Comparison of EAP thresholds with MAP levels in the nucleus 24 cochlear implant: data from children

OBJECTIVE: The purpose of this study is to examine the relationship between the electrically evoked compound action potential (EAP) thresholds and the MAP thresholds (T-levels) and maximum comfort levels (C-levels) in children implanted with the Nucleus 24 device. DESIGN: EAP thresholds were measured using the Neural Response Telemetry system of the Nucleus 24 device. Twenty children implanted with the Nucleus 24 cochlear implant participated in this study. EAP thresholds were compared with the behavioral measures of T- and C-level used to construct the MAP these children used on a daily basis. For these subjects, both EAP and MAP T- and C-levels were obtained the same visit, which occurred at 3 to 5 mo postconnection. RESULTS: EAP thresholds were shown to fall between MAP T- and C-level for 18 of 20 subjects tested; however, considerable variability across subjects was noted. On average, EAP thresholds fell at 53% of the MAP dynamic range. Correlations between EAP threshold and MAP T- and C-level improved substantially when combined with behavioral measures obtained from one electrode in the array. CONCLUSIONS: Moderate correlations were found between EAP thresholds and MAP T- and C-levels for the children participating in this study. However, a technique is described for improving the accuracy of predictions of MAP T- and C-levels based on EAP data combined with a small amount of behavioral information.     

Comparison of speech perception performance between the nucleus 24 and nucleus 24 contour cochlear implant systems

Objective—To compare the 1-, 3-, and 6-month postoperative speech perception scores obtained by a group of subjects who received the new perimodiolar array (Nucleus Contour) cochlear implant with those obtained by a group of subjects implanted with the straight electrodes of the previous-generation Nucleus 24 device.

Material and Methods—The speech performance of 10 postlingually deafened adults implanted with the Nucleus Contour device was compared with that of matched controls who received the Nucleus 24 model. Objective measures included word and sentence speech recognition scores.

Results—Patients implanted with the Nucleus Contour device obtained significantly higher word and sentence recognition scores after short-term use of the implant compared to those obtained by patients implanted with the Nucleus 24 model.

Conclusion—Further long-term studies are required to determine whether the Nucleus Contour CI recipients continue to improve over time.     

Cochlear implants: 100 pediatric case conversions from the body worn to the nucleus esprit 22 ear level speech processor.

OBJECTIVE: To assess performance of Nucleus 22 mini system pediatric users converted from the Spectra 22 body-worn to the ESPrit 22 ear-level speech processor using aided thresholds and speech discrimination measures before and after the conversion. STUDY DESIGN: Spectra 22 body-worn speech processor users were chosen using preselection criteria (stable map, ability to report on the quality of the signal, no device problems). The subjects underwent tuning, map conversion, fitting of the ESPrit 22, and aided soundfield threshold and speech discrimination testing. SUBJECTS: The first 100 consecutive conversions are analyzed in this study. Fifty children (50%) were female, and 50 (50%) were male. The average age at implantation was 4.6 years (median 4.3 years, range 1.7 to 11 years). The average age of fitting the ear level speech processor was 11.1 years (median 11 years, range 6.2 to 18.2 years). SETTING: Tertiary referral pediatric cochlear implant center in the United Kingdom. RESULTS: Of the 100 fittings attempted, all Spectra 22 maps could to be converted for use in the ESPrit 22. Of these 100 fittings, 44 were straightforward with no adjustment to map parameters being required, and 56 needed rate reductions and other map adjustments to achieve the conversion. The difference of the mean thresholds before and after the conversion did not exceed 2 dB across the frequencies studied (0.5-4 kHz). In 95% of the cases, the differences were less than 9 dB(A). With regard to speech discrimination testing, the mean threshold before the conversion was 53.4 dB and after the conversion 52.7 dB. Of the 100 conversions, only five children stopped using the ESPrit 22 despite fitting being achieved. CONCLUSION: Conversion from the Spectra 22 body worn to the ESPrit 22 ear level speech processor was found to be feasible in all the 100 cases studied. Only a minority (5%) of children chose not to use the ear level speech processor suggesting that children and parents were satisfied from the conversion.     

Click声诱发脑干检测反应阈与行为听阈相关性报告

目的了解听觉脑干诱发电位（ABR）阈值与行为测听阈值之间的相关性,探讨受试者的听力损失程度和频率间的差异对两类测试结果相关性的影响。结合回顾性分析法,对大量样本进行统计分析,试提出一组合理高效的临床声诱发听力检测测试链,以期可准确、快速的获取受试者的听阈,为无法配合听力测试或行为测试结果不可靠的听障儿童的早期听力干预、助听器验配及调试提供可靠的依据。方法对117例（233耳）感音神经性聋患儿分别进行ABR测试及行为测听,记录相应的测试结果进行统计和比较。结果ABR反应阈值较行为测听阈值普遍偏高,且随着受试者听力损失的加重,两者之间的差距逐步缩小;在刺激信号频率为0.5、1.0、2.0和4.0kHz时（包括平均听力）,受试者的ABR反应阈值和行为测听阈值的相关系数分别为0.5591、0.6655、0.7075、0.5675和0.7245,具有显著的相关性（P〈0.01）;同时当受试者的ABR反应阈值处于90dBnHL～100dBnHL之间时,其ABR的反应阈值与行为听阈十分接近,当受试者的ABR反应阈值〉100dBnHL时,其0.5和1kHz处的行为听阈在100～110dB之间,2.0和4.0kHz处的行为听阈在110dB以上。结论ABR反应阈值可较准确的预测听障儿童的听力情况,为无法配合听力测试或行为测试结果不可靠的听障儿童的早期听力干预、助听器验配及调试提供可靠的依据,但建议在Click-ABR的基础上结合Tone-ABR的0.5和1.0kHz用以完整受试者的听力图。     

Frequency-specific auditory brainstem responses. Effective masking levels and relationship to behavioural thresholds in normal hearing adults

Ipsilateral masking levels and normal thresholds for tone pip auditory brainstem responses (ABRs) were investigated in normal subjects for the purpose of establishing recording parameters and norms for frequency-specific tone pip ABR testing. White noise was found to effectively mask ABRs to tone pips at mean signal-to-noise ratios of between -1 and -5.5 dB [dB peak-equivalent (pe) SPL/dB SPL] depending on the tone pip frequency. ABR thresholds were established for tone pips in the presence of ipsilateral masking with high-pass filtered noise for 50-Hz tone pips and notched noise for tone pips from 1,000 to 4,000 Hz, at a nominal signal-to-noise ratio of -5 dB (i.e. with the noise SPL measured prior to filtering). Thresholds occurred between 28.6 and 36.6 dB pe SPL, equivalent to 4.4-8.8 dB nHL. ABR thresholds for masked and unmasked tone pips did not differ significantly.     

A comparison of the growth of open-set speech perception between the nucleus 22 and nucleus 24 cochlear implant systems.

OBJECTIVE: To compare the short-term development of open-set speech perception between implementations of the spectral peak (SPEAK) strategy in adults using the Nucleus 22 (N22) Spectra processor and the Nucleus 24 (N24) system with the SPrint processor. STUDY DESIGN: Two sets of patients with a follow-up period of 3 months were compared. SETTING: This study was conducted at the New York University (NYU) Medical Center. PATIENTS: Thirty-six profoundly hearing-impaired adults were included in this study. INTERVENTION: Sixteen adults received the N22 cochlear implant with the Spectra speech processor and twenty adults received the N24 cochlear implant with the SPrint speech processor. MAIN OUTCOME MEASURES: Open-set speech perception for the patients with N22 implants was evaluated preoperatively and postoperatively using the following measures: NU-6 monosyllabic words, Iowa sentences, and CID sentences. CNC words, CUNY sentences, and HINT sentences were used to assess the patients with N24 implants. RESULTS: Results revealed that the N22 and N24 cochlear implant recipients had significant open-set speech recognition 3 and 6 months after implantation. The apparent favorable absolute scores for the patients with N24 implants were equalized when a multivariate analysis was performed to account for their younger age at time of implantation and shorter length of deafness. CONCLUSIONS: The growth of open-set word and sentence recognition in similar between the N22 and N24 cochlear implants. Longitudinal studies are needed to determine if higher ceiling scores are present in the N24. Further exploration of monopolar versus bipolar stimulation is warranted.     

Speech recognition with the nucleus 24 SPEAK,ACE, and CIS speech coding strategies in newly implanted adults

OBJECTIVE: The objective of this study was to determine whether 1) the SPEAK, ACE or CIS speech coding strategy was associated with significantly better speech recognition for individual subjects implanted with the Nucleus CI24M internal device who used the SPrint speech processor, and 2) whether a subject's preferred strategy for use in everyday life provided the best speech recognition. DESIGN: Twelve postlinguistically deaf, newly implanted adults participated. Initial preference for the three strategies was obtained with paired-comparison testing on the first day of implant stimulation with seven of eight U.S. subjects. During the first 12 wk, all subjects used each strategy alone for 4 wk to give them experience with the strategy and to identify preferred speech processor program parameters and settings that would be used in subsequent testing. For the next 6 wk, subjects used one strategy at a time for 2-wk intervals in the same order they had for the first 12 wk. At the end of each 2-wk interval, speech recognition testing was conducted with all three strategies. At the end of the 6 wk, all three strategies were placed on each subject's processor, and subjects were asked to compare listening with these three programs in as many situations as possible for the next 2 wk. When they returned, subjects responded to a questionnaire asking about their preferred strategy and responded to two lists of medial consonants using each of the three strategies. The U.S. subjects also responded to two lists of medial vowels with the three strategies. RESULTS: Six of the 12 subjects in the present study had significantly higher CUNY sentence scores with the ACE strategy than with one or both of the other strategies; one of the 12 subjects had a significantly higher score with SPEAK than with ACE. In contrast, only two subjects had significantly higher CNC word and phoneme scores with one or two strategies than with the third strategy. One subject had a significantly higher vowel score with the SPEAK strategy than with the CIS strategy; and no subjects had significantly higher consonant scores with any strategy. Seven of 12 subjects preferred the ACE strategy, three preferred the SPEAK strategy, and two preferred the CIS strategy. Subjects' responses on a questionnaire agreed closely with strategy preference from comparisons made in everyday life. There was a strong relation between the preferred strategy and scores on CUNY sentences but not for the other speech tests. For all subjects, except one, the preferred strategy was the one with the highest CUNY sentence score or was a strategy with a CUNY score not significantly lower than the highest score. CONCLUSIONS: Despite differences in research design, there was remarkably close agreement in the pattern of group mean scores for the three strategies for CNC words and CUNY sentences in noise between the present study and the Conversion study (Arndt, Staller, Arcaroli, Hines, & Ebinger, Reference Note 1). In addition, essentially the same percentage of subjects preferred each strategy. For both studies, the strategy with which subjects had the highest score on the CUNY sentences in noise evaluation was strongly related to the preferred strategy; this relation was not strong for CNC words, CNC phonemes, vowels or consonants (Skinner, Arndt, & Staller, 2002). These results must be considered within the following context. For each strategy, programming parameters preferred for use in everyday life were determined before speech recognition was evaluated. In addition, implant recipients had experience listening with all three strategies in many situations in everyday life before choosing a preferred strategy. Finally, 11 of the 12 subjects strongly preferred one of the three strategies. Given the results and research design, it is recommended that clinicians fit each strategy sequentially starting with the ACE strategy so that the preferred programming parameters are determined for each strategy before recipients compare pairs of strategies. The goal is to provide the best opportunity for individuals to hear in everyday life within a clinically acceptable time period (e.g., 6 wk).     

