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Outer Hair Cell and Auditory Nerve Function in Speech Recognition in Quiet and in Background Noise

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ABSTRACT

The goal of this study was to describe the contribution of outer hair cells (OHCs) and the auditory nerve (AN) to speech understanding in quiet and in the presence of background noise. Fifty-three human subjects with hearing ranging from normal to moderate sensorineural hearing loss were assayed for both speech in quiet (Word Recognition) and speech in noise (QuickSIN test) performance. Their scores were correlated with OHC function as assessed via distortion product otoacoustic emissions, and AN function as measured by amplitude, latency, and threshold of the VIIIth cranial nerve Compound Action Potential (CAP) recorded during electrocochleography (ECochG). Speech and ECochG stimuli were presented at equivalent sensation levels in order to control for the degree of hearing sensitivity across patients. The results indicated that (1) OHC dysfunction was evident in the lower range of normal audiometric thresholds, which demonstrates that OHC damage can produce “Hidden Hearing Loss,” (2) AN dysfunction was evident beginning at mild levels of hearing loss, (3) when controlled for normal OHC function, persons exhibiting either high or low ECochG amplitudes exhibited no statistically significant differences in neither speech in quiet nor speech in noise performance, (4) speech in noise performance was correlated with OHC function, (5) hearing impaired subjects with OHC dysfunction exhibited better speech in quiet performance at or near threshold when stimuli were presented at equivalent sensation levels. These results show that OHC dysfunction contributes to hidden hearing loss, OHC function is required for optimum speech in noise performance, and those persons with sensorineural hearing loss exhibit better word discrimination in quiet at or near their audiometric thresholds than normal listeners.

No MeSH data available.


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Increasing SNHL is correlated with decreased speech in noise performance. (A) Mean pure tone audiograms from each group. The table lists the p-values between each group by stimulus frequency. Bold text indicates a p < 0.05. (B) Distribution of the subject age (years) in each group. Top graph plots mean values +/1 s.e.m. Bottom graph plots this same data using upper and lower quartiles (box), median values (line within box), maximum and minimum scores (error bars). (C) Speech in noise performance from each group where lower SNR Loss corresponds to better performance in the presence of background noise. Top graph plots mean values ± 1 s.e.m. Bottom graph plots this same data using box and whisker plots. Norm, Normal Hearing Group; Min, Minimal SNHL; Mild, Mild SNHL; Mod, Moderate SNHL; *** statistically significant difference between Normal and Mild SNHL groups; ****statistically significant difference between Normal and Moderate SNHL groups; ++++statistically significant difference between Minimal SNHL and Moderate SNHL groups.
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Figure 3: Increasing SNHL is correlated with decreased speech in noise performance. (A) Mean pure tone audiograms from each group. The table lists the p-values between each group by stimulus frequency. Bold text indicates a p < 0.05. (B) Distribution of the subject age (years) in each group. Top graph plots mean values +/1 s.e.m. Bottom graph plots this same data using upper and lower quartiles (box), median values (line within box), maximum and minimum scores (error bars). (C) Speech in noise performance from each group where lower SNR Loss corresponds to better performance in the presence of background noise. Top graph plots mean values ± 1 s.e.m. Bottom graph plots this same data using box and whisker plots. Norm, Normal Hearing Group; Min, Minimal SNHL; Mild, Mild SNHL; Mod, Moderate SNHL; *** statistically significant difference between Normal and Mild SNHL groups; ****statistically significant difference between Normal and Moderate SNHL groups; ++++statistically significant difference between Minimal SNHL and Moderate SNHL groups.

Mentions: The results show statistically significant correlations between SNHL (measured by hfPTA) and subject age, SIN performance (measured by QSIN SNR Loss), and OHC function (measured by DPAOE amplitude and threshold; Figure 2). In order to visualize these correlations, subjects were ranked by hfPTA and divided into one of four groups based on their degree of high frequency SNHL (Normal Hearing <15 dB HL, n = 7 males and 22 females; Minimal SNHL = 15–24 dB HL, n = 1 male and 3 females; Mild SNHL = 25–39 dB HL, n = 6 males and 4 females; Moderate SNHL = 40–50 dB HL, n = 6 males and 4 females; Figure 3). In clinical audiometry, the Minimal SNHL group represents the lower end of the Normal range and is most often used in pediatric rather than adult audiometry. There was a statistically significant positive correlation between SNHL (hfPTA) and age (τb = 0.636, p = 0.000; Figure 2A). The non-parametric J–T test for ordered alternatives showed that there was a statistically significant trend of increased age with increasing hearing loss (Figure 3B). Specifically, there was a statistically significant increase in age between the Normal hearing (33.7 ± 1.97 years) and Mild (59.6 ± 2.79 years) and Moderate SNHL groups (p = 0.00).


