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

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 “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.


Speech in noise performance is correlated with OHC function. Distribution of individual QuickSIN scores plotted as a function DPAOE amplitude (A), DPAOE threshold (B), CAP amplitude when the 4 kHz tone pip is presented at 40 dB SL (C), and 60 dB SL (D), CAP latency at 40 dB SL (E), and CAP threshold (F). As noted in the text, all correlations were statistically significant with the exception of (D). Lines represent best fit (linear).
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Figure 8: Speech in noise performance is correlated with OHC function. Distribution of individual QuickSIN scores plotted as a function DPAOE amplitude (A), DPAOE threshold (B), CAP amplitude when the 4 kHz tone pip is presented at 40 dB SL (C), and 60 dB SL (D), CAP latency at 40 dB SL (E), and CAP threshold (F). As noted in the text, all correlations were statistically significant with the exception of (D). Lines represent best fit (linear).

Mentions: In order to determine which cell types play a role in speech discrimination in the presence of background noise, all of the subjects from each group were used to correlate SIN performance with OHC and AN function (Figure 8). The results indicated that SIN performance was correlated with DPOAE function, where lower QSIN scores (better performance in noise) inversely correlated with DPOAE SNR (maximum τb = −0.522, p = 0.000 at 4 kHz; Figure 8A) and a directly correlated with DPOAE thresholds (maximum τb = 0.378, p = 0.000 at 3 kHz; Figure 8B). To further investigate these correlations, subjects were ranked by QuickSIN scores, and were divided into either Normal SIN (QSIN <1 dB SNR loss) or Poorer SIN (QSIN > 0 dB SNR loss) groups. It should be noted that the manufactures' QSIN cutoff score between normal and mild SIN impairment is 2 dB SNR loss, with 3 dB SNR loss representing “near normal.” However, the new data presented in Figure 5 demonstrates that OHC damage can occur in a person with a hfPTA as low as 15 dB HL, and Figure 3C shows that the QSIN cutoff for normal OHC function is −0.2 ± 0.3 dB SNR loss. Therefore, in order control for hidden hearing loss that was not accounted for by the manufactures of the QSIN, this paper will use a QSIN score of <1 dB SNR loss to differentiate between SIN performance in a non-pathological ear and a QSIN score > 0 dB SNR loss to correspond to an SIN performance in a pathological ear.


Outer Hair Cell and Auditory Nerve Function in Speech Recognition in Quiet and in Background Noise
Speech in noise performance is correlated with OHC function. Distribution of individual QuickSIN scores plotted as a function DPAOE amplitude (A), DPAOE threshold (B), CAP amplitude when the 4 kHz tone pip is presented at 40 dB SL (C), and 60 dB SL (D), CAP latency at 40 dB SL (E), and CAP threshold (F). As noted in the text, all correlations were statistically significant with the exception of (D). Lines represent best fit (linear).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5383716&req=5

Figure 8: Speech in noise performance is correlated with OHC function. Distribution of individual QuickSIN scores plotted as a function DPAOE amplitude (A), DPAOE threshold (B), CAP amplitude when the 4 kHz tone pip is presented at 40 dB SL (C), and 60 dB SL (D), CAP latency at 40 dB SL (E), and CAP threshold (F). As noted in the text, all correlations were statistically significant with the exception of (D). Lines represent best fit (linear).
Mentions: In order to determine which cell types play a role in speech discrimination in the presence of background noise, all of the subjects from each group were used to correlate SIN performance with OHC and AN function (Figure 8). The results indicated that SIN performance was correlated with DPOAE function, where lower QSIN scores (better performance in noise) inversely correlated with DPOAE SNR (maximum τb = −0.522, p = 0.000 at 4 kHz; Figure 8A) and a directly correlated with DPOAE thresholds (maximum τb = 0.378, p = 0.000 at 3 kHz; Figure 8B). To further investigate these correlations, subjects were ranked by QuickSIN scores, and were divided into either Normal SIN (QSIN <1 dB SNR loss) or Poorer SIN (QSIN > 0 dB SNR loss) groups. It should be noted that the manufactures' QSIN cutoff score between normal and mild SIN impairment is 2 dB SNR loss, with 3 dB SNR loss representing “near normal.” However, the new data presented in Figure 5 demonstrates that OHC damage can occur in a person with a hfPTA as low as 15 dB HL, and Figure 3C shows that the QSIN cutoff for normal OHC function is −0.2 ± 0.3 dB SNR loss. Therefore, in order control for hidden hearing loss that was not accounted for by the manufactures of the QSIN, this paper will use a QSIN score of <1 dB SNR loss to differentiate between SIN performance in a non-pathological ear and a QSIN score > 0 dB SNR loss to correspond to an SIN performance in a pathological ear.

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.