Cochlear implants in young children: the relationship between speech perception and speech intelligibility.

OBJECTIVE: To determine the relationship between measures of speech perception and speech production after cochlear implantation of young children with profound congenital and prelingual deafness. DESIGN: A prospective study was undertaken on a consecutive group of children with profound deafness. There were 126 children at the preimplantation interval and 71, 50, 26, and 20 children, respectively, at the 2, 3, 4, and 5 yr follow-up after implantation. Speech perception and speech intelligibility were assessed using hierarchical rating scales. Spearman rank correlation coefficients were used to determine the statistical correlations. All patients were either congenitally deaf or deafened before the age of 3 yr and were implanted before age 7 yr. The patients all received the Nucleus multichannel cochlear implant system with the most appropriate speech encoding strategy. RESULTS: Speech intelligibility at 5 yr was strongly correlated with speech perception at the 2, 3, 4, and 5 yr intervals after implantation (Spearman coefficients 0.77, 0.81, 0.58, 0.58; p < or = 0.01). Speech intelligibility at the 2, 3, and 4 yr intervals also correlated in a similar manner with earlier speech perception abilities (p < or = 0.01). CONCLUSIONS: The results suggest that speech intelligibility between 2 and 5 yr after implantation in young children with congenital and prelingual profound deafness can be predicted by measures of earlier speech perception.     

An investigation of input level range for the nucleus 24 cochlear implant system: speech perception performance,program preference,and loudness comfort ratings

OBJECTIVE: Cochlear implant recipients often have limited access to lower level speech sounds. In this study we evaluated the effects of varying the input range characteristics of the Nucleus 24 cochlear implant system on recognition of vowels, consonants, and sentences in noise and on listening in everyday life. DESIGN: Twelve subjects participated in the study that was divided into two parts. In Part 1 subjects used speech processor (Nucleus 24 SPrint trade mark ) programs adjusted for three input sensitivity settings: a standard or default microphone sensitivity setting (MS 8), a setting that increased the input sensitivity by 10.5 dB (MS 15), and the same setting that increased input sensitivity but also incorporated the automatic sensitivity control (ASC; i.e., MS 15A) that is designed to reduce the loudness of noise. The default instantaneous input dynamic range (IIDR) of 30 dB was used in these programs (i.e., base level of 4; BL 4). Subjects were tested using each sensitivity program with vowels and consonants presented at very low to casual conversational levels of 40 dB SPL and 55 dB SPL, respectively. They were also tested with sentences presented at a raised level of 65 dB SPL in multi-talker babble at individually determined signal to noise ratios. In addition, subjects were given experience outside of the laboratory for several weeks. They were asked to complete a questionnaire where they compared the programs in different listening situations as well as the loudness of environmental sounds, and state the setting they preferred overall.In Part 2 of the study, subjects used two programs. The first program was their preferred sensitivity program from Part 1 that had an IIDR of 30 dB (BL 4). Seven subjects used MS 8 and four used MS 15, and one used the noise reduction program MS 15A. The second program used the same microphone sensitivity but had the IIDR extended by an additional 8 to 10 dB (BL 1/0). These two programs were evaluated similarly in the speech laboratory and with take-home experience as in Part 1. RESULTS PART 1: Increasing the microphone input sensitivity by 10.5 dB (from MS 8 to MS 15) significantly improved the perception of vowels and consonants at 40 and 55 dB SPL. The group mean improvement in vowel scores was 25 percentage points at 40 dB SPL and 4 percentage points at 55 dB SPL. The group mean improvement for consonants was 23 percentage points at 40 dB SPL and 11 percentage points at 55 dB SPL. Increased input sensitivity did not significantly reduce the perception of sentences presented at 65 dB SPL in babble despite the fact that speech peaks were then within the compressed range above the SPrint processor's automatic gain control (AGC) knee-point.Although there was a demonstrable advantage for perception of low-level speech with the higher input sensitivity (MS 15 and 15A), seven of the 12 subjects preferred MS 8, four preferred MS 15 or 15A, and one had no preference overall. Approximately half the subjects preferred MS 8 across the 18 listening situations, whereas an average of two subjects preferred MS 15 or 15A. The increased microphone sensitivity of MS 15 substantially increased the loudness of environmental sounds. However, use of the ASC noise reduction setting with MS 15 reduced the loudness of environmental sounds to equal or below that for MS 8. RESULTS PART 2: The increased instantaneous input range gave some improvement (8 to 9 percentage points for the 40 dB SPL presentation level) in the perception of consonants. There was no statistically significant increase in vowel scores. Mean scores for sentences presented at 65 dB SPL in babble were significantly lower (5 percentage points) for the increased IIDR setting. Subjects had no preference for the increased IIDR over the default. The IIDR setting had no effect on the loudness of environmental sounds. CONCLUSIONS: Given the fact that individuals differ in threshold (T) and comfort (C) levels for electrical stimulation, and preferred microphone sensitivity, volume control, and noise-reduction settings, it is essential for the clinicid recipient to determine what combination is best for the individual over several sessions.The results of this study clearly show the advantage of using higher microphone sensitivity settings than the default MS 8 to provide better speech recognition for low-level stimuli. However, it was also necessary to adjust other parameters such as map C levels, automatic sensitivity control and base level, to optimize loudness comfort in the diversity of listening situations an individual encounters in everyday life.     

