Auditory Spatial Discrimination and Sound Localization in Single-Sided Deaf Participants Provided with a Cochlear Implant.

INTRODUCTION: Spatial hearing is most accurate using both ears, but accuracy decreases in persons with asymmetrical hearing between ears. In participants with deafness in one ear but normal hearing in the other ear (single-sided deafness [SSD]), this difference can be compensated by a unilateral cochlear implant (CI). It has been shown that a CI can restore sound localization performance, but it is still unclear to what extent auditory spatial discrimination can be improved. METHODS: The present study investigated auditory spatial discrimination using minimum audible angles (MAAs) in 18 CI-SSD participants. Results were compared to 120 age-matched normal-hearing (NH) listeners. Low-frequency (LF) and high-frequency (HF) noise bursts were presented from 4°, 30°, and 60° azimuth on the CI side and on the NH side. MAA thresholds were tested for correlation with localization performance in the same participants. RESULTS: There were eight good performers and ten poor performers. There were more poor performers for LF signals than for HF signals. Performance on the CI side was comparable to performance on the NH side. Most difficulties occurred at 4° and at 30°. Eight of the good performers in the localization task were also good performers in the MAA task. Only the localization ability at 4° on the CI side was positively correlated with the MAA at that location. CONCLUSION: Our data suggest that a CI can restore localization ability but not necessarily auditory spatial discrimination at the same time. The ability to discriminate between adjacent locations may be trainable during rehabilitation to enhance important auditory skills.

Sound Localization in Single-Sided Deaf Participants Provided With a Cochlear Implant.

Spatial hearing is crucial in real life but deteriorates in participants with severe sensorineural hearing loss or single-sided deafness. This ability can potentially be improved with a unilateral cochlear implant (CI). The present study investigated measures of sound localization in participants with single-sided deafness provided with a CI. Sound localization was measured separately at eight loudspeaker positions (4°, 30°, 60°, and 90°) on the CI side and on the normal-hearing side. Low- and high-frequency noise bursts were used in the tests to investigate possible differences in the processing of interaural time and level differences. Data were compared to normal-hearing adults aged between 20 and 83. In addition, the benefit of the CI in speech understanding in noise was compared to the localization ability. Fifteen out of 18 participants were able to localize signals on the CI side and on the normal-hearing side, although performance was highly variable across participants. Three participants always pointed to the normal-hearing side, irrespective of the location of the signal. The comparison with control data showed that participants had particular difficulties localizing sounds at frontal locations and on the CI side. In contrast to most previous results, participants were able to localize low-frequency signals, although they localized high-frequency signals more accurately. Speech understanding in noise was better with the CI compared to testing without CI, but only at a position where the CI also improved sound localization. Our data suggest that a CI can, to a large extent, restore localization in participants with single-sided deafness. Difficulties may remain at frontal locations and on the CI side. However, speech understanding in noise improves when wearing the CI. The treatment with a CI in these participants might provide real-world benefits, such as improved orientation in traffic and speech understanding in difficult listening situations.

[The sensitivity and specificity of the Mini-Audio-Test (MAT) for different levels of hearing loss]. / Die Sensitivität und Spezifität des Mini-Audio-Tests (MAT) für unterschiedliche Hörverlustschwellen.

BACKGROUND: An untreated hearing impairment could have a severe influence on the morbidity. The Mini-Audio-Test (MAT) has been developed for early detecting of a relevant hearing loss. This follow-up investigation should determine the sensitivity, specificity, and the predictive values for a minimum-level of detected hearing loss of 25, 30, 35, and 40 dB, both, in one octave-frequency between 0.5 and 4 kHz and the average of hearing loss for these four frequencies. METHODS: This survey uses data which were collected in 2016 and 2017. 943 patients parted into two groups (aged 50 to 59 years and aged 60 years and more), were investigated using the MAT. Statistical analysis on the sensitivity, specificity, and predictive values in respect were done as proportions together with the 95 %-confidence interval by a logistic regression. RESULTS: The sensitivity of the MAT was increasing in both groups of age by increasing the minimum of to be detected hearing loss. The specificity was decreasing as well, but less. The positive predictive values were higher for the older age-group and are decreasing by increasing of the minimum of to be detected hearing loss. In general, the values using the averaged hearing loss are noticeably lower than for the single frequency detecting. The values for the negative predictive values were contrary. CONCLUSION: The results for persons aged 60 years and more are worse than for the younger. Therefore, a first screening on hearing loss starting at the age of 50 years seems to be recommended urgently. Only by this, a sufficient rehabilitation of the hearing loss could be done in time so that the negative consequences of an untreated hearing impairment could be influenced positively.

Comparison of a Mid Scala and a Perimodiolar Electrode in Adults: Performance, Impedances, and Psychophysics.

OBJECTIVES: The HiFocus Mid-Scala electrode array (HFms) is designed to sit within the scala tympani without touching either the lateral wall or the modiolus. The aim of this study was to compare the HFms to the Helix perimodiolar electrode array. METHOD: Two groups of recipients with Helix (n = 22 ears) and HFms (n = 29 ears) electrode arrays were retrospectively identified and matched by age at implantation and duration of severe to profound deafness. Most comfortable listening levels (M), impedances, Freiburger Monosyllables in quiet, and Oldenburg sentences in adaptive noise were compared at 3, 6, and 12 months postimplant. RESULTS: Median scores for monosyllables in quiet for the HFms group were significantly better than the Helix group at each test interval (p < 0.05). Speech perception in quiet also significantly improved from 3 to 12 months for both groups (p < 0.001). There was no significant difference between the groups for speech in noise. Impedances were significantly lower for the HFms group at 12 months (p < 0.05) except at the basal end and M levels were generally higher. CONCLUSIONS: The HFms group had better median performance for monosyllables in quiet than the Helix group at each test interval, although performance in noise was similar. For speech in noise, the HFms group appear to reach optimum performance quicker than the Helix group. Impedances were lower in the HFms group across the array, other than at the most basal end, and support our hypothesis that the HFms assumes a more lateral position within the cochlea than the Helix electrode, although our article did not include imaging data.

Electric acoustic stimulation (EAS) with the Naída CI Q90 sound processor in experienced cochlear implant users.

Objectives: The benefit of using the electroacoustic functionality was tested compared to electric stimulation alone. Two different cut-off frequencies between acoustic and electric stimulation were tried. Methods: Performance and subjective preference in 10 subjects was measured with electric only and electroacoustic stimulation with two settings: a cut-off for acoustic amplification at the frequency where thresholds exceeded 70 dB and 85 dB. An overlapping setting was also tried in five participants. Results: There was a non-significant trend with a median improvement in SRT of 1.3 dB (70 dB cut-off) and 0.8 dB (85 dB cut-off) compared to the electric only condition. From nine subjects who completed the study, one preferred the 85 dB cut-off frequency, with the others preferred either a 70 dB cut-off or an overlapping setting. Discussion: Nine subjects continued to use the EAS processor after study termination because of subjective benefits. The variability in speech outcomes and subjective preference is underlining the importance of being able to manually change acoustic and electric cut-off frequencies. Conclusion: There were non-significant median group benefits from use of the acoustic component for these existing CI users. A hearing loss of 70 dB HL is an appropriate default cut-off frequency in the fitting software.

Evaluation of a wireless contralateral routing of signal (CROS) device with the Advanced Bionics Naída CI Q90 sound processor.

Objectives: Cochlear implants (CIs) usually provide severe to profoundly deaf recipients with speech intelligibility in quiet. In difficult listening situations such as background noise however, communication often remains challenging. For unilateral CI recipients with a bilateral hearing loss, speech intelligibility for speech sources on the non-implanted side is further impaired by the head-shadow effect. One possibility to overcome this impairment is the use of Contralateral Routing of Signal (CROS) systems, which capture sounds from the non-implanted side and (wirelessly) transmit them to the implant processor, therefore increasing audibility. Such a CROS system was evaluated in this study. Methods: Speech intelligibility in noise was measured in several spatial listening setups using the Oldenburg matrix sentence test in ten cochlear implant users. Performance was compared between listening with the CI alone and listening with the CI in combination with a wireless CROS device. Following an extended trial phase, subjective feedback regarding the device benefit in everyday life was collected via the Bern Benefit in Single Sided Deafness (BBSS) questionnaire. Results: The addition of the wireless CROS device significantly improved speech intelligibility by 7.2 dB (median) in spatial noise. Using advanced directional microphones, a statistically significant benefit of 4.4 dB (median) could be shown in a diffuse noise field. Responses to the BBSS questionnaire revealed that subjects perceived benefit in their everyday lives when using the CROS device with their CI. Conclusion: The investigated CROS system presents a valuable addition to a unilateral CI in cases where bilateral implantation is not an option.

Benefit of directional microphones for unilateral, bilateral and bimodal cochlear implant users.

OBJECTIVE: To compare the standard T-Mic setting to UltraZoom and StereoZoom in 10 unilateral cochlear implant (CI) users, 10 bimodal device users and 10 bilateral CI users as well as a normal hearing (NH) reference group (n = 10). METHOD: Speech reception thresholds were measured using the Oldenburg sentence test in noise. Speech was presented from the front at 0°, noise was presented from five loudspeakers spaced at ±60°, ±120°, 180° (setup A) or from four loudspeakers in the front hemisphere at ±30°, ±60° and one at 180° (setup B). RESULTS: There was a significant advantage for UltraZoom and StereoZoom for all groups in both setups. The largest advantage was for StereoZoom in the bilateral group (setup A, 5.2 dB, P < 0.001 and B, 3.4 dB, P < 0.001) There was a significant advantage for StereoZoom over UltraZoom in the bimodal group (setup A, P < 0.01 and B, P < 0.05) and in the bilateral group (P < 0.01, setup B only). The bilateral group performed as well as the normally hearing group in both setups and the bimodal group performed as well in setup A. There was a significant benefit of 1.8 dB for ClearVoice over UltraZoom alone for the unilateral group. CONCLUSIONS: UltraZoom and StereoZoom provided a clinically and statistically significant benefit over the T-Mic condition. The largest gain was shown for StereoZoom in the bimodal and bilateral groups. The use of StereoZoom enabled the bilateral group to perform as well as the normally hearing group in both the challenging speaker setups. However, real life environments might provide an even greater challenge than the conditions tested here.

[The Mini-Audio-Test (MAT) - a screening method on hearing impairment to be used by general practitioners and specialized physicians]. / Der Mini-Audio-Test (MAT) ­ eine Screeningmethode auf Schwerhörigkeit für Haus- und Fachärzte.

BACKGROUND: In Germany, about 15 million people are suffering from hearing loss (HL), whereas only 16 % are using hearing aids. Untreated hearing loss may lead to severe complications (e. g. social isolation, depression, progress of dementia). An early and widespread screening, beginning at the age of 50, is meant to improve this shortage in medical care. By this study, the Mini-Audio-Test (MAT), a six-question and three-step answers containing questionnaire on subjective HL, should be verified on a normal collective of subjects (sensitivity (Se), specificity (Sp), positive predictive value (Ppv)). METHODS: 943 subjects (older 50 years) without any history of ear disease answered the MAT and received pure-tone audiometry. The Se, Sp, and Pv to detect a relevant HL with the MAT for the age-group < 60 years (AG1) and ≥ 60 years (AG2) were determined. RESULTS: The Se for AG1 was 0.66, the Sp 0.61, the Ppv 0.60, for AG2 the Se was 0.47, the Sp 0.80, the Ppv 0,89. CONCLUSION: Following our results, the MAT is recommended as a general screening-tool for HL in patients over 50 years of age for general practitioners. Hereby, severe secondary diseases (loss of cognitive power, risk of fall, depression, dementia) could be influenced positively.

Binaural interaction in the auditory brainstem response: a normative study.

OBJECTIVE: Binaural interaction can be investigated using auditory evoked potentials. A binaural interaction component can be derived from the auditory brainstem response (ABR-BIC) and is considered evidence for binaural interaction at the level of the brainstem. Although click ABR-BIC has been investigated thoroughly, data on 500 Hz tone-burst (TB) ABR-BICs are scarce. In this study, characteristics of click and 500 Hz TB ABR-BICs are described. Furthermore, reliability of both click and 500 Hz TB ABR-BIC are investigated. METHODS: Eighteen normal hearing young adults (eight women, ten men) were included. ABRs were recorded in response to clicks and 500 Hz TBs. ABR-BICs were derived by subtracting the binaural response from the sum of the monaural responses measured in opposite ears. RESULTS: Good inter-rater reliability is obtained for both click and 500 Hz TB ABR-BICs. The most reliable peak in click ABR-BIC occurs at a mean latency of 6.06 ms (SD 0.354 ms). Reliable 500 Hz TB ABR-BIC are obtained with a mean latency of 9.47 ms (SD 0.678 ms). Amplitudes are larger for 500 Hz TB ABR-BIC than for clicks. CONCLUSION: The most reliable peak in click ABR-BIC occurs at the downslope of wave V. Five hundred Hertz TB ABR-BIC is characterized by a broad positivity occurring at the level of wave V. SIGNIFICANCE: The ABR-BIC is a useful technique to investigate binaural interaction in certain populations. Examples are bilateral hearing aid users, bilateral cochlear implant users and bimodal listeners. The latter refers to the combination of unilateral cochlear implantation and contralateral residual hearing. The majority of these patients have residual hearing in the low frequencies. The current study suggests that 500 Hz TB ABR-BIC may be a suitable technique to assess binaural interaction in this specific population of cochlear implant users.

Assessment of 'Fitting to Outcomes Expert' FOX™ with new cochlear implant users in a multi-centre study.

OBJECTIVE: To compare the fitting time requirements and the efficiency in achieving improvements in speech perception during the first 6 months after initial stimulation of computer-assisted fitting with the Fitting to Outcome eXpert' (FOX) and a standard clinical fitting procedure. METHOD: Twenty-seven post-lingually deafened adults, newly implanted recipients of the Advanced Bionics HiRes 90K™ cochlear implant from Germany, the UK, and France took part in a controlled, randomized, clinical study. Speech perception was measured for all participants and fitting times were compared across groups programmed using FOX and conventional programming methods. RESULTS: The fitting time for FOX was significantly reduced at 14 days (P < 0.001) but equivalent over the 6-month period. The groups were not well matched for duration of deafness; therefore, speech perception could not be compared across groups. DISCUSSION: Despite including more objective measures of performance than a standard fitting approach and the adjustment of a greater range of parameters during initial fitting, FOX did not add to the overall fitting time when compared to the conventional approach. FOX significantly reduced the fitting time in the first 2 weeks and by providing a standard fitting protocol, reduced variability across centres. CONCLUSIONS: FOX computer-assisted fitting can be successfully used at switch on, in different clinical environments, reducing fitting time in the first 2 weeks and is efficient at providing a usable program.

Evaluation of Neural Response Telemetry (NRT™) with focus on long-term rate adaptation over a wide range of stimulation rates.

Custom Sound EP™ (CSEP) is an advanced flexible software tool dedicated to recording of electrically evoked compound action potentials (ECAPs) in Nucleus® recipients using Neural Response Telemetry™ (NRT™). European multi-centre studies of the Freedom™ cochlear implant system confirmed that CSEP offers tools to effectively record ECAP thresholds, amplitude growth functions, recovery functions, spread of excitation functions, and rate adaptation functions and an automated algorithm (AutoNRT™) to measure threshold profiles. This paper reports on rate adaptation measurements. Rate adaptation of ECAP amplitudes can successfully be measured up to rates of 495 pulses per second (pps) by repeating conventional ECAP measurements and over a wide range of rates up to 8000 pps using the masked response extraction technique. Rate adaptation did not show a predictable relationship with speech perception and coding strategy channel rate preference. The masked response extraction method offers opportunities to study long-term rate adaptation with well-defined and controlled stimulation paradigms.

International classification of reliability for implanted cochlear implant receiver stimulators.

OBJECTIVE: To design an international standard to be used when reporting reliability of the implanted components of cochlear implant systems to appropriate governmental authorities, cochlear implant (CI) centers, and for journal editors in evaluating manuscripts involving cochlear implant reliability. STUDY DESIGN: The International Consensus Group for Cochlear Implant Reliability Reporting was assembled to unify ongoing efforts in the United States, Europe, Asia, and Australia to create a consistent and comprehensive classification system for the implanted components of CI systems across manufacturers. SETTING: All members of the consensus group are from tertiary referral cochlear implant centers. INTERVENTIONS: None. MAIN OUTCOME MEASURE: A clinically relevant classification scheme adapted from principles of ISO standard 5841-2:2000 originally designed for reporting reliability of cardiac pacemakers, pulse generators, or leads. RESULTS: Standard definitions for device failure, survival time, clinical benefit, reduced clinical benefit, and specification were generated. Time intervals for reporting back to implant centers for devices tested to be "out of specification," categorization of explanted devices, the method of cumulative survival reporting, and content of reliability reports to be issued by manufacturers was agreed upon by all members. The methodology for calculating Cumulative survival was adapted from ISO standard 5841-2:2000. CONCLUSION: The International Consensus Group on Cochlear Implant Device Reliability Reporting recommends compliance to this new standard in reporting reliability of implanted CI components by all manufacturers of CIs and the adoption of this standard as a minimal reporting guideline for editors of journals publishing cochlear implant research results.

Effect of changing pulse rate on profile parameters of perceptual thresholds and loudness comfort levels and relation to ECAP thresholds in recipients of the Nucleus CI24RE device.

The Nucleus CI24RE 'Freedom' device offers higher stimulation rates and lower noise levels in action potential measurements (ECAPs) than previous devices. A study including ten European implant teams showed that the effect of changes in rate from 250 to 3500 pulses per second on tilt and curvature of the T and C profiles is insignificant. When changing rate one may change the levels at all electrodes by the same amount. Using an automated procedure ECAPs could be measured quickly and reliably at a noise level of only 1 microV, this did not result in improved correlations between the tilt and curvature parameters of the ECAP profiles and those of the T and C profiles. Average C levels appear to differ markedly among implant centers; a better assessment protocol is required. When increasing stimulus rate one should take into account that this requires higher pulse charges per second and more power consumption.

Speech perception performance as a function of stimulus pulse rate and processing strategy preference for the Cochlear Nucleus CI24RE device: relation to perceptual threshold and loudness comfort profiles.

Current cochlear implants can operate at high pulse rates. The effect of increasing pulse rate on speech performance is not yet clear. Habituation to low rates may affect the outcome. This paper presents the results of three subsequent studies using different experimental paradigms, applying the Nucleus CI24RE device, and conducted by ten European implant teams. Pulse rate per channel varied from 500 to 3500 pulses per second with ACE and from 1200 to 3500 pps with CIS strategy. The results showed that the first rate presented had little effect on the finally preferred rate. Lower rates were preferred. The effect of pulse rate on word scores of post-linguistic implantees was small; high rates tended to give lower scores. However, there were no significant differences between the word scores across subjects if collected at the individually preferred pulse rate. High pulse rates were preferred when the post-implantation threshold was low.

The Advanced Bionics High Resolution Mode: stimulation rates up to 5000 pps.

CONCLUSION: The technology of stimulation rates between 1500 and 5000 pulses per second per channel (pps/ch) brings a benefit for all users. However, the fastest possible rate does not necessarily lead to best hearing performance in each individual subject. Individual optimization of stimulation rate is recommended. OBJECTIVES: The aim of this study was to investigate the effect of high stimulation rates on speech perception ability. SUBJECTS AND METHODS: Thirteen subjects with at least 3 months of experience with conventional Clarion speech coding strategies were recruited into cross-over studies. The first study investigated stimulation rates of 1500, 2000 and 3000 pps/ch, the second study investigated rates of 2500 and 5000 pps/ch. Speech perception data were collected for testing in quiet and in competing noise. RESULTS: On average, speech perception performance increased significantly when changing from conventional speech coding strategies to High Resolution Mode. Subjects who preferred continous interleaved sampling (CIS) in standard mode appeared to obtain better results with rates of 2500 or 3000 pps/ch than with 5000 pps/ch. The stimulation rate that led to best performance provided the highest stimulation current efficiency in the majority of subjects.

A high rate n-of-m speech processing strategy for the first generation Clarion cochlear implant.

An n-of-m speech coding strategy has been developed for the Clarion Cochlear Implant Series 1.x (1.0 & 1.2). The basic principle is to reduce the number of stimuli per cycle, by neglecting the less significant spectral components, and to concentrate on the more dominant frequency bands. In this study 20 subjects, implanted with a Clarion device, used an n-of-m strategy at 1666 pps per channel. The outcomes using this strategy were compared with the outcomes using conventional processing (CIS at 833 pps/channel). Eight of the 20 subjects underwent additional testing with the n-of-m strategy with the rate set at 833 pps/channel. Using the n-of-m strategy at 1666 pps showed statistically significant improvement in performance over the CIS strategy, with 16 of the 20 subjects achieving better results. However, there was no statistically meaningful difference in performance between n-of-m at 833 pps and the CIS strategy running at the same rate. Results therefore suggest that n-of-m strategy can be an alternative to CIS, particularly when the implant hardware limits the overall stimulation rate.

A review of device failure in more than 23 years of clinical experience of a cochlear implant program with more than 3,400 implantees.

BACKGROUND: During the last 25 years, the cochlear implant (CI), an active implantable assistive hearing device designed to provide electrical stimulation to the inner ear of the profoundly hearing-impaired individual, has been provided to more than 150,000 recipients worldwide. More recently, implants have been placed in young children as young as 6 months old. With the expectation of lifelong implant use, as with all active implantable medical devices, CI device failure is an inherent risk. Comprehensive, transparent, and comparable information on the incidence of device failure is essential to support individual CI candidate decisions and that of those responsible for the CI program. METHODS: An examination and analysis of our internal electronic database for more than 23 years of CI implant procedures in 3,417 recipients were performed. The cause and incidence of device failure per model and implant type were reported as cumulative survival rates (CSRs). RESULTS: Our experience shows that at 6 years postimplant, there are significant differences in percent CSR and failure modes between implant CI models and CI brands for children and adult CI users. Typically, the percent CSR has increased for successive generations of implant models but not without exception. Failure modes are most commonly related to impact, electronic dysfunction, or leakage. After device failure, explant-reimplant is a safe and acceptable treatment option. CONCLUSION: Percent CSR for CI devices at comparable postimplant time intervals varies, and as such, this information should continue to be carefully and systematically monitored and used by clinicians during counseling to support decisions by CI candidates, CI programs, and assist manufacturers in future developments.

Electrophysiological spread of excitation and pitch perception for dual and single electrodes using the Nucleus Freedom cochlear implant.

OBJECTIVES: The first objective of the study was to determine whether there were any consistent differences in the electrophysiological spread of excitation (SOE) function, as measured using the electrically evoked compound action potential (ECAP), between dual and single electrode stimulation with the Nucleus Freedom cochlear implant system. Dual electrode stimulation is produced by electrically coupling two adjacent single electrodes. The second objective was to determine whether there were any relationships between the SOE functions and psychophysically measured pitch ranking of dual and single electrodes. DESIGN: Nine adult cochlear implant subjects participated in the study. ECAPs for dual and single electrode stimulation were measured using the forward masking paradigm, as also used in the Neural Response Telemetry (NRT) software with the Nucleus implant. Research software was used to generate the dual and single electrode stimuli and record the ECAPs. Spread of excitations (SOEs) were measured on a dual electrode and the two adjacent single electrodes, at three positions on the array: apical, mid, and basal. Compared were the ECAP amplitudes at the peak of the SOE functions, the widths of the scaled SOE functions at the 75% point, and the electrode positions at the peak of the SOE function and at the 75%, 50%, and 25% points on apical and basal sides of the scaled functions. Pitch ranking was measured for the same sets of dual and single electrodes. A two-alternative forced choice procedure was used, with the electrodes in each set paired with each other as AB and BA pairs. The subject indicated which of the two stimuli had the higher pitch. RESULTS: Dual electrode SOEs could be successfully obtained using the same methods as used to measure single electrode SOEs. The shapes of the dual and single electrodes SOEs were similar. There was a trend of a higher ECAP amplitude for the dual electrode at the peak of the SOE function, but this was only significant for two comparisons at the apical and basal positions. There were no significant differences in the SOE widths between dual and single electrodes. The electrodes at the peak of the SOE function and on the apical and basal sides of the function at the 75% position were, in most cases, tonotopically ordered. At the 50% and 25% positions, there were fewer significant differences between the dual and single electrodes The pitch ranking results showed that in 74% of cases, the single and dual electrodes at each position were successfully ranked in the expected tonotopic order. There were no statistically significant correlations between the pitch ranking results and the ordering of electrodes on the SOE functions. CONCLUSIONS: Dual electrode stimulation produced similar SOE functions as single electrode stimulation. A tonotopic ordering of electrodes at the peak of the SOE and on the sides of the functions was found, but this was not statistically related to the pitch ranking results. SUMMARY: Electrophysiological spread of neural excitation (SOE) and pitch perception using dual and single electrodes was investigated in nine subjects using the Nucleus Freedom cochlear implant. Dual electrodes are produced by electrically coupling two adjacent single electrodes. The dual and single electrodes SOEs were similar in shape. Higher electrophysiological response amplitudes were generally found for the dual electrodes. There were no differences in SOE widths between dual and single electrodes. In three quarters of cases, dual and single electrodes were successfully pitch ranked in the expected tonotopic order. No significant relationships between pitch ranking and the SOE functions were found.

Binaural speech unmasking and localization in noise with bilateral cochlear implants using envelope and fine-timing based strategies.

Four adult bilateral cochlear implant users, with good open-set sentence recognition, were tested with three different sound coding strategies for binaural speech unmasking and their ability to localize 100 and 500 Hz click trains in noise. Two of the strategies tested were envelope-based strategies that are clinically widely used. The third was a research strategy that additionally preserved fine-timing cues at low frequencies. Speech reception thresholds were determined in diotic noise for diotic and interaurally time-delayed speech using direct audio input to a bilateral research processor. Localization in noise was assessed in the free field. Overall results, for both speech and localization tests, were similar with all three strategies. None provided a binaural speech unmasking advantage due to the application of 700 micros interaural time delay to the speech signal, and localization results showed similar response patterns across strategies that were well accounted for by the use of broadband interaural level cues. The data from both experiments combined indicate that, in contrast to normal hearing, timing cues available from natural head-width delays do not offer binaural advantages with present methods of electrical stimulation, even when fine-timing cues are explicitly coded.

Results from a psychoacoustic model-based strategy for the nucleus-24 and freedom cochlear implants.

OBJECTIVE: In normal-hearing listeners acoustic masking occurs depending on frequency, amplitude, and energy of specific signals. If the selection of stimulated channels in cochlear implant systems was based on psychoacoustic masking models, the bandwidth of the electrode/nerve interface could be used more effectively by concentrating on relevant signal components and neglecting those that are usually not perceived by normal hearing listeners. Subsequently, a new strategy called PACE (Psychoacoustic Advanced Combination Encoder) has been developed which uses a psychoacoustic model for the channel selection instead of the simple maxima selection algorithm of the ACE strategy. STUDY DESIGN: Only subjects having at least 2 years experience with the ACE strategy were included. A counterbalanced cross-over design was used to compare the new speech coding strategy with the ACE strategy. SETTING: The investigation was a prospective, within-subject, repeated-measures experiment. PATIENTS: The study group consisted of 10 postlingually deafened adult subjects. INTERVENTIONS: The following programs were evaluated: (1) ACE with 8 maxima selected; (2) PACE with 8 channels selected; and (3) PACE with 4 channels selected. MAIN OUTCOME MEASURES: Speech perception tests in quiet and noise, Quality Assessment Questionnaire. RESULTS: Results indicate a trend towards better performance with PACE. Scores in the Freiburg monosyllabic word test increased by 8% while the SNR50 in the Oldenburger sentence test improved significantly by 1.3 dB. CONCLUSION: The use of psychoacoustic masking models in speech coding strategies has the potential to improve speech perception performance in cochlear implant subjects.