Electric Hearing Research Articles

Discrimination between sequential and simultaneous virtual channels with electrical hearing

In cochlear implants (CIs), simultaneous or sequential stimulation of adjacent electrodes can produce intermediate pitch percepts between those of the component electrodes. However, it is unclear whether simultaneous and sequential virtual channels (VCs) can be discriminated. In this study, CI users were asked to discriminate simultaneous and sequential VCs; discrimination was measured for monopolar (MP) and bipolar + 1 stimulation (BP + 1), i.e., relatively broad and focused stimulation modes. For sequential VCs, the interpulse interval (IPI) varied between 0.0 and 1.8 ms. All stimuli were presented at comfortably loud, loudness-balanced levels at a 250 pulse per second per electrode (ppse) stimulation rate. On average, CI subjects were able to reliably discriminate between sequential and simultaneous VCs. While there was no significant effect of IPI or stimulation mode on VC discrimination, some subjects exhibited better VC discrimination with BP + 1 stimulation. Subjects' discrimination between sequential and simultaneous VCs was correlated with electrode discrimination, suggesting that spatial selectivity may influence perception of sequential VCs. To maintain equal loudness, sequential VC amplitudes were nearly double those of simultaneous VCs, presumably resulting in a broader spread of excitation. These results suggest that perceptual differences between simultaneous and sequential VCs might be explained by differences in the spread of excitation.

Binaural benefit for speech recognition with spectral mismatch across ears in simulated electric hearing

The present study investigated the effects of binaural spectral mismatch on binaural benefits in the context of bilateral cochlear implants using acoustic simulations. Binaural spectral mismatch was systematically manipulated by simulating changes in the relative insertion depths across ears. Sentence recognition, presented unilaterally and bilaterally, were measured in normal-hearing listeners in quiet and noise at +5 dB signal-to-noise ratio. Significant binaural benefits were observed when the interaural difference in insertion depth was 1 mm or less. This result suggests a dependence of the binaural benefit on redundant speech information, rather than on similarity in performance across ears.

Cochlear infrastructure for electrical hearing

Although the cochlear implant is already the world’s most successful neural prosthesis, opportunities for further improvement abound. Promising areas of current research include work on improving the biological infrastructure in the implanted cochlea to optimize reception of cochlear implant stimulation and on designing the pattern of electrical stimulation to take maximal advantage of conditions in the implanted cochlea. In this review we summarize what is currently known about conditions in the cochlea of deaf, implanted humans and then review recent work from our animal laboratory investigating the effects of preserving or reinnervating tissues on psychophysical and electrophysiological measures of implant function. Additionally we review work from our human laboratory on optimizing the pattern of electrical stimulation to better utilize strengths in the cochlear infrastructure. Histological studies of human temporal bones from implant users and from people who would have been candidates for implants show a range of pathologic conditions including spiral ganglion cell counts ranging from approximately 2% to 92% of normal and partial hair cell survival in some cases. To duplicate these conditions in a guinea pig model, we use a variety of deafening and implantation procedures as well as post-deafening therapies designed to protect neurons and/or regenerate neurites. Across populations of human patients, relationships between nerve survival and functional measures such as speech have been difficult to demonstrate, possibly due to the numerous subject variables that can affect implant function and the elapsed time between functional measures and postmortem histology. However, psychophysical studies across stimulation sites within individual human subjects suggest that biological conditions near the implanted electrodes contribute significantly to implant function, and this is supported by studies in animal models comparing histological findings to psychophysical and electrophysiological data. Results of these studies support the efforts to improve the biological infrastructure in the implanted ear and guide strategies which optimize stimulation patterns to match patient-specific conditions in the cochlea.

Speech and music recognition with acoustic simulations of a harmonic single sideband encoding strategy for cochlear implants.