The relationship between the intraoperative ECAP threshold and postoperative behavioral levels: the difference between postlingually deafened adults and prelingually deafened pediatric cochlear implant users

The purpose of this study was to determine the relationship between electrically evoked compound-action potential (ECAP) thresholds, electrically evoked auditory brain-stem response (EABR) thresholds, behavioral thresholds (T levels) and maximum comfort levels (C levels) in profoundly deaf cochlear-implant users. The ECAP thresholds were measured intraoperatively in eight postlingually deafened adults and nine (eight prelingually and one postlingually deafened) children implanted with the Nucleus CI24 M cochlear implant. The mean ECAP thresholds did not differ between children and adults. The average behavioral T and C levels after at least 6 months of experience with a cochlear implant were significantly higher in children than those in adults. The ECAP thresholds were more strongly correlated with T and C levels in children than in adults. The stronger correlation between ECAP thresholds and behavioral T and C levels in children than in adults might result from differences in loudness sensation, which should in turn depend on auditory experience.     

Unmasked thresholds and minimum masking in infants and adults: separating sensory from nonsensory contributions to infant-adult differences in behavioral thresholds

OBJECTIVE: The purposes were to determine the degree to which infant unmasked thresholds differed from those of adults, to determine the effect of signal frequency on those differences, and to determine whether there is a difference in minimum effective masking as a function of age and frequency. The data were applied to a model to address the question of the origin (sensory versus nonsensory) of infant-adult differences in behavioral unmasked thresholds. DESIGN: Infant behavioral thresholds in quiet and in noise for pure tones of 0.5 and 2 kHz were measured using computer-based visual reinforcement audiometry. Adult thresholds were measured using the same apparatus and a modified conventional audiometric procedure. Twenty-three infants and 24 adults were included in the analyses. The masked thresholds versus masker intensity data were used to estimate minimum masking levels (MMLs). RESULTS: Group mean unmasked thresholds of infants were greater than those of adults at both frequencies and the difference was greater at 0.5 kHz (14.2 dB) than at 2 kHz (5.5 dB). Infant MMLs were greater than those of adults by 10.1 dB at 0.5 kHz and by 1.2 dB at 2 kHz. The fact that a masker had to be 10.1 dB greater in intensity for infants than for adults at 0.5 kHz and 1.2 dB greater at 2 kHz suggests that there is a difference in sensitivity between the groups of about 10 and 1 dB for the two frequencies, respectively. According to a proposed model, the difference between infants and adults in MMLs is less than the difference in unmasked thresholds owing to the influence of nonsensory factors that bias infant unmasked thresholds. Such factors, therefore, contribute 4.1 dB (i.e., 14.2 dB-10.1 dB) at 0.5 kHz and 4.3 dB (i.e., 5.5 dB-1.2 dB) at 2 kHz based on the data. CONCLUSIONS: The infant-adult differences in unmasked thresholds, with greater difference at 0.5 kHz than at 2 kHz, are consistent with earlier research on infant hearing. The data reveal that the greater difference between infants and adults at 0.5 kHz relative to 2 kHz is not a result of nonsensory factors alone, but is largely due to a difference in sensory processing. Only about 4 dB of the difference between infants and adults in unmasked thresholds can be attributed to nonsensory factors and the effect is not frequency specific according to the proposed model. Consideration of establishing audiometric reference values for infants that are different than those based on adults, owing to the elevated behavioral unmasked thresholds of normal-hearing infants, is suggested.     

The relationship between the visual contribution to speech perception and lipreading ability during focused and divided attention

The study compared the lipreading ability of normal-hearing subjects during focused and divided attention and related these measures to the visual contribution to audiovisual perception. Measurement of lipreading ability during divided attention was achieved through the use of a dual-task procedure in which subjects were required to visually identify stimulus items simultaneously with the performance of an auditory processing task. The divided attention condition served to decrease lipreading performance and increase recognition variability among subjects. Lipreading ability during divided attention was more highly correlated to visual contribution magnitude, defined as the difference between audiovisual and auditory-only recognition scores, than was lipreading ability measured during focused attention. Results are related to existing models of attention which attribute dual-task decrements to processing capacity limitations.     

Comparison of speech recognition with different speech coding strategies (SPEAK, CIS, and ACE) and their relationship to telemetric measures of compound action potentials in the nucleus CI 24M cochlear implant system

Speech understanding and subjective preference for three different speech coding strategies (spectral peak coding [SPEAK], continuous interleaved sampling [CIS], and advanced combination encoders [ACE]) were investigated in 11 post-lingually deaf adult subjects, using the Nucleus CI 24M cochlear implant system. Subjects were randomly assigned to two groups in a balanced crossover study design. The first group was initially fitted with SPEAK and the second group with CIS. The remaining strategies were tested sequentially over 8 to 10 weeks with systematic variations of number of channels and rate of stimulation. Following a further interval of 3 months, during which subjects were allowed to listen with their preferred strategy, they were tested again with all three strategies. Compound action potentials (CAPs) were recorded using neural response telemetry. Input/output functions in relation to increasing stimulus levels and inter-stimulus intervals between masker and probe were established to assess the physiological status of the cochlear nerve. Objective results and subjective rating showed significant differences in favour of the ACE strategy. Ten of the 11 subjects preferred the ACE strategy at the end of the study. The estimate of the refractory period based on the inter-stimulus interval correlated significantly with the overall performance with all three strategies, but CAP measures could not be related to individual preference of strategy or differences in performance between strategies. Based on these results, the ACE strategy can be recommended as an initial choice specifically for the Nucleus CI 24M cochlear implant system. Nevertheless, access to the other strategies may help to increase performance in individual patients.     

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

Abstract

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 μV. However, 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.

Sumario

El dispositivo Nucleus CI24RE “Freedom” ofrece tasas de estimulación mayores, y menores niveles de ruido en las mediciones del potencial de acción (ECAPs) que los dispositivos anteriores. Un estudio que incluyó diez grupos europeos de implantes, mostró que el efecto de los cambios en la tasa de 250 a 3500 pulsos por segundo en la inclinación y la curvatura de los perfiles T y C es insignificante. Cuando se cambian las tasas, uno puede cambiar los niveles de todos los electrodos en la misma medida. Utilizando un procedimiento automatizado, los ECAPs pueden medirse en forma rápida y confiable a un nivel de ruido de solo 1mV. Sin embargo, esto no conlleva (a) una mejoría en las correlaciones entre los parámetros de inclinación y de curvatura de los perfiles ECAP y aquellos de los perfiles de T y C. Los niveles C promedio parecen diferir marcadamente entre los centros de implante; se requiere un mejor protocolo de evaluación. Cuando se incrementa la tasa de estimulación uno debe tomar en cuenta que eso requiere una mayor carga de pulsos por segundo y mayor poder de consumo.     

Anticipatory coarticulation in the speech of adults and young children: acoustic, perceptual, and video data.

Three experiments investigated anticipatory lingual and labial coarticulation in the [sV] productions of children and adults. Acoustic, perceptual, and video data were used to trace the development of intrasyllabic coarticulation in the speech of adults and children (ages 3, 5, and 8 years). Although children show greater variability in their articulatory patterns than adults, the data do not support claims that young children produce a greater degree of intrasyllabic coarticulation than older children or adults. Rather, the acoustic and video data suggest that young children and adults produce similar patterns of anticipatory coarticulation, and the perceptual data indicate that coarticulatory cues in the speech of 3-year-old children are less perceptible than those of the other age groups.     

儿童人工耳蜗植入术后神经反应遥测阈值与行为反应值的关系

目的 :本文通过分析儿童人工耳蜗植入术后神经反应遥测 (neural response telemetry,NRT)阈值与行为反应阈值 (T- level,T级 )及最大舒适级 (C- level,C级 )的关系 ,试图为小年龄、合并其它残疾或不能配合调试的儿童客观估算术后行为反应 T、C级提供依据。方法 :受试对象为使用 Nucleus CI2 4 M型多导人工耳蜗系统的 5 4例儿童患者。测试软件为 NRT2 .0 4版本。硬件包括计算机、IF5 (Interface 5 )卡、调试控制界面 (processor control interface,PCI)及多导人工耳蜗系统。 NRT阈值的测试采用单极刺激方式 (monopolar stimulation mode) ,分别测试每一例患者的第 3、5、10、15、2 0号电极。 T、C级测试均于 NRT测试同日进行。结果 :5 4例患者的 2 5 4个电极的波形检出率为 92 .1%。所有电极的NRT阈值均大于 T级 ,NRT阈值超过 C级的电极占 31.5 %。NRT阈值的均值介于 T级和 C级的均值之间。NRT阈值与 T级的相关系数为 r=0 .4 3(P =0 .0 0 0 0 ) ,而 NRT阈值和 C级的相关系数为 r=0 .4 8(P =0 .0 0 0 0 ) ,这些相关关系为中等强度但却具有显著性。结论 :NRT阈值的测试为不能配合术后调试的儿童患者的行为反应 T级和 C级的估算提供了客观的方法。 NRT阈值、T级和 C级的个体差异较大 ,尚不能单独根据 NRT阈     

The contributions of audibility and cognitive factors to the benefit provided by amplified speech to older adults

In this review of recent studies from our laboratory at Indiana University, it is argued that audibility is the primary contributor to the speech-understanding difficulties of older adults in unaided listening, but that other factors, especially cognitive factors, emerge when the role of audibility has been minimized. The advantages and disadvantages of three basic approaches used in our laboratory to minimize the role of audibility are examined. The first of these made use of clinical fits of personal amplification devices, but generally failed to make the aided speech stimuli sufficiently audible for the listeners. As a result, hearing loss remained the predominant predictor of performance. The second approach made use of raised and spectrally shaped stimuli with identical shaping applied for all listeners. The third approach used spectrally shaped speech that ensured audibility (at least 10 dB sensation level) of the stimuli up to at least 4000 Hz for each individual listener. With few exceptions, the importance of cognitive factors was revealed once the speech stimuli were made sufficiently audible.