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. 2015;20(3):183-8.
doi: 10.1159/000375394. Epub 2015 Apr 18.

Interaural level difference cues determine sound source localization by single-sided deaf patients fit with a cochlear implant

Michael F Dorman  1 , Daniel Zeitler, Sarah J Cook, Louise Loiselle, William A Yost, George B Wanna, Rene H Gifford
Affiliations

Interaural level difference cues determine sound source localization by single-sided deaf patients fit with a cochlear implant

Michael F Dorman et al. Audiol Neurootol. 2015.

Abstract

In this report, we used filtered noise bands to constrain listeners' access to interaural level differences (ILDs) and interaural time differences (ITDs) in a sound source localization task. The samples of interest were listeners with single-sided deafness (SSD) who had been fit with a cochlear implant in the deafened ear (SSD-CI). The comparison samples included listeners with normal hearing and bimodal hearing, i.e., with a cochlear implant in 1 ear and low-frequency acoustic hearing in the other ear. The results indicated that (i) sound source localization was better in the SSD-CI condition than in the SSD condition, (ii) SSD-CI patients rely on ILD cues for sound source localization, (iii) SSD-CI patients show functional localization abilities within 1-3 months after device activation and (iv) SSD-CI patients show better sound source localization than bimodal CI patients but, on average, poorer localization than normal-hearing listeners. One SSD-CI patient showed a level of localization within normal limits. We provide an account for the relative localization abilities of the groups by reference to the differences in access to ILD cues.

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Figures

Fig. 1
Fig. 1
Mean thresholds for the acoustically stimulated ear for bimodal patients. Error bars indicate the standard error of the mean.
Fig. 2
Fig. 2
Sound source localization (RMS error) in response to a WB noise stimulus as a function of the test group. Each circle indicates the performance of a single subject. Chance performance (±1 SD) is shaded in grey. The horizontal dotted line indicates the 95th percentile of the localization scores for the normal-hearing listeners. The solid vertical line is drawn to visually segregate the data of the SSD patients from that of the other groups.
Fig. 3
Fig. 3
Sound source localization (RMS error) for SSD-CI patients as a function of stimulus characteristics. Data for the 95th percentile of the localization scores for normal-hearing listeners was taken from Yost et al. [2013].
See this image and copyright information in PMC

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