Cochlear implant users experience difficulties in speech perception in noise and music perception. Previous studies suggested that these difficulties are partially due to the lack of temporal fine structure (TFS) coding in cochlear implants [Moore, JARO (2008)]. TFSs are generally high-frequency signals; therefore, delivering perceivable TFS cues in electrical hearing is a challenge because the temporal sensitivity in cochlear implants is typically restricted to 300 Hz and below. A recently-proposed strategy, harmonic single sideband encoder (HSSE), could potentially use the harmonic structure of sounds to coherently demodulate TFS information [Li et al., ICASSP (2010)]. To evaluate these potential benefits to speech and music perception, this study compared the performance of five normal hearing listeners using four- and eight-channel sinusoidal vocoder simulations of HSSE and the continuous interleaved stimulation (CIS) strategy. Scores on the following tasks were measured: sentence recognition in noise and single-talker maskers, melody and timbre recognition, and Mandarin tone discrimination. In all of the tasks, HSSE listeners obtained a significant performance improvement over the CIS vocoder. Furthermore, simulation results from an electrically-stimulated model of the auditory nerve fibers demonstrated that HSSE is capable of encoding temporal pitch cues better than CIS. [This study was supported by NIH R01-DC007525, P30-DC004661, and T32-DC005361; AFOSR Grant FA9550061019; CGF 657635; ITHS 620491; Advanced Bionics Graduate Fellowship; and NSF TG-IBN090004.]

Benefits of Combined Acoustic and Electric Hearing for Music and Pitch Perception

The total number of cochlear implant (CI) recipients worldwide is now approaching 200,000. Most current CI users attain an adequate ability to understand speech using the implant alone, despite having had at least severe to profound hearing impairment in both ears preoperatively. The satisfactory technical performance of modern CI systems, at least in favorable listening conditions, has resulted in an increasing proportion of CI recipients having usable acoustic hearing postoperatively in one ear, or even in both ears. Many studies have confirmed that, in general, the simultaneous use of acoustic and electric hearing can provide perceptual benefits in comparison to the use of a CI alone. An especially important advantage conferred by the use of acoustic hearing is the potentially improved ability of CI recipients to perceive musical sounds. In particular, the perception of pitch, which is usually not provided adequately by today's CI systems, can be enhanced when sounds are heard acoustically by CI users with sufficient hearing sensitivity.

Identifying emotions in music through electrical hearing in deaf children using cochlear implants

Objective: Cochlear implant (CI) devices are the choice of treatment for individuals with severe to profound hearing loss. The CI devices provide the opportunity for children who are deaf to perceive sound by electrical stimulation of the auditory nerve, with the goal of optimizing oral communication. A natural benefit of acquiring hearing using CIs is the ability to hear, and perhaps enjoy, music. Music is a non-verbal auditory stimulus and a powerful tool for transmitting emotion. Identifying emotional cues is an important part of normal social development and communication and thus music may play an important role in establishing these skills during development. To date, it is not known whether children who use cochlear implants to hear can identify the emotional content carried in music. Our objective in the present study was to determine whether children who have been deaf from infancy and are experienced CI users have acquired the ability to identify emotion in musical phrases.Method: Study participants were 18 CI users (ages 7–13 years) who received right unilateral CIs (mean age at CI activation of 2.9 years) and 18 age-and gender-matched controls. Participants were asked to judge 32 brief musical excerpts as happy or sad by pointing to simple graphics of a smiling or frowning face.Results: Children using CIs were able to correctly distinguish happy versus sad music well above chance levels, but performed more poorly on this task than their peers with typical hearing. Age at CI activation and time since CI activation were both uncorrelated with outcome measures.Conclusion: Children with CIs show the ability to perceive emotion in music but do so less accurately than typically hearing peers.

Acoustic Cues for Consonant Perception with Combined Acoustic and Electric Hearing in Children

Many children who use a cochlear implant in one ear have usable residual hearing in the opposite ear. There is consensus that bilateral stimulation should be provided to these children by fitting a hearing aid in the nonimplanted ear. The combination of acoustic amplification via a hearing aid with electrical stimulation via a cochlear implant is commonly referred to as “bimodal hearing.” This article examines speech perceptual benefits associated with the use of bimodal hearing in children. First, a brief description of the acoustic basis for phonetic contrasts is provided. Second, information on children's consonant perception and information transmission via the use of cochlear implants with or without hearing aids is presented. Finally, a summary of fitting strategies is presented with validation results. These results support the optimization of a hearing aid with a cochlear implant for children.

Hearing Aids and the History of Electronics Miniaturization

Electrical hearing aids were the principal site for component miniaturization and compact assembly before World War II. After the war, hearing aid users became the first consumer market for printed circuits, transistors, and integrated circuits. Due to the stigmatization of hearing loss, users generally demanded small or invisible devices. In addition to being early adopters, deaf and hard of hearing people were often the inventors, retailers, and manufacturers of miniaturized electronics.

Musical pitch and lexical tone perception with cochlear implants

Objective: The purpose of the present study was to test the hypothesis that cochlear implant (CI) users’ music perception is correlated with their lexical tone perception, and the two types of perception share similar mechanisms in electric hearing. Design: A lexical tone perception test and a pitch interval discrimination test were administered to a group of CI users and a group of normal-hearing (NH) listeners. Sample study: Nineteen adult CI users and 10 NH listeners who are native-Mandarin-Chinese speakers participated in the study. Result: Tone-perception performance of the CI group was, on average, 58.3% correct (± 19.78% correct), and performance of the NH group was near perfect. The CI group had a mean threshold of 5.66 semitones (± 5.57 semitones) in pitch discrimination as compared to the threshold of 0.44 semitone from the NH group. There was a strong correlation between the CI users’ tone-perception performance and their pitch discrimination threshold (r = −0.75, p < 0.001). Conclution: Musical and lexical pitch perceptions are strongly correlated with each other and they might share similar mechanisms in electric hearing.SumarioObjetivo: el objetivo de este estudio fue probar la hipótesis de que la percepción de la música en los usuarios de los implantes cocleares (CI) está correlacionada con la percepción del tono léxico y los dos tipos de percepción comparten mecanismos similares en la audición electrónica. Diseño: Una prueba de percepción del tono léxico y una prueba de la discriminación del intervalo de tono se administraron a un grupo de usuarios de implante coclear y a un grupo de sujetos normoyentes (NH). Muestra: Diecinueve adultos usuarios de CI y 10 sujetos normoyentes hablantes nativos del chino mandarín participaron en el estudio. Resultados: El desempeño en la percepción tonal en el grupo de CI fue en promedio 58.3% correcta (±19.78%) y el desempeño del grupo NH fue casi perfecto. El grupo CI tuvo un umbral promedio de 5.66 semitonos (±5.57 semitonos) en discriminación del tono comparado con el umbral de 0.44 semitonos del grupo NH. Hubo una fuerte correlación entre el desempeño de la percepción del tono en los usuarios de CI y su umbral de discriminación de tono (r = −0.75, p < 0.001). Conclusión: El tono musical y el léxico están estrechamente correlacionados entre sí y puede ser que compartan mecanismos similares en la audición eléctrica.

Revision cochlear implantation in children

The cochlear implant intervention is the standard of care for the rehabilitation of severe to profound hearing loss in children. Growing case numbers are associated with increasing prevalence of conditions that may require surgical revision to maintain electrical hearing and language acquisition. Scalp complications can be avoided by observing core surgical principles, which also reduces the risk of wound infections. Providers of cochlear implant care should also become familiar with the indications for revision surgery, including the work-up and appropriate technique for electrode re-insertion. A summary of the literature reveals varied outcomes depending on indication, ranging from diminished speech performance to significant gains after revision surgery. Patient selection must be carefully considered to minimize additional delays in language development. The decision for revision surgery is straightforward in cases of documented speech perception decline, device failure and infection. In cases of failure to progress, however, the outcome may be reduced or unchanged.

Cross-Frequency Integration for Consonant and Vowel Identification in Bimodal Hearing

Improved speech recognition in binaurally combined acoustic-electric stimulation (otherwise known as bimodal hearing) could arise when listeners integrate speech cues from the acoustic and electric hearing. The aims of this study were (a) to identify speech cues extracted in electric hearing and residual acoustic hearing in the low-frequency region and (b) to investigate cochlear implant (CI) users' ability to integrate speech cues across frequencies. Normal-hearing (NH) and CI subjects participated in consonant and vowel identification tasks. Each subject was tested in 3 listening conditions: CI alone (vocoder speech for NH), hearing aid (HA) alone (low-pass filtered speech for NH), and both. Integration ability for each subject was evaluated using a model of optimal integration--the PreLabeling integration model (Braida, 1991). Only a few CI listeners demonstrated bimodal benefit for phoneme identification in quiet. Speech cues extracted from the CI and the HA were highly redundant for consonants but were complementary for vowels. CI listeners also exhibited reduced integration ability for both consonant and vowel identification compared with their NH counterparts. These findings suggest that reduced bimodal benefits in CI listeners are due to insufficient complementary speech cues across ears, a decrease in integration ability, or both.

Temporal and Spectral Cues for Musical Timbre Perception in Electric Hearing

The purpose of this study was to investigate musical timbre perception in cochlear-implant (CI) listeners using a multidimensional scaling technique to derive a timbre space. Methods Sixteen stimuli that synthesized western musical instruments were used (McAdams, Winsberg, Donnadieu, De Soete, & Krimphoff, 1995). Eight CI listeners and 15 normal-hearing (NH) listeners participated. Each listener made judgments of dissimilarity between stimulus pairs. Acoustical analyses that characterized the temporal and spectral characteristics of each stimulus were performed to examine the psychophysical nature of each perceptual dimension. For NH listeners, the timbre space was best represented in three dimensions, one correlated with the temporal envelope (log-attack time) of the stimuli, one correlated with the spectral envelope (spectral centroid), and one correlated with the spectral fine structure (spectral irregularity) of the stimuli. The timbre space from CI listeners, however, was best represented by two dimensions, one correlated with temporal envelope features and the other weakly correlated with spectral envelope features of the stimuli. Temporal envelope was a dominant cue for timbre perception in CI listeners. Compared to NH listeners, CI listeners showed reduced reliance on both spectral envelope and spectral fine structure cues for timbre perception.

Evidence of Technology Impact

Improvements in speech perception with cochlear implants can be demonstrated over more than a quarter of a century; from little more than an aid to lip-reading to supporting open set speech understanding in highly challenging listening situations. Both demographical and technological factors have contributed to this change. Sound processor generations show continuous improvement over a ten year time period when demographical change was much less pronounced. Changes to the quality of the electronics, the electrode array and arguably most importantly, the sound coding strategy have all contributed to the improvement. Within-subject comparisons of algorithms also shows significant speech perception improvement. Beyond speech, interest is being shown in music appreciation. Questionnaire results relating to lyrics, instruments and scene show the Fidelity 120 current steering strategy to be significantly better than conventional processing strategies and not significantly poorer than results from normal hearing listeners. Also, on newer tests better reflecting everyday listening, the best implant users show essentially normal hearing ability. However, much work remains to be done to understand why many implant recipients perform at much lower levels, to improve these outcomes and also the naturalness of electrical hearing.

Adaptation in electric hearing: analysis of level and amplitude modulation encoding

Neural adaptation in sensory systems can potentially improve the efficiency and fidelity of neural encoding (e.g. [1]). In the auditory system, for instance, the firing rates of peripheral and midbrain neurons can shift to better represent the range of most likely stimulus levels [2,3]. Adaptation has long been known to exist throughout the auditory system in response to acoustic stimulation, and now studies have revealed that the auditory nerve exhibits firing rate adaptation in response to electric stimulation [4]. Adaptation may, therefore, have important implications for the function and design of cochlear implants, but there have been few attempts to investigate the relationship between neural adaptation, cochlear implant design, and listening outcomes for cochlear implant users. We hypothesize that it will be possible to identify time scales of adaptation that optimally encode a stimulus, depending on the time scales of the stimulus. The time course of adaptation appears to depend on stimulus parameters [5], so if our hypothesis is true, then it may be possible to design stimulation strategies that induce adaptation in a way that improves encoding of cochlear implant stimuli. To address this hypothesis, we use a point process model to simulate the response of an auditory nerve cell to electric stimulation. The model replicates known features of the auditory nerve’s response to electric stimulation including spike threshold, input/output function, and refractory effects. For this study, we implement firing rate adaptation in the model via a spike-history feedback mechanism. The adaptation component has two parameters that control the time scale and degree of adaptation. We simulate the effect of adaptation on encoding of stimulus level and sinusoidal amplitude modulation. We use the likelihood function associated with the point process model to quantify spike timing information, as well as common measures of spike count information, strength of phase-locking to the amplitude-modulated signal, and signal-to-noise ratio of firing rates. We find that at high stimulus levels, firing rate adaptation prevents saturation and therefore improves sensitivity to level increments and modulation. In response to weaker stimuli, adaptation typically degrades the encoding of level and amplitude modulation. In general, we find that the degree, not time scale, of adaptation is the more important factor in determining the effect of adaptation on encoding. In order to further probe the effects of the time scale of adaptation, we analyze neural encoding of dynamic stimuli that feature multiple time scales and non-stationary levels.

The Use of Frequency Compression by Cochlear Implant Recipients with Postoperative Acoustic Hearing

The number of cochlear implant (CI) recipients who have usable acoustic hearing in at least one ear is continuing to grow. Many such CI users gain perceptual benefits from the simultaneous use of acoustic and electric hearing. In particular, it has been shown previously that use of an acoustic hearing aid (HA) with a CI can often improve speech understanding in noise. To determine whether the application of frequency compression in an HA would provide perceptual benefits to CI recipients with usable acoustic hearing, either when used in combination with the CI or when the HA was used by itself. A repeated-measures experimental design was used to evaluate the effects on speech perception of using a CI either alone or simultaneously with an HA that had frequency compression either enabled or disabled. Eight adult CI recipients who were successful users of acoustic hearing aids in their nonimplanted ears participated as subjects. The speech perception of each subject was assessed in seven conditions. These required each subject to listen with (1) their own HA alone; (2) the Phonak Naida HA with frequency compression (SoundRecover) enabled; (3) the Naida with SoundRecover disabled; (4) their CI alone; (5) their CI and their own HA; (6) their CI and the Naida with SoundRecover enabled; and (7) their CI and the Naida with SoundRecover disabled. Test sessions were scheduled over a period of about 10 wk. During part of that time, the subjects were asked to use the Phonak Naida HA with their CIs in place of their own HAs. The speech perception tests included measures of consonant identification from a closed set of 12 items presented in quiet, and measures of sentence understanding in babble noise. The speech materials were presented at an average level of 60 dB SPL from a loudspeaker. Speech perception was better, on average, in all conditions that included use of the CI in comparison with any condition in which only an HA was used. For example, consonant recognition improved by approximately 50 percentage points, on average, between the HA-alone listening conditions and the CI-alone condition. There were no statistically significant score differences between conditions with SoundRecover enabled and disabled. There was a small but significant improvement in the average signal-to-noise ratio (SNR) required to understand 50% of the words in the sentences presented in noise when an HA was used simultaneously with the CI. Although each of these CI users readily accepted the Phonak Naida HA with SoundRecover frequency compression, no benefits related specifically to the use of SoundRecover were found in the particular tests of speech understanding applied in this study. The relatively high levels of perceptual performance attained by these subjects with use of a CI by itself are consistent with the finding that the addition of an HA provided little further benefit. However, the use of an HA with the CI did provide better performance than the CI alone for understanding sentences in noise.

Comodulation masking release with signal‐masker interactions represented in the envelope.

In normal hearing, the threshold of a tone masked by a modulated narrow‐band on‐frequency masker (OFB) can be reduced if correlated modulation is present on spectrally distant flanking bands (FBs), an effect known as comodulation masking release (CMR). Since electric hearing with current cochlear implants is based on envelope information, comodulation of envelopes on multiple electrodes might also be beneficial for detection in electric hearing. CMR was investigated with normal‐hearing participants listening to unprocessed or vocoded stimuli. In Experiment 1, tone thresholds were determined when masked by a sinusoidally amplitude‐modulated band of noise (SAM and OFB) and by zero to four FBs of noise whose envelopes were either co‐ or anti‐modulated with the OFB envelope. In Experiment 2, envelopes of those signals were extracted in a vocoder and used to modulate noise or sinusoidal carriers, thereby replacing the original temporal fine structure (TFS). Significant CMR of 3–10 dB was found in unprocessed conditions and although reduced to 2–6 dB, CMR was still significant after vocoding. CMR did not differ significantly between the sine and the noise vocoder, suggesting that the applied SAM determined the magnitude of CMR. Since CMR withstands vocoding, comodulation is hoped to improve detection in electric hearing.

Music Perception in Children With Cochlear Implants

AbstractAs a result of the widespread use of cochlear implants, individuals with profound hearing loss now are able to hear sounds ranging from a syllable to a symphony. This form of “electric hearing” has been remarkably successful in providing sound to the deaf population and at least 100,000 implantation procedures have been performed worldwide in more than 80 countries (Clark, 2008). Today, it is routine for post-lingual deafened individuals (one who lost their hearing after normal childhood language acquisition) to achieve high performance on language tests following implantation (Lalwani, Larky, Wareing, Kwast, &amp; Schindler, 1998). Deaf children implanted at an early age with a CI usually develop excellent spoken language skills, with placement into mainstream educational schooling (Francis, Koch, Wyatt, &amp; Niparko, 1999). The overwhelming emphasis on language perception in CI users has led to relative neglect of non-linguistic sound perception. Yet, the auditory world consists of many other sounds besides those of spoken language. Of all non-linguistic sounds, perception of music—particularly pitch and timbre—represents the greatest challenge for implant-mediated listening (Limb, 2006). High-level perception of music rarely is attained through conventional speech processing technology in adults or children. Recent technological advances, however, have increased the processing capabilities of modern CIs and hold great promise for music perception and quality of life for children with cochlear implants (Lassaletta et al., 2007).

A model of the auditory nerve for acoustic- and electric excitation

Event Abstract Back to Event A model of the auditory nerve for acoustic- and electric excitation Michele Nicoletti1*, Marek Rudnicki1 and Werner Hemmert1 1 Technische Universität München, Bernstein Center for Computational Neuroscience, Germany Auditory nerve fibers (ANF) convey information about sound to the central nervous system. For both normal hearing subjects and cochlear implant patients the most drastic step of sound coding for neuronal processing is when the analog signal is converted into discrete nerve-action potentials. As any information lost during this process is no longer available for neural processing, it is important to understand the underlying principles of sound coding in the intact auditory system and the limitations in the case of direct electrical stimulation of the auditory nerve. Here we focus on a model of spiral ganglion type I neurons with Hodgkin-Huxley type ion channels, which are also found in cochlear nucleus neurons. Depending on the task, we model the neurons at different levels of detail. Our results show that for acoustic stimuli, the model provides realistic refractoriness and generates more realistic spike trains compared to a spike generator with absolute and exponentially decaying refractoriness added. Not surprisingly, speech discrimination in electrical hearing is lower than in acoustic hearing. On the other hand, the analysis of transmitted information shows that the temporal precision of coding seems to be very high because at levels well above threshold, action potentials are elicited quasi-deterministic by the electrical stimuli. We argue that CIS strategies a) waste as much as 50% of this information and b) much of the information coded in the time domain can not be retrieved by the neurons in the cochlear nucleus. Acknowledgements Funded within the Munich Bernstein Center for Computational Neuroscience by the German Federal Ministry of Education and Research (reference number 01GQ0441) and MED-EL Innsbruck. Keywords: computational neuroscience Conference: Bernstein Conference on Computational Neuroscience, Berlin, Germany, 27 Sep - 1 Oct, 2010. Presentation Type: Presentation Topic: Bernstein Conference on Computational Neuroscience Citation: Nicoletti M, Rudnicki M and Hemmert W (2010). A model of the auditory nerve for acoustic- and electric excitation. Front. Comput. Neurosci. Conference Abstract: Bernstein Conference on Computational Neuroscience. doi: 10.3389/conf.fncom.2010.51.00104 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 06 Sep 2010; Published Online: 23 Sep 2010. * Correspondence: Dr. Michele Nicoletti, Technische Universität München, Bernstein Center for Computational Neuroscience, München, Germany, michele.nicoletti@tum.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Michele Nicoletti Marek Rudnicki Werner Hemmert Google Michele Nicoletti Marek Rudnicki Werner Hemmert Google Scholar Michele Nicoletti Marek Rudnicki Werner Hemmert PubMed Michele Nicoletti Marek Rudnicki Werner Hemmert Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Effect of age at onset of deafness on binaural sensitivity in electric hearing in humans

Sensitivity to binaural cues was studied in 11 bilateral cochlear implant users, all of whom received both of their cochlear implants as adults, but who varied in the age at onset of deafness, from pre-lingual to childhood-onset to adult-onset. Sensitivity to interaural timing difference (ITD) and interaural level difference (ILD) cues was measured at basal, middle, and apical pitch-matched places of stimulation along the cochlear arrays, using a stimulation rate of 100 Hz. Results show that there is a trend for people whose onset of deafness occurred during adult life or late childhood to retain at least some sensitivity to ITDs, whereas people with onset of deafness earlier in life were insensitive to ITDs. In contrast, ILD cue sensitivity was present in all subjects. There were no effects of place of stimulation on binaural sensitivity, suggesting that there is no indication of a dependence of ITD sensitivity on apical vs basal electrode location.

Benefits of Localization and Speech Perception with Multiple Noise Sources in Listeners with a Short-Electrode Cochlear Implant

Research suggests that for individuals with significant low-frequency hearing, implantation of a short-electrode cochlear implant may provide benefits of improved speech perception abilities. Because this strategy combines acoustic and electrical hearing within the same ear while at the same time preserving low-frequency residual acoustic hearing in both ears, localization abilities may also be improved. However, very little research has focused on the localization and spatial hearing abilities of users with a short-electrode cochlear implant. The purpose of this study was to evaluate localization abilities for listeners with a short-electrode cochlear implant who continue to wear hearing aids in both ears. A secondary purpose was to document speech perception abilities using a speech-in-noise test with spatially separate noise sources. Eleven subjects that utilized a short-electrode cochlear implant and bilateral hearing aids were tested on localization and speech perception with multiple noise locations using an eight-loudspeaker array. Performance was assessed across four listening conditions using various combinations of cochlear implant and/or hearing aid use. Results for localization showed no significant difference between using bilateral hearing aids and bilateral hearing aids plus the cochlear implant. However, there was a significant difference between the bilateral hearing aid condition and the implant plus use of a contralateral hearing aid for all 11 subjects. Results for speech perception showed a significant benefit when using bilateral hearing aids plus the cochlear implant over use of the implant plus only one hearing aid. Combined use of both hearing aids and the cochlear implant show significant benefits for both localization and speech perception in noise for users with a short-electrode cochlear implant. These results emphasize the importance of low-frequency information in two ears for the purpose of localization and speech perception in noise.