Auditory Performance and Electrical Stimulation Measures in Cochlear Implant Recipients With Auditory Neuropathy Compared With Severe to Profound Sensorineural Hearing Loss.

Objectives: The aim of the study was to compare auditory and speech outcomes and electrical parameters on average 8 years after cochlear implantation between children with isolated auditory neuropathy (AN) and children with sensorineural hearing loss (SNHL). Design: The study was conducted at a tertiary, university-affiliated pediatric medical center. The cohort included 16 patients with isolated AN with current age of 5 to 12.2 years who had been using a cochlear implant for at least 3.4 years and 16 control patients with SNHL matched for duration of deafness, age at implantation, type of implant, and unilateral/bilateral implant placement. All participants had had extensive auditory rehabilitation before and after implantation, including the use of conventional hearing aids. Most patients received Cochlear Nucleus devices, and the remainder either Med-El or Advanced Bionics devices. Unaided pure-tone audiograms were evaluated before and after implantation. Implantation outcomes were assessed by auditory and speech recognition tests in quiet and in noise. Data were also collected on the educational setting at 1 year after implantation and at school age. The electrical stimulation measures were evaluated only in the Cochlear Nucleus implant recipients in the two groups. Similar mapping and electrical measurement techniques were used in the two groups. Electrical thresholds, comfortable level, dynamic range, and objective neural response telemetry threshold were measured across the 22-electrode array in each patient. Main outcome measures were between-group differences in the following parameters: (1) Auditory and speech tests. (2) Residual hearing. (3) Electrical stimulation parameters. (4) Correlations of residual hearing at low frequencies with electrical thresholds at the basal, middle, and apical electrodes. Results: The children with isolated AN performed equally well to the children with SNHL on auditory and speech recognition tests in both quiet and noise. More children in the AN group than the SNHL group were attending mainstream educational settings at school age, but the difference was not statistically significant. Significant between-group differences were noted in electrical measurements: the AN group was characterized by a lower current charge to reach subjective electrical thresholds, lower comfortable level and dynamic range, and lower telemetric neural response threshold. Based on pure-tone audiograms, the children with AN also had more residual hearing before and after implantation. Highly positive coefficients were found on correlation analysis between T levels across the basal and midcochlear electrodes and low-frequency acoustic thresholds. Conclusions: Prelingual children with isolated AN who fail to show expected oral and auditory progress after extensive rehabilitation with conventional hearing aids should be considered for cochlear implantation. Children with isolated AN had similar pattern as children with SNHL on auditory performance tests after cochlear implantation. The lower current charge required to evoke subjective and objective electrical thresholds in children with AN compared with children with SNHL may be attributed to the contribution to electrophonic hearing from the remaining neurons and hair cells. In addition, it is also possible that mechanical stimulation of the basilar membrane, as in acoustic stimulation, is added to the electrical stimulation of the cochlear implant. Copyright (C) 2016 Wolters Kluwer Health, Inc. All rights reserved.

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Auditory Brainstem Response Altered in Humans With Noise Exposure Despite Normal Outer Hair Cell Function.

Objectives: Recent animal studies demonstrated that cochlear synaptopathy, a partial loss of inner hair cell-auditory nerve fiber synapses, can occur in response to noise exposure without any permanent auditory threshold shift. In animal models, this synaptopathy is associated with a reduction in the amplitude of wave I of the auditory brainstem response (ABR). The goal of this study was to determine whether higher lifetime noise exposure histories in young people with clinically normal pure-tone thresholds are associated with lower ABR wave I amplitudes. Design: Twenty-nine young military Veterans and 35 non Veterans (19 to 35 years of age) with normal pure-tone thresholds were assigned to 1 of 4 groups based on their self-reported lifetime noise exposure history and Veteran status. Suprathreshold ABR measurements in response to alternating polarity tone bursts were obtained at 1, 3, 4, and 6 kHz with gold foil tiptrode electrodes placed in the ear canal. Wave I amplitude was calculated from the difference in voltage at the positive peak and the voltage at the following negative trough. Distortion product otoacoustic emission input/output functions were collected in each participant at the same four frequencies to assess outer hair cell function. Results: After controlling for individual differences in sex and distortion product otoacoustic emission amplitude, the groups containing participants with higher reported histories of noise exposure had smaller ABR wave I amplitudes at suprathreshold levels across all four frequencies compared with the groups with less history of noise exposure. Conclusions: Suprathreshold ABR wave I amplitudes were reduced in Veterans reporting high levels of military noise exposure and in non Veterans reporting any history of firearm use as compared with Veterans and non Veterans with lower levels of reported noise exposure history. The reduction in ABR wave I amplitude in the groups with higher levels of noise exposure cannot be accounted for by sex or variability in outer hair cell function. This change is similar to the decreased ABR wave I amplitudes observed in animal models of noise-induced cochlear synaptopathy. However, without post mortem examination of the temporal bone, no direct conclusions can be drawn concerning the presence of synaptopathy in the study groups with higher noise exposure histories. Copyright (C) 2016 Wolters Kluwer Health, Inc. All rights reserved.

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Evaluating the Precision of Auditory Sensory Memory as an Index of Intrusion in Tinnitus.

Objectives: The purpose of this study was to investigate the potential of measures of auditory short-term memory (ASTM) to provide a clinical measure of intrusion in tinnitus. Design: Response functions for six normal listeners on a delayed pitch discrimination task were contrasted in three conditions designed to manipulate attention in the presence and absence of simulated tinnitus: (1) no-tinnitus, (2) ignore-tinnitus, and (3) attend-tinnitus. Results: Delayed pitch discrimination functions were more variable in the presence of simulated tinnitus when listeners were asked to divide attention between the primary task and the amplitude of the tinnitus tone. Conclusions: Changes in the variability of auditory short-term memory may provide a novel means of quantifying the level of intrusion associated with the tinnitus percept during listening. Copyright (C) 2016 Wolters Kluwer Health, Inc. All rights reserved.

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The Effect of Cochlear Damage on the Sensitivity to Harmonicity.

Objectives: A sum of simultaneous pure tones with harmonic relationships (i.e., simple frequency ratios) is normally heard as a single sound, with a single pitch, even when its components are fully resolved in the auditory periphery. This perceptual phenomenon called "harmonic fusion" is thought to play an important role in auditory scene analysis as listeners often have to segregate simultaneous harmonic sounds with different fundamental frequencies. The present study explored the consequences of mild or moderate cochlear hearing loss for the sensitivity to harmonicity and the detection of inharmonicity. Design: The subjects were 12 normal-hearing (NH) listeners and 8 listeners with cochlear hearing loss amounting to 30 to 50 dB (mean: 42 dB) from 0.25 to 3 kHz. In each subject, thresholds for the detection of a change in the frequency ratio of simultaneous pure tones were measured with an adaptive forced-choice procedure. The standard frequency ratio was either harmonic (2:1, i.e., one octave) or inharmonic (0.8 or 1.2 octaves). The tones were presented at a low sensation level (at most 15 dB) within broadband noise, to minimize their cochlear interactions. In the main experimental conditions, the frequency register of the stimuli varied randomly within each trial, so that subjects were forced to process frequency ratios to achieve good performance; frequency discrimination was not sufficient. In other conditions, by contrast, frequency discrimination was sufficient to perform the task optimally. Results: For both groups of subjects, thresholds in the main experimental conditions were lower (i.e., better) when the standard frequency ratio was harmonic than when it was inharmonic. This effect, revealing sensitivity to harmonicity, was weak for some members of the hearing-impaired group, but could be observed even in subjects showing a very poor frequency discrimination ability. The two groups, however, differed from each other with respect to the detection of inharmonicity: for the NH group, in agreement with previous results, negative deviations from one octave (i.e., compressions of this frequency ratio) were better detected than positive deviations (stretchings); for the hearing-impaired group, on the other hand, the sign of the deviations had no effect on performance. Conclusions: Sensitivity to harmonicity appears to be remarkably robust. However, it can be reduced in some listeners with mild or moderate cochlear damage. Moreover, as inharmonicity detection is asymmetric for NH listeners but apparently becomes symmetric in case of cochlear damage, it may be that listeners with cochlear damage do not detect inharmonicity in the same manner as NH listeners do. In some circumstances, inharmonicity can be detected on the basis of "beat" cues available in single frequency channels; however, the subjects tested here were unlikely to use cues of this type. Copyright (C) 2016 Wolters Kluwer Health, Inc. All rights reserved.

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Improving Mobile Phone Speech Recognition by Personalized Amplification: Application in People with Normal Hearing and Mild-to-Moderate Hearing Loss.

Purpose: In this study, the authors evaluated the effect of personalized amplification on mobile phone speech recognition in people with and without hearing loss. Methods: This prospective study used double-blind, within-subjects, repeated measures, controlled trials to evaluate the effectiveness of applying personalized amplification based on the hearing level captured on the mobile device. The personalized amplification settings were created using modified one-third gain targets. The participants in this study included 100 adults of age between 20 and 78 years (60 with age-adjusted normal hearing and 40 with hearing loss). The performance of the participants with personalized amplification and standard settings was compared using both subjective and speech-perception measures. Speech recognition was measured in quiet and in noise using Cantonese disyllabic words. Subjective ratings on the quality, clarity, and comfortableness of the mobile signals were measured with an 11-point visual analog scale. Subjective preferences of the settings were also obtained by a paired-comparison procedure. Results: The personalized amplification application provided better speech recognition via the mobile phone both in quiet and in noise for people with hearing impairment (improved 8 to 10%) and people with normal hearing (improved 1 to 4%). The improvement in speech recognition was significantly better for people with hearing impairment. When the average device output level was matched, more participants preferred to have the individualized gain than not to have it. Conclusions: The personalized amplification application has the potential to improve speech recognition for people with mild-to-moderate hearing loss, as well as people with normal hearing, in particular when listening in noisy environments. Copyright (C) 2016 Wolters Kluwer Health, Inc. All rights reserved.

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A Profiling System for the Assessment of Individual Needs for Rehabilitation With Hearing Aids

This study focuses on the development of a profiling system to specify the needs of hearing-aid candidates. As a basis for the profile of compensation needs, we used a slightly modified version of the Amsterdam Inventory of Disability and Handicap, combined with the well-known Client-Oriented Scale of Improvement (COSI). The first questionnaire results in scores for six audiological dimensions: detection, speech in quiet, speech in noise, localization, focus or discrimination, and noise tolerance. The goal of this study was to determine whether the six dimensions derived from the disability questionnaire are appropriate to also categorize individual COSI targets. The results show a good agreement between eight audiologists in the categorization of COSI goals along the six dimensions. The results per dimension show that the dimension focus or discrimination can be regarded as superfluous. Possible additional dimensions were tinnitus and listening effort. The results indicate that it is possible to translate individual user needs (administered using COSI) into more general dimensions derived from a disability questionnaire. This allows to summarize the compensation needs for individual patients in a profile of general dimensions, based on the degree of disability and the individual user needs. This profile can be used as a starting point in hearing aid selection. This approach also offers a well-structured method for the evaluation of the postfitting results.

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Spectrotemporal Modulation Sensitivity as a Predictor of Speech-Reception Performance in Noise With Hearing Aids

The audiogram predicts <30% of the variance in speech-reception thresholds (SRTs) for hearing-impaired (HI) listeners fitted with individualized frequency-dependent gain. The remaining variance could reflect suprathreshold distortion in the auditory pathways or nonauditory factors such as cognitive processing. The relationship between a measure of suprathreshold auditory function—spectrotemporal modulation (STM) sensitivity—and SRTs in noise was examined for 154 HI listeners fitted with individualized frequency-specific gain. SRTs were measured for 65-dB SPL sentences presented in speech-weighted noise or four-talker babