarity of DPOAE STCs in HL and NH ears when level is equated in dB SPL (Gruhlke et al, 2012). The interpretation of the previous DPOAE STC data and the present latency data may appear to be at odds with work suggestive of broader auditory filters in ears with cochlear damage.…”

“…This study was motivated by recent work demonstrating that the effect of HL on DPOAE STCs is small compared to the effect of stimulus level (Abdala and Fitzgerald 2003;Gorga et al, 2003;Gruhlke et al, 2012). ABR latencies provide another means to evaluate the interactions between HL and stimulus level and it was hypothesized that comparisons between latencies in ears with NH and ears with HL would be consistent with the level effects observed in the DPOAE STC data.…”

“…Recent work has demonstrated that differences in distortion-product otoacoustic emission (DPOAE) suppression tuning curves (STCs) between ears with normal hearing (NH) and ears with hearing loss (HL) depend on the stimulus level at which comparisons are made (Abdala and Fitzgerald, 2003;Gorga et al, 2003;Gruhlke et al, 2012). When compared at equal stimulus-probe levels (primary levels for f 1 and f 2 , the stimulus frequencies eliciting the DPOAE) relative to threshold (i.e., sensation level, SL), STCs in ears with mild-to-moderate HL were characterized by reduced gain (as estimated by tip-to-tail differences) and broader tuning (based on the quality factor, Q), compared to ears with NH.…”

Stimulus-Frequency Otoacoustic Emission Suppression Tuning in Humans: Comparison to Behavioral Tuning

“…It is also not clear how well SFOAE STCs would reflect changes in frequency selectivity due to hearing loss. Effects of cochlear insults on OAE suppression have been studied using DPOAEs and SOAEs but results have been inconclusive (Ruggero et al 1983;Clark et al 1984;Ruggero et al 1984;Powers et al 1995;Martin et al 1998;Sun et al 2000;Howard et al 2002;Abdala and Fitzgerald 2003;Gorga et al 2003;Howard et al 2003;Gruhlke et al 2012). Although SFOAE can be measured in hearing-impaired subjects (Ellison and Keefe 2005), it is not clear whether SFOAE STCs may provide a better measure of frequency selectivity in cases of cochlear insults.…”