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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.


Subjects performing better in noise were younger with better audiometric thresholds and better OHC functions. (A) Subjects were ranked by QuickSIN scores, and divided into either Normal SIN (QSIN <1 dB SNR loss, shaded box) or Poorer SIN (QSIN > 0 dB SNR loss) groups as described in the text. Line represents best fit. (B) Box and whisker plots show statistically significant differences between these groups. Open circle represents suspected outliers, and numbers indicate the subject identification of the suspected outlier. Further comparison between these groups showed that those performing better in nose were younger (C) and exhibited better (lower) pure tone thresholds (D). There were no clinically significant differences word recognition in quiet between these groups (E). Persons performing better in the presence of background noise also exhibited more robust DPOAE SNRs (F) and lower DPOAE thresholds (G). This group also exhibited lower CAP amplitude at 40 dB SL (H; compare with the normal line in Figure 6A), longer CAP latencies (I), and lower CAP thresholds (J). *Statistically significant difference between groups.
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Figure 9: Subjects performing better in noise were younger with better audiometric thresholds and better OHC functions. (A) Subjects were ranked by QuickSIN scores, and divided into either Normal SIN (QSIN <1 dB SNR loss, shaded box) or Poorer SIN (QSIN > 0 dB SNR loss) groups as described in the text. Line represents best fit. (B) Box and whisker plots show statistically significant differences between these groups. Open circle represents suspected outliers, and numbers indicate the subject identification of the suspected outlier. Further comparison between these groups showed that those performing better in nose were younger (C) and exhibited better (lower) pure tone thresholds (D). There were no clinically significant differences word recognition in quiet between these groups (E). Persons performing better in the presence of background noise also exhibited more robust DPOAE SNRs (F) and lower DPOAE thresholds (G). This group also exhibited lower CAP amplitude at 40 dB SL (H; compare with the normal line in Figure 6A), longer CAP latencies (I), and lower CAP thresholds (J). *Statistically significant difference between groups.

Mentions: The distribution of QSIN scores were roughly divided in half at 0 SNR Loss (Figure 9A), where 25 subjects performed better in background noise (Normal SIN) and 28 subjects performed worse in background noise (Poorer SIN). J-T testing showed that the group performing better in background noise had statistically significantly lower QuickSIN scores (QSIN = −1.0 ± 0.19 SNR loss vs. 3.4 ± 0.43 SNR loss), which provides confidence that there is a statistically significant difference (p = 0.000) in performance in background noise between these groups (Figure 9B). Subjects performing better in background noise were statistically significantly younger (mean = 39.7 ± 2.71 years vs. 52.6 ± 3.71 years, p = 0.022; Figure 9C) and had statistically significantly lower audiometric thresholds (hfPTA = 10.0 ± 2.29 dB HL) compared to subjects with poorer performance in background noise (mean = 33.6 ± 2.71 dB HL PTA, p = 0.00), with the latter group exhibiting a mild sloping SNHL above 1 kHz (Figure 9D). There were no clinically significant differences in word recognition in quiet between these two groups when NU-6 word lists were presented at any sensation levels (Figure 9E).


Outer Hair Cell and Auditory Nerve Function in Speech Recognition in Quiet and in Background Noise
Subjects performing better in noise were younger with better audiometric thresholds and better OHC functions. (A) Subjects were ranked by QuickSIN scores, and divided into either Normal SIN (QSIN <1 dB SNR loss, shaded box) or Poorer SIN (QSIN > 0 dB SNR loss) groups as described in the text. Line represents best fit. (B) Box and whisker plots show statistically significant differences between these groups. Open circle represents suspected outliers, and numbers indicate the subject identification of the suspected outlier. Further comparison between these groups showed that those performing better in nose were younger (C) and exhibited better (lower) pure tone thresholds (D). There were no clinically significant differences word recognition in quiet between these groups (E). Persons performing better in the presence of background noise also exhibited more robust DPOAE SNRs (F) and lower DPOAE thresholds (G). This group also exhibited lower CAP amplitude at 40 dB SL (H; compare with the normal line in Figure 6A), longer CAP latencies (I), and lower CAP thresholds (J). *Statistically significant difference between groups.
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Figure 9: Subjects performing better in noise were younger with better audiometric thresholds and better OHC functions. (A) Subjects were ranked by QuickSIN scores, and divided into either Normal SIN (QSIN <1 dB SNR loss, shaded box) or Poorer SIN (QSIN > 0 dB SNR loss) groups as described in the text. Line represents best fit. (B) Box and whisker plots show statistically significant differences between these groups. Open circle represents suspected outliers, and numbers indicate the subject identification of the suspected outlier. Further comparison between these groups showed that those performing better in nose were younger (C) and exhibited better (lower) pure tone thresholds (D). There were no clinically significant differences word recognition in quiet between these groups (E). Persons performing better in the presence of background noise also exhibited more robust DPOAE SNRs (F) and lower DPOAE thresholds (G). This group also exhibited lower CAP amplitude at 40 dB SL (H; compare with the normal line in Figure 6A), longer CAP latencies (I), and lower CAP thresholds (J). *Statistically significant difference between groups.
Mentions: The distribution of QSIN scores were roughly divided in half at 0 SNR Loss (Figure 9A), where 25 subjects performed better in background noise (Normal SIN) and 28 subjects performed worse in background noise (Poorer SIN). J-T testing showed that the group performing better in background noise had statistically significantly lower QuickSIN scores (QSIN = −1.0 ± 0.19 SNR loss vs. 3.4 ± 0.43 SNR loss), which provides confidence that there is a statistically significant difference (p = 0.000) in performance in background noise between these groups (Figure 9B). Subjects performing better in background noise were statistically significantly younger (mean = 39.7 ± 2.71 years vs. 52.6 ± 3.71 years, p = 0.022; Figure 9C) and had statistically significantly lower audiometric thresholds (hfPTA = 10.0 ± 2.29 dB HL) compared to subjects with poorer performance in background noise (mean = 33.6 ± 2.71 dB HL PTA, p = 0.00), with the latter group exhibiting a mild sloping SNHL above 1 kHz (Figure 9D). There were no clinically significant differences in word recognition in quiet between these two groups when NU-6 word lists were presented at any sensation levels (Figure 9E).

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.