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Predicted effects of sensorineural hearing loss on across-fiber envelope coding in the auditory nervea)
a)Portions of this research were presented at the 33rd Midwinter Meeting of the Association for Research in Otolaryngology, Anaheim, CA, February 2010.
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10.1121/1.3583502
/content/asa/journal/jasa/129/6/10.1121/1.3583502
http://aip.metastore.ingenta.com/content/asa/journal/jasa/129/6/10.1121/1.3583502

Figures

Image of FIG. 1.
FIG. 1.

Model threshold elevations for the selective OHC impairment conditions in the present study. Data points represent the CFs used in this study. For CFs above 1 kHz, a fixed 30-dB loss was approximated by choosing appropriate values of C OHC between 0 and 1 in the model. Threshold shifts less than 30 dB for CFs < 1 kHz represent the maximum amount of OHC loss (i.e., complete OHC loss corresponding to C OHC = 0) produced by the AN model, which has reduced cochlear gain at lower CFs.

Image of FIG. 2.
FIG. 2.

Correlogram analyses of envelope coding within (columns 1 and 2) and across (column 3) spike trains from two chinchilla AN fibers [(A) CFA=827 Hz; (B) CFB=618 Hz; 0.4-octave separation] responding to the same broadband noise. (A),(B) Normalized shuffled autocorrelograms [thick line, e.g., SAC(A+)] and cross-polarity correlogram [thin line, e.g., SCC(A+,A−)]. (C) Shuffled cross-fiber correlogram [thick line, e.g., SCC(A+,B+)] and cross-fiber, cross-polarity correlogram [thin line, e.g., SCC(A+,B−)]. The X denotes characteristic delay (CDSCC = 400 μs), which occurs due to the traveling-wave delay. (D)–(F) Corrected sumcors (see text), which emphasize envelope coding, were based on the average of the cross-polarity and auto- or cross-fiber correlograms. Sumcor peak height [in (D) and (E)] quantifies within-fiber envelope coding. Across-CF envelope coding is quantified with a neural cross-correlation coefficient [ρENV, Eq. ((1))] by comparing the peak heights of sumcor(AB) to sumcor(A) and sumcor(B). Spike train data from Heinz and Swaminathan (2009).

Image of FIG. 3.
FIG. 3.

Model predictions of the effects of SNHL on across-CF coding of envelope for CFs centered at 500 Hz [panel (A)] and 3500 Hz [panel (B)]. Stimuli: Broadband noise; duration: 1.7 s. ρENV is plotted as a function of CF separation. Each data point represents mean ρENV computed over twenty repetitions. Filled circles: Predictions for normal hearing at best modulation levels (BML = 45 dB SPL for 500 Hz and 30 dB SPL for 3500 Hz). Filled diamonds: Predictions for normal hearing at the same sound level as the predictions for the impaired cases (65 dB SPL for 500 Hz and 60 dB SPL for 3500 Hz). Open triangles: OHC damage (21 dB loss for 500 Hz, see Fig. 1; 30 dB loss for 3500 Hz); open squares: 30-dB IHC damage. BML for the impaired case was 65 dB SPL for 500 Hz and 60 dB SPL for 3500 Hz. The smallest CF separation (ΔCF in octaves) at which ρENV dropped to 0.7 is shown using arrows and the values are inset. The NH value in parenthesis represents the NH prediction for the equal-SPL condition.

Image of FIG. 4.
FIG. 4.

Model predictions of the effects of SNHL on across-CF coding of speech envelopes for CFs geometrically centered at 500 Hz. Stimuli: Speech (“A boy fell from the window”), duration: 1.72 s. ρENV is plotted as a function of CF separation for overall envelope [panel (A) 0–300 Hz], syllabic envelope [panel (B) 0–5 Hz], phonemic envelope [panel (C) 5–64 Hz], and periodicity envelope [panel (D) 64–300 Hz]. Each data point represents mean ρENV computed over twenty repetitions. Filled circles: Predictions for NH at BML (40 dB SPL). Filled diamonds: Predictions for NH at the same sound level as the predictions for the impaired cases (65 dB SPL). Open triangles: maximal (21 dB) hearing loss due to OHC damage; Open squares: 30-dB IHC damage. BML for the impaired case was 65 dB SPL. The smallest CF separation (ΔCF in octaves) at which ρENV dropped to 0.7 is shown using arrows and the values are inset. The NH value in parenthesis represents the NH prediction for the equal-SPL condition.

Image of FIG. 5.
FIG. 5.

Degree of cross correlation (DCC) is plotted as a function of SNR for speech in quiet and in noise for each modulation frequency range. (A) syllabic (0–5 Hz); (B) phonemic (5–64 Hz); (C) periodicity (64–300 Hz). Filled symbols represent predictions for NH and open symbols represent predictions for selective OHC impairment.

Image of FIG. 6.
FIG. 6.

DCC as a function of SNR for envelope vocoded speech in quiet and in noise for each modulation frequency range. Figure layout is the same as for Fig. 5.

Tables

Generic image for table
TABLE I.

Predicted cross-channel envelope correlations for different modulation frequency ranges (A: ρENV 0–5 H z, syllabic; B: ρENV 5–64 H z, phonemic; C: ρENV 64–300 H z, periodicity) for speech in quiet and normal hearing. Each cell represents mean ρENV between channels computed over five repetitions. Values printed in bold correspond to coefficients that were above the noise floor. The degree of cross correlation (DCC) is inset for each modulation frequency range, and represents the fraction of cells with significant correlations.

Generic image for table
TABLE II.

Predicted cross-channel envelope correlations for speech in quiet with selective OHC impairment. Table layout is the same as for Table I.

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2011-06-14
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Predicted effects of sensorineural hearing loss on across-fiber envelope coding in the auditory nervea)
http://aip.metastore.ingenta.com/content/asa/journal/jasa/129/6/10.1121/1.3583502
10.1121/1.3583502
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