Outer Hair Cell and Auditory Nerve Function in Speech Recognition in Quiet and in Background Noise
Increasing SNHL is correlated with decreased speech in noise performance. (A) Mean pure tone audiograms from each group. The table lists the p-values between each group by stimulus frequency. Bold text indicates a p < 0.05. (B) Distribution of the subject age (years) in each group. Top graph plots mean values +/1 s.e.m. Bottom graph plots this same data using upper and lower quartiles (box), median values (line within box), maximum and minimum scores (error bars). (C) Speech in noise performance from each group where lower SNR Loss corresponds to better performance in the presence of background noise. Top graph plots mean values ± 1 s.e.m. Bottom graph plots this same data using box and whisker plots. Norm, Normal Hearing Group; Min, Minimal SNHL; Mild, Mild SNHL; Mod, Moderate SNHL; *** statistically significant difference between Normal and Mild SNHL groups; ****statistically significant difference between Normal and Moderate SNHL groups; ++++statistically significant difference between Minimal SNHL and Moderate SNHL groups.
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Figure 3: Increasing SNHL is correlated with decreased speech in noise performance. (A) Mean pure tone audiograms from each group. The table lists the p-values between each group by stimulus frequency. Bold text indicates a p < 0.05. (B) Distribution of the subject age (years) in each group. Top graph plots mean values +/1 s.e.m. Bottom graph plots this same data using upper and lower quartiles (box), median values (line within box), maximum and minimum scores (error bars). (C) Speech in noise performance from each group where lower SNR Loss corresponds to better performance in the presence of background noise. Top graph plots mean values ± 1 s.e.m. Bottom graph plots this same data using box and whisker plots. Norm, Normal Hearing Group; Min, Minimal SNHL; Mild, Mild SNHL; Mod, Moderate SNHL; *** statistically significant difference between Normal and Mild SNHL groups; ****statistically significant difference between Normal and Moderate SNHL groups; ++++statistically significant difference between Minimal SNHL and Moderate SNHL groups.
Mentions: The results show statistically significant correlations between SNHL (measured by hfPTA) and subject age, SIN performance (measured by QSIN SNR Loss), and OHC function (measured by DPAOE amplitude and threshold; Figure 2). In order to visualize these correlations, subjects were ranked by hfPTA and divided into one of four groups based on their degree of high frequency SNHL (Normal Hearing <15 dB HL, n = 7 males and 22 females; Minimal SNHL = 15–24 dB HL, n = 1 male and 3 females; Mild SNHL = 25–39 dB HL, n = 6 males and 4 females; Moderate SNHL = 40–50 dB HL, n = 6 males and 4 females; Figure 3). In clinical audiometry, the Minimal SNHL group represents the lower end of the Normal range and is most often used in pediatric rather than adult audiometry. There was a statistically significant positive correlation between SNHL (hfPTA) and age (τb = 0.636, p = 0.000; Figure 2A). The non-parametric J–T test for ordered alternatives showed that there was a statistically significant trend of increased age with increasing hearing loss (Figure 3B). Specifically, there was a statistically significant increase in age between the Normal hearing (33.7 ± 1.97 years) and Mild (59.6 ± 2.79 years) and Moderate SNHL groups (p = 0.00).

View Article: PubMed Central - PubMed

ABSTRACT

The goal of this study was to describe the contribution of outer hair cells (OHCs) and the auditory nerve (AN) to speech understanding in quiet and in the presence of background noise. Fifty-three human subjects with hearing ranging from normal to moderate sensorineural hearing loss were assayed for both speech in quiet (Word Recognition) and speech in noise (QuickSIN test) performance. Their scores were correlated with OHC function as assessed via distortion product otoacoustic emissions, and AN function as measured by amplitude, latency, and threshold of the VIIIth cranial nerve Compound Action Potential (CAP) recorded during electrocochleography (ECochG). Speech and ECochG stimuli were presented at equivalent sensation levels in order to control for the degree of hearing sensitivity across patients. The results indicated that (1) OHC dysfunction was evident in the lower range of normal audiometric thresholds, which demonstrates that OHC damage can produce &ldquo;Hidden Hearing Loss,&rdquo; (2) AN dysfunction was evident beginning at mild levels of hearing loss, (3) when controlled for normal OHC function, persons exhibiting either high or low ECochG amplitudes exhibited no statistically significant differences in neither speech in quiet nor speech in noise performance, (4) speech in noise performance was correlated with OHC function, (5) hearing impaired subjects with OHC dysfunction exhibited better speech in quiet performance at or near threshold when stimuli were presented at equivalent sensation levels. These results show that OHC dysfunction contributes to hidden hearing loss, OHC function is required for optimum speech in noise performance, and those persons with sensorineural hearing loss exhibit better word discrimination in quiet at or near their audiometric thresholds than normal listeners.

No MeSH data available.


Related in: MedlinePlus