Deficits in auditory frequency discrimination and speech recognition in cochlear implant users

Abstract

Objectives

Speech recognition varies considerably following cochlear implantation for reasons that are still poorly understood. Considering the role of frequency discrimination in normal speech recognition, the aim of this study was to investigate the association between deficits in auditory frequency discrimination and speech recognition in cochlear implant users.

Methods

Frequency discrimination thresholds and speech recognition were assessed in a group of 20 cochlear implant users and 16 normally hearing controls.

Results

Based on their results on the speech recognition task, the cochlear implant users were categorized either as proficient (n = 10) or non-proficient users (n = 10). The non-proficient cochlear implant users had poorer auditory frequency discrimination compared to the normal hearing participants and proficient cochlear implant users (both P < 0.05). No significant difference was found between the proficient cochlear implant users and the normally hearing group (P > 0.05). Furthermore, a bivariate correlation analysis revealed a relationship between speech recognition and frequency discrimination.

Conclusions

The present findings suggest an association between auditory frequency discrimination and speech recognition proficiency in cochlear implant users. Although no causal link can be drawn from these data, possible reasons for this association are discussed.     

Fitting prelingually deafened adult cochlear implant users based on electrode discrimination performance

Objective: This study investigated the hypotheses that (1) prelingually deafened CI users do not have perfect electrode discrimination ability and (2) the deactivation of non-discriminable electrodes can improve auditory performance. Design: Electrode discrimination difference limens were determined for all electrodes of the array. The subjects’ basic map was subsequently compared to an experimental map, which contained only discriminable electrodes, with respect to speech understanding in quiet and in noise, listening effort, spectral ripple discrimination and subjective appreciation. Study Sample: Subjects were six prelingually deafened, late implanted adults using the Nucleus cochlear implant. Results: Electrode discrimination difference limens across all subjects and electrodes ranged from 0.5 to 7.125, with significantly larger limens for basal electrodes. No significant differences were found between the basic map and the experimental map on auditory tests. Subjective appreciation was found to be significantly poorer for the experimental map. Conclusions: Prelingually deafened CI users were unable to discriminate between all adjacent electrodes. There was no difference in auditory performance between the basic and experimental map. Potential factors contributing to the absence of improvement with the experimental map include the reduced number of maxima, incomplete adaptation to the new frequency allocation, and the mainly basal location of deactivated electrodes.     

Influence of stimulation rate and loudness growth on modulation detection and intensity discrimination in cochlear implant users

In cochlear implants (CIs), increasing the stimulation rate typically increases the electric dynamic range (DR), mostly by reducing audibility thresholds. While CI users’ intensity resolution has been shown to be fairly constant across stimulation rates, high rates have been shown to weaken modulation sensitivity, especially at low listening levels. In this study, modulation detection thresholds (MDTs) were measured in five CI users for a range of stimulation rates (250–2000 pulses per second) and modulation frequencies (5–100 Hz) at 8 stimulation levels that spanned the DR (loudness-balanced across stimulation rates). Intensity difference limens (IDLs) were measured for the same stimulation rates and levels used for modulation detection. For all modulation frequencies, modulation sensitivity was generally poorer at low levels and at higher stimulation rates. CI users were sensitive to modulation frequency only at relatively high levels. Similarly, IDLs were poorer at low levels and at high stimulation rates. When compared directly in terms of relative amplitude, IDLs were generally better than MDTs at low levels. Differences in loudness growth between dynamic and steady stimuli might explain level-dependent differences between MDTs and IDLs. The slower loudness growth associated with high stimulation rates might explain the poorer MDTs and IDLs with high rates. In general, high stimulation rates provided no advantage in intensity resolution and a disadvantage in modulation sensitivity.     

Contribution of hearing aids to music perception by cochlear implant users

Abstract

Objectives

Modern cochlear implant (CI) encoding strategies represent the temporal envelope of sounds well but provide limited spectral information. This deficit in spectral information has been implicated as a contributing factor to difficulty with speech perception in noisy conditions, discriminating between talkers and melody recognition. One way to supplement spectral information for CI users is by fitting a hearing aid (HA) to the non-implanted ear.

Methods

In this study 14 postlingually deaf adults (half with a unilateral CI and the other half with a CI and an HA (CI + HA)) were tested on measures of music perception and familiar melody recognition.

Results

CI + HA listeners performed significantly better than CI-only listeners on all pitch-based music perception tasks. The CI + HA group did not perform significantly better than the CI-only group in the two tasks that relied on duration cues. Recognition of familiar melodies was significantly enhanced for the group wearing an HA in addition to their CI. This advantage in melody recognition was increased when melodic sequences were presented with the addition of harmony.

Conclusion

These results show that, for CI recipients with aidable hearing in the non-implanted ear, using a HA in addition to their implant improves perception of musical pitch and recognition of real-world melodies.     

Channel discrimination along all contacts of the cochlear implant electrode array and its relation to speech perception

Objective: To test the channel discrimination of cochlear implant (CI) users along all contacts of the electrode array and assess whether this is related to speech perception.

Design: CI recipients were tested with a custom-made channel discrimination test. They were asked to distinguish a target stimulus from two reference stimuli in a three-alternative forced choice (3AFC) task. The target stimulus was evoked using current steering, with current steering coefficients (α) of 1, 0.5 and 0.25. The test provided a discrimination score (Dα) for each electrode contact along the array.

Study sample: Thirty adults implanted with a CI from Advanced Bionics.

Results: Large variations in Dα scores were observed, both across the electrode array and between subjects. Statistical analysis revealed a significant channel-to-channel variability in Dα score (p?p?Conclusions: The large variations in Dα score emphasise the importance of testing pitch discrimination across the complete electrode array. The relationship between Dα score and speech perception indicates that pitch discrimination might be a contributing factor to the performance of individual implant users.     

Audiovisual speech perception in elderly cochlear implant recipients

OBJECTIVES/HYPOTHESIS: This study examined the speech perception skills of a younger and older group of cochlear implant recipients to determine the benefit that auditory and visual information provides for speech understanding. STUDY DESIGN: Retrospective review. METHODS: Pre- and postimplantation speech perception scores from the Consonant-Nucleus-Consonant (CNC), the Hearing In Noise sentence Test (HINT), and the City University of New York (CUNY) tests were analyzed for 34 postlingually deafened adult cochlear implant recipients. Half were elderly (i.e., >65 y old) and other half were middle aged (i.e., 39-53 y old). The CNC and HINT tests were administered using auditory-only presentation; the CUNY test was administered using auditory-only, vision-only, and audiovisual presentation conditions RESULTS: No differences were observed between the two age groups on the CNC and HINT tests. For a subset of individuals tested with the CUNY sentences, we found that the preimplantation speechreading scores of the younger group correlated negatively with auditory-only postimplant performance. Additionally, older individuals demonstrated a greater reliance on the integration of auditory and visual information to understand sentences than did the younger group CONCLUSIONS: On average, the auditory-only speech perception performance of older cochlear implant recipients was similar to the performance of younger adults. However, variability in speech perception abilities was observed within and between both age groups. Differences in speechreading skills between the younger and older individuals suggest that visual speech information is processed in a different manner for elderly individuals than it is for younger adult cochlear implant recipients.     

Long-term performance of Clarion 1.0 cochlear implant users

OBJECTIVE/HYPOTHESIS: To evaluate the long-term performance of adult Clarion 1.0 cochlear implant users. STUDY DESIGN: This was a retrospective, longitudinal study evaluating word discrimination in quiet for 31 adult cochlear implant patients with preimplantation sentence scores of less than 10%. METHODS: The length of the study was 135 months with a mean follow-up length of 93 (median, 96) months. For the duration of the study, all subjects used the Clarion 1.0 cochlear implant with speech processors programmed for the use of the continuous interleaved sampling strategy. RESULTS: There was no significant growth or decline in speech perception after 24 months postimplantation unless adverse medical events were experienced. Age at implantation was significantly and substantially negatively correlated (-11% word score per decade, r = 0.68) with most recent score, maximum score, time to maximum score, range of performance, 24- to 130-month mean score, and for any longitudinal data point tested: 3 to 6 months, 6 months, 1 year, 2 years, 5 years, and 10 years. There were no age-related declines in performance. There were no observed correlations between duration of deafness and any of the variables listed above. CONCLUSIONS: The lack of correlation between duration of deafness and performance in a cohort without residual hearing suggests the presence of a strong correlation between age and speech performance with a cochlear implant. That the cochlear implant is a safe therapy for the treatment of profound deafness is supported by the stability of scores through the 10-year study period as well as a zero rate of device failures or explantation.     

Effect of input compression and input frequency response on music perception in cochlear implant users

Objective: A study was conducted to determine whether modifications to input compression and input frequency response characteristics can improve music-listening satisfaction in cochlear implant users. Design: Experiment 1 compared three pre-processed versions of music and speech stimuli in a laboratory setting: original, compressed, and flattened frequency response. Music excerpts comprised three music genres (classical, country, and jazz), and a running speech excerpt was compared. Experiment 2 implemented a flattened input frequency response in the speech processor program. In a take-home trial, participants compared unaltered and flattened frequency responses. Study sample: Ten and twelve adult Nucleus Freedom cochlear implant users participated in Experiments 1 and 2, respectively. Results: Experiment 1 revealed a significant preference for music stimuli with a flattened frequency response compared to both original and compressed stimuli, whereas there was a significant preference for the original (rising) frequency response for speech stimuli. Experiment 2 revealed no significant mean preference for the flattened frequency response, with 9 of 11 subjects preferring the rising frequency response. Conclusions: Input compression did not alter music enjoyment. Comparison of the two experiments indicated that individual frequency response preferences may depend on the genre or familiarity, and particularly whether the music contained lyrics.     

Nucleus24M型人工耳蜗植入后电极阻抗的变化

目的：研究人工耳蜗植入后电极阻抗的变化规律，以便确定术后进行映射调图的时间表。方法：对16例植入Nucleus CI24M型人工耳蜗患者，于术中及术后1、1．5、2、4、6个月进行电极阻抗测试，统计分析电极阻抗的变化规律。结果：患者电极阻抗在术中检测时最低，开机时最高，以后若干次随访时，阻抗逐渐下降，并在2～4个月左右趋于稳定。结论：电极阻抗的稳定提示耳蜗内生物组织的病理过程渐趋稳定；对心理物理测试配合良好的患者，术后只进行2～4个月左右的映射调图即可。     

The long-term results of speech perception in elderly cochlear implant users

Objectives: To evaluate the speech discrimination performance of elderly post-lingually deafened cochlear implant (CI) users and the stability of performance over time relative to a control group of younger CI users.

Methods: The study group consisted of 20 native Dutch speaking, post-lingually deafened CI users, aged 70 or older at the time of implantation. Controls were patients aged 40–60 years at implantation and included according to the same inclusion criteria (except age). Linear mixed models assessed speech recognition scores between groups, the variability of their performance, and stability over time.

Results: 20 elderly and 37 controls were included. The mean follow-up was 4.4 and 5.3 years for elderly and controls, respectively. There was no significant difference in average speech discrimination between both groups. The elderly group had a larger intra-subject variability over time. There was no significant effect of follow-up on the speech discrimination, indicating a stable performance over time.

Discussion: This study has a longer follow-up than methodologically comparable previous studies. We found no difference in speech discrimination between elderly patients and controls and no deterioration of performance over time. The subjects in the elderly group exhibit a larger variability around their mean performance.

Conclusion: Speech recognition in both elderly and younger adult CI users is stable over time and is not significantly related to the age of implantation.     

Patients' involvement in choosing a cochlear implant

Abstract

Objective

The study describes the procedure followed by the South of England Cochlear Implant Centre, Southampton in involving the patients in their choice of device and it also describes the reasons given by patients for choosing a particular device.

Methods

A retrospective service evaluation of 43 adults and 19 children was carried out and the data was analysed.

Results

A wide range of reasons for choosing a particular device were reported. However, it is notable that the single most common reason for choosing a particular device was related to the aesthetics.

Discussion

The data suggest that the main reason for choosing a particular device related more to the aesthetics and comfort of the device irrespective of the technical aspects.     

Perception of speech by prelingual pre-adolescent and adolescent cochlear implant users

Abstract

This study was undertaken to assess the speech perception benefits, 24 months after cochlear implantation (CI), in 20 young people (age at CI, 8–18.5 years) with prelingual profound hearing loss, in addition to the use of a proposed CI candidacy assessment profile. Speech perception was evaluated in terms of word and sentence perception before CI, and at six-monthly intervals for two years after CI. Before undergoing CI, all participants were tested on a pre-implantation assessment profile. Compared to the pre-CI findings, group results over 24 months post-CI demonstrated improved speech perception abilities reaching, on average, 46% for word recognition, 71.3% for sentences in quiet, and 33.6% for sentences in noise. Pre-CI profile scores correlated significantly with all speech perception results obtained 24 months after CI. Thus, despite their relatively late ages at implantation, all participants showed gradually improving performance in speech perception. The results showed a high variability in the outcomes of the participants. The pre-CI profile appeared to be useful in formulating realistic expectations of CI outcome during pre-implantation consultations, suggesting that expectations can and should be managed according to each patient's pre-implantation assessment.

Sumario

Se llevó a cabo este estudio para evaluar los beneficios en la percepción del lenguaje, 24 meses después de la implant-ación coclear (CI), en 20 personas jóvenes (edad en la CI de 8-18.5 años), con sordera prelingüística profunda, en quienes se usó un perfil propuesto de evaluación para la candidatura a la CI. La percepción del lenguaje se evaluó en términos de percepción de palabras y oraciones antes de la CI y a intervalos de seis meses, durante dos años, después de la CI. Antes de la CI todos los participantes fueron examinados con un perfil de evaluación pre-implantación. Comparados con los hallazgos pre-CI, los resultados del grupo después de 24 meses de la CI mostraron mejoría en las habilidades para la percepción del lenguaje alcanzando, en promedio, 46% para el reconocimiento de palabras, 71.3% para oraciones sin ruido y 33.6% para oraciones con ruido. Las puntuaciones en el perfil pre-CI correlacionaron significativamente con todos los resultados de percepción del lenguaje obtenidos 24 meses después de la CI. Así, a pesar de las edades de implantación relativamente tardías, todos los participantes mostraron un desempeño gradual-mente mejor en la percepción del lenguaje. Los resultados mostraron una gran variabilidad en los resultados de los participantes. El Perfil pre-CI parece ser útil para formular expectativas realistas sobre los resultados de la CI durante las consultas pre-implante, sugiriendo que las expectativas pueden y deben ser manejadas de acuerdo con las evaluaciones pre-implantación de cada paciente.     

Effect of preoperative residual hearing on speech perception after cochlear implantation

Objective: To assess the effect of substantial preoperative residual hearing on speech perception outcomes in adult cochlear implant recipients. Setting: Tertiary care academic referral center. Methods: Twenty‐nine patients with substantial preoperative residual hearing underwent cochlear implantation. Twenty‐one implant recipients matched for age and duration of hearing loss, but without preoperative residual hearing, served as controls. Postoperative speech perception was assessed using City University of New York sentence, consonant‐nucleus‐consonant, and hearing in noise test in quiet and in noise (+10 dB signal to noise ratio) tests at 1, 3, 6, and 12 months after fitting. Results: After implantation, there were no significant differences between groups for any of the tests administered. The mean change in speech perception abilities from baseline was significantly greater for the control patients than those with substantial preoperative residual hearing at a number of the test intervals across the various conditions. Moreover, at both 1 and 3 months, some patients in the residual hearing group had speech perception scores that were worse than their preoperative values. Ultimately, all of the patients with substantial residual hearing surpassed their preoperative performance. Discussion: Patients with substantial preoperative residual hearing can gain significant benefit from cochlear implantation. Although the degree of improvement in these individuals is somewhat more modest than for those patients without preoperative residual hearing, the outcomes are still excellent. That there were no significant differences between the patient groups suggests that having substantial residual hearing before implantation does not provide a measurable performance advantage for electrical stimulation. Patients with substantial residual hearing who are contemplating cochlear implantation should be counseled regarding a possible initial decline in speech perception performance.     

汉语普通话人工耳蜗使用者对声调识别的分析研究

目的 初步确定人工耳蜗使用者声调感知的特点,并进行分析研究.方法 利用自主开发的噪声下声调识别测试材料(tone identification in noise test,TINT)在Speech Performance测试平台的控制下对20例母语为汉语普通话人工耳蜗使用者声调识别能力进行评估,获得各声调识别成绩以及声调识别混淆矩阵.采用χ2检验(chi-square test)对本组人工耳蜗使用者汉语声调识别成绩差异进行统计学分析.结果 ①本组人工耳蜗使用者的汉语普通话声调识别总成绩(百分制得分)分布48.75%~98.75%,平均成绩(76.38±17.29)%;②各声识别成绩平均值差异显著(χ2=2358.357,P<0.01),由高到低分别为T3(85.75%)>T4(85.25%)>T1(69.75%)>T2(64.75%),即本组人工耳蜗植入者感知T3、T4较为容易、感知T1、T2较为困难;③声调识别混淆矩阵提示T2(35.35%)、T1(30.25%)混淆度明显高于T4(14.75%)、T3(14.25%),并且各个声调之间的混淆趋势不同,T1易被混淆为T2(18.25%)、T2易被混淆为T3(24.00%).结论 时域特性明显的声调更易被人工耳蜗群体识别,因此应根据声调感知难易程度制定针对性的声调康复训练方案,综合利用听觉信息和视觉信息改善声调,特别是一声、二声的识别能力.     

The role of intensity upon pitch perception in cochlear implant recipients

OBJECTIVES: Pitch plays a key role in the perception of speech and music, the recognition of a speaker's voice, and in analyzing complex auditory patterns. To date, little consideration has been given to the influence of stimulation level on pitch perception. The aim of this study was to investigate the impact of a sound's intensity on pitch perception in cochlear implant recipients using monopolar stimulation. STUDY DESIGN: Thirteen patients with an average implant use of 4.13 years took part in this study. All patients were implanted with MedEl Combi 40/40+ cochlear implants. METHODS: In the first part of the study, we performed a pitch ranking procedure to confirm that all patients were able to judge pitch changes. Using a visual scale, study participants were then asked to compare the pitch of an intensity-constant reference tone with the pitch of a test tone of varying intensity. RESULTS: Eleven (85%) patients were found to perceive a clear change in pitch with changing stimulus intensity. Statistical analysis showed a strong positive correlation in 10 patients (correlation coefficients between 0.99 and 0.71) and a strong negative correlation in 1 patient (r = -0.92). CONCLUSIONS: The results suggest that a distinct relationship exists between pitch perception and intensity of the stimulus. To date, speech coding strategies do not support these findings. Nevertheless, we believe that for the optimized most natural perception of sounds, especially music, the described particularities of pitch perception need to be respected, and further investigations on this topic are necessary.     

Simultaneous communication supports learning in noise by cochlear implant users

Objectives: This study sought to evaluate the potential of using spoken language and signing together (simultaneous communication, SimCom, sign-supported speech) as a means of improving speech recognition, comprehension, and learning by cochlear implant (CI) users in noisy contexts.

Methods: Forty eight college students who were active CI users, watched videos of three short presentations, the text versions of which were standardized at the 8^th-grade reading level. One passage was presented in spoken language only, one was presented in spoken language with multi-talker babble background noise, and one was presented via simultaneous communication with the same background noise. Following each passage, participants responded to 10 (standardized) open-ended questions designed to assess comprehension. Indicators of participants’ spoken language and sign language skills were obtained via self-reports and objective assessments.

Results: When spoken materials were accompanied by signs, scores were significantly higher than when materials were spoken in noise without signs. Participants’ receptive spoken language skills significantly predicted scores in all three conditions; neither their receptive sign skills nor age of implantation predicted performance.

Discussion: Students who are CI users typically rely solely on spoken language in the classroom. The present results, however, suggest that there are potential benefits of simultaneous communication for such learners in noisy settings. For those CI users who know sign language, the redundancy of speech and signs potentially can offset the reduced fidelity of spoken language in noise.

Conclusion: Accompanying spoken language with signs can benefit learners who are CI users in noisy situations such as classroom settings. Factors associated with such benefits, such as receptive skills in signed and spoken modalities, classroom acoustics, and material difficulty need to be empirically examined.     

人工耳蜗植入患者对西洋乐器和民族乐器感知研究

目的分析人工耳蜗植入患者对西洋乐器和我国民族乐器感知能力的差异,探讨人工耳蜗植入者与听力正常者在音乐音色感知的规律特征和听配能差异。方法耳蜗组和对照组受试者各20例,使用音乐感知评估平台对两组受试者进行音色识别能力测试,记录并比较两组音色识别正确率和总应答反应时间。结果①耳蜗组音色识别正确率（80.42±11.87）%,显著低于对照组正确率（96.67±4.19）%,差异具有统计学意义（P＜0.01）。②耳蜗组对我国民族乐器（琵琶、二胡）识别正确率82.50%,西洋乐器正确率80.00%,两者差异无统计学意义（P=0.664）。③耳蜗组对音色测试总应答反应时间（170.50±21.81）s,与对照组（161.85±18.18）s比较,差异无统计学意义（t=1.363,P＞0.05）。结论人工耳蜗植入患者对音乐音色的感知能力显著低于听力正常者,在测听任务过程中所需听配能增加,并且容易混淆管弦乐器。对比西洋乐器,人工耳蜗植入患者对我国民族乐器的感知无明显优势。     

Mandarin Chinese speech recognition by pediatric cochlear implant users

Objectives

Because of difficulties associated with pediatric speech testing, most pediatric cochlear implant (CI) speech studies necessarily involve basic and simple perceptual tasks. There are relatively few studies regarding Mandarin-speaking pediatric CI users’ perception of more difficult speech materials (e.g., words and sentences produced by multiple talkers). Difficult speech materials and tests necessarily require older pediatric CI users, who may have different etiologies of hearing loss, duration of deafness, CI experience. The present study investigated how pediatric CI patient demographics influence speech recognition performance with relatively difficult test materials and methods.

Methods

In this study, open-set recognition of multi-talker (two males and two females) Mandarin Chinese disyllables and sentences were measured in 37 Mandarin-speaking pediatric CI users. Subjects were grouped according to etiology of deafness and previous acoustic hearing experience. Group 1 subjects were all congenitally deafened with little-to-no acoustic hearing experience. Group 2 subjects were not congenitally deafened and had substantial acoustic hearing experience prior to implantation. Multiple linear regression analyses were performed within each group using subject demographics such as age at implantation and age at testing.

Results

Pediatric CI performance was generally quite good. For Group 1, mean performance was 82.3% correct for disyllables and 82.8% correct for sentences. For Group 2, mean performance was 76.6% correct for disyllables and 84.4% correct for sentences. For Group 1, multiple linear regression analyses showed that age at implantation predicted disyllable recognition, and that age at implantation and age at testing predicted sentence recognition. For Group 2, neither age at implantation nor age at testing predicted disyllable or sentence recognition. Performance was significantly better with the female than with the male talkers.

Conclusions

Consistent with previous studies’ findings, early implantation provided a significant advantage for profoundly deaf children. Performance for both groups was generally quite good for the relatively difficult materials and tasks, suggesting that open-set word and sentence recognition may be useful in evaluating speech performance with older pediatric CI users. Differences in disyllable recognition between Groups 1 and 2 may reflect differences in adaptation to electric stimulation. The Group 1 subjects developed speech patterns exclusively via electric stimulation, while the Group 2 subjects adapted to electric stimulation relative to previous acoustic patterns.