Binaural advantages in users of bimodal and bilateral cochlear implant devices.
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ABSTRACT:
SUBMITTER: Kokkinakis K
PROVIDER: S-EPMC3874059 | biostudies-other | 2014 Jan
REPOSITORIES: biostudies-other
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Project description:OBJECTIVES:Binaural pitch fusion is the fusion of stimuli that evoke different pitches between the ears into a single auditory image. Individuals who use hearing aids or bimodal cochlear implants (CIs) experience abnormally broad binaural pitch fusion, such that sounds differing in pitch by as much as 3-4 octaves are fused across ears, leading to spectral averaging and speech perception interference. The goal of this study was to determine if adult bilateral CI users also experience broad binaural pitch fusion. DESIGN:Stimuli were pulse trains delivered to individual electrodes. Fusion ranges were measured using simultaneous, dichotic presentation of reference and comparison stimuli in opposite ears, and varying the comparison stimulus to find the range that fused with the reference stimulus. RESULTS:Bilateral CI listeners had binaural pitch fusion ranges varying from 0 to 12?mm (average 6.1?±?3.9?mm), where 12?mm indicates fusion over all electrodes in the array. No significant correlations of fusion range were observed with any subject factors related to age, hearing loss history, or hearing device history, or with any electrode factors including interaural electrode pitch mismatch, pitch match bandwidth, or within-ear electrode discrimination abilities. CONCLUSIONS:Bilateral CI listeners have abnormally broad fusion, similar to hearing aid and bimodal CI listeners. This broad fusion may explain the variability of binaural benefits for speech perception in quiet and in noise in bilateral CI users.
| S-EPMC5821581 | biostudies-literature
Project description:Although bilateral cochlear implant users receive input to both ears, they nonetheless have relatively poor localization abilities in the horizontal plane. This is likely because of the two binaural cues, they have good sensitivity to interaural differences of level (inter-aural level differences, or ILDs), but not those of time (inter-aural time differences; ITDs). Here, localization performance is assessed in six bilateral cochlear implant patients when instantaneous ITDs are measured and converted to ILDs, a strategy that results in larger-than-typical ILDs. The added ILDs are corrective, in that they are derived from individual listener performance across both frequency and azimuth, so that they are small where a listener performs well, and increase as performance deviates from ideal. Results show significantly improved localization performance as a result of this strategy, with two of the six listeners achieving levels of performance typically observed in NH listeners.
| S-EPMC5774684 | biostudies-literature
Project description:ObjectivesIndividuals who use hearing aids (HAs) or cochlear implants (CIs) can experience broad binaural pitch fusion, such that sounds differing in pitch by as much as 3 to 4 octaves are perceptually integrated across ears. Previously, it was shown in HA users that the fused pitch is a weighted average of the two monaural pitches, ranging from equal weighting to dominance by the lower pitch. The goal of this study was to systematically measure the fused pitches in adult CI users, and determine whether CI users experience similar pitch averaging effects as observed in HA users.DesignTwelve adult CI users (Cochlear Ltd, Sydney, Australia) participated in this study: six bimodal CI users, who wear a CI with a contralateral HA, and six bilateral CI users. Stimuli to HA ears were acoustic pure tones, and stimuli to CI ears were biphasic pulse trains delivered to individual electrodes. Fusion ranges, the ranges of frequencies/electrodes in the comparison ear that were fused with a single electrode (electrode 22, 18, 12, or 6) in the reference ear, were measured using simultaneous, dichotic presentation of reference and comparison stimuli in opposite ears, and varying the comparison stimulus. Once the fusion ranges were measured, the fused binaural pitch of a reference-pair stimulus combination was measured by finding a pitch match to monaural comparison stimuli presented to the paired stimulus ear.ResultsFusion pitch weighting in CI users varied depending on the pitch difference of the reference-pair stimulus combination, with equal pitch averaging occurring for stimuli closer in pitch and lower pitch dominance occurring for stimuli farther apart in pitch. The averaging region was typically 0.5 to 2.3 octaves around the reference for bimodal CI users and 0.4 to 1.5 octaves for bilateral CI users. In some cases, a bias in the averaging region was observed toward the ear with greater stimulus variability.ConclusionsFusion pitch weighting effects in CI users were similar to those observed previously in HA users. However, CI users showed greater inter-subject variability in both pitch averaging ranges and bias effects. These findings suggest that binaural pitch averaging could be a common underlying mechanism in hearing-impaired listeners.
| S-EPMC7501189 | biostudies-literature
Project description:Bilateral cochlear implant (BiCI) users gain an advantage in noisy situations from a second implant, but their bilateral performance falls short of normal hearing listeners. Channel interactions due to overlapping electrical fields between electrodes can impair speech perception, but its role in limiting binaural hearing performance has not been well characterized. To address the issue, binaural masking level differences (BMLD) for a 125 Hz tone in narrowband noise were measured using a pair of pitch-matched electrodes while simultaneously presenting the same masking noise to adjacent electrodes, representing a more realistic stimulation condition compared to prior studies that used only a single electrode pair. For five subjects, BMLDs averaged 8.9 ± 1.0 dB (mean ± s.e.) in single electrode pairs but dropped to 2.1 ± 0.4 dB when presenting noise on adjacent masking electrodes, demonstrating a negative impact of the additional maskers. Removing the masking noise from only the pitch-matched electrode pair not only lowered thresholds but also resulted in smaller BMLDs. The degree of channel interaction estimated from auditory nerve evoked potentials in three subjects was significantly and negatively correlated with BMLD. The data suggest that if the amount of channel interactions can be reduced, BiCI users may experience some performance improvements related to binaural hearing.
| S-EPMC3135149 | biostudies-other
Project description:Many cochlear implant users with binaural residual (acoustic) hearing benefit from combining electric and acoustic stimulation (EAS) in the implanted ear with acoustic amplification in the other. These bimodal EAS listeners can potentially use low-frequency binaural cues to localize sounds. However, their hearing is generally asymmetric for mid- and high-frequency sounds, perturbing or even abolishing binaural cues. Here, we investigated the effect of a frequency-dependent binaural asymmetry in hearing thresholds on sound localization by seven bimodal EAS listeners. Frequency dependence was probed by presenting sounds with power in low-, mid-, high-, or mid-to-high-frequency bands. Frequency-dependent hearing asymmetry was present in the bimodal EAS listening condition (when using both devices) but was also induced by independently switching devices on or off. Using both devices, hearing was near symmetric for low frequencies, asymmetric for mid frequencies with better hearing thresholds in the implanted ear, and monaural for high frequencies with no hearing in the non-implanted ear. Results show that sound-localization performance was poor in general. Typically, localization was strongly biased toward the better hearing ear. We observed that hearing asymmetry was a good predictor for these biases. Notably, even when hearing was symmetric a preferential bias toward the ear using the hearing aid was revealed. We discuss how frequency dependence of any hearing asymmetry may lead to binaural cues that are spatially inconsistent as the spectrum of a sound changes. We speculate that this inconsistency may prevent accurate sound-localization even after long-term exposure to the hearing asymmetry.
| S-EPMC9829999 | biostudies-literature
Project description:OBJECTIVES:In this clinical study, stereo perception of music samples and its contribution to music enjoyment in CI users is investigated. It is studied in free field as well as direct audio presentation. METHODS:20 bilateral and 9 bimodal CI users performed stereo detection tests and music enjoyment ratings. Music was presented either in mono or in stereo in free field or with direct audio presentation. Stereo detection was assessed with a 3-AFC paradigm. Music enjoyment was studied with scale ratings. RESULTS:For bilateral CI users, stereo detection increased from 52% correct in free field to 86% with direct audio presentation. Increased music enjoyment with improved stereo detection was obtained. Bimodal CI users could not identify stereo sounds. Music enjoyment did not increase for stereo presentations in bimodal subjects. DISCUSSION:For bilateral CI users, improved stereo detection might increase music enjoyment with direct audio presentation, which is likely due to bypassing the room acoustics. In bimodal CI users, no clear improvement was found, which is likely attributed due to the different hearing losses and therefore individually different interaural frequency overlaps between the hearing aid and the cochlear implant. CONCLUSION:Direct audio presentation is an efficient method to improve music enjoyment in bilateral CI users.
| S-EPMC7337296 | biostudies-literature
Project description:Bilateral cochlear implants (CIs) have provided some success in improving spatial hearing abilities to patients, but with large variability in performance. One reason for the variability is that there may be a mismatch in the place-of-stimulation arising from electrode arrays being inserted at different depths in each cochlea. Goupell et al. [(2013b). J. Acoust. Soc. Am. 133(4), 2272-2287] showed that increasing interaural mismatch led to non-fused auditory images and poor lateralization of interaural time differences in normal hearing subjects listening to a vocoder. However, a greater bandwidth of activation helped mitigate these effects. In the present study, the same experiments were conducted in post-lingually deafened bilateral CI users with deliberate and controlled interaural mismatch of single electrode pairs. Results show that lateralization was still possible with up to 3 mm of interaural mismatch, even when off-center, or multiple, auditory images were perceived. However, mismatched inputs are not ideal since it leads to a distorted auditory spatial map. Comparison of CI and normal hearing listeners showed that the CI data were best modeled by a vocoder using Gaussian-pulsed tones with 1.5 mm bandwidth. These results suggest that interaural matching of electrodes is important for binaural cues to be maximally effective.
| S-EPMC3799729 | biostudies-other
Project description:This study compared spatial speech-in-noise performance in two cochlear implant (CI) patient groups: bimodal listeners, who use a hearing aid contralaterally to support their impaired acoustic hearing, and listeners with contralateral normal hearing, i.e., who were single-sided deaf before implantation. Using a laboratory setting that controls for head movements and that simulates spatial acoustic scenes, speech reception thresholds were measured for frontal speech-in-stationary noise from the front, the left, or the right side. Spatial release from masking (SRM) was then extracted from speech reception thresholds for monaural and binaural listening. SRM was found to be significantly lower in bimodal CI than in CI single-sided deaf listeners. Within each listener group, the SRM extracted from monaural listening did not differ from the SRM extracted from binaural listening. In contrast, a normal-hearing control group showed a significant improvement in SRM when using two ears in comparison to one. Neither CI group showed a binaural summation effect; that is, their performance was not improved by using two devices instead of the best monaural device in each spatial scenario. The results confirm a "listening with the better ear" strategy in the two CI patient groups, where patients benefited from using two ears/devices instead of one by selectively attending to the better one. Which one is the better ear, however, depends on the spatial scenario and on the individual configuration of hearing loss.
| S-EPMC6669847 | biostudies-literature
Project description:To evaluate monaural beamforming in bimodally aided cochlear implant (CI) users.The study enrolled twelve adult bimodal listeners with at least six months of CI-experience and using a contralateral hearing aid (HA) most of the daytime. Participants were uniformly fitted with the same CI speech processor and HA, giving access to an identical monaural beamformer in both ears. A within-subject repeated measures design evaluated three directional configurations [omnidirectional, asymmetric directivity (in CI alone) and symmetric directivity (in both CI and HA)] in two noise types [stationary and fluctuating]. Bimodal speech reception thresholds (SRT) as well as listening effort ratings were assessed in a diffuse noise field.Symmetric monaural beamforming provided a significant SRT improvement of 2.6 dB SNR, compared to 1.6 dB SNR for asymmetric monaural beamforming. Directional benefits were similarly observed in stationary and fluctuating noise. Directivity did not contribute to less listening effort in addition to improvement in speech intelligibility. Bimodal performance was about 7 dB SNR worse in fluctuating than in stationary noise.Monaural beamforming provided substantial benefit for speech intelligibility in noise for bimodal listeners. The greatest benefit occurred when monaural beamforming was activated symmetrically in both CI and HA. Monaural beamforming does not bridge the gap between bimodal and normal hearing performance, especially in fluctuating noise. Results advocate further bimodal co-operation.This trial was registered in www.trialregister.nl under number NTR4901.
| S-EPMC4990192 | biostudies-literature
Project description:ObjectivesTo compare the sound-source localization, discrimination, and tracking performance of bilateral cochlear implant users with omnidirectional (OMNI) and pinna-imitating (PI) microphone directionality modes.DesignTwelve experienced bilateral cochlear implant users participated in the study. Their audio processors were fitted with two different programs featuring either the OMNI or PI mode. Each subject performed static and dynamic sound field spatial hearing tests in the horizontal plane. The static tests consisted of an absolute sound localization test and a minimum audible angle test, which was measured at eight azimuth directions. Dynamic sound tracking ability was evaluated by the subject correctly indicating the direction of a moving stimulus along two circular paths around the subject.ResultsPI mode led to statistically significant sound localization and discrimination improvements. For static sound localization, the greatest benefit was a reduction in the number of front-back confusions. The front-back confusion rate was reduced from 47% with OMNI mode to 35% with PI mode (p = 0.03). The ability to discriminate sound sources straight to the sides (90° and 270° angle) was only possible with PI mode. The averaged minimum audible angle value for the 90° and 270° angle positions decreased from a 75.5° to a 37.7° angle when PI mode was used (p < 0.001). Furthermore, a non-significant trend towards an improvement in the ability to track moving sound sources was observed for both trajectories tested (p = 0.34 and p = 0.27).ConclusionsOur results demonstrate that PI mode can lead to improved spatial hearing performance in bilateral cochlear implant users, mainly as a consequence of improved front-back discrimination with PI mode.
| S-EPMC7757747 | biostudies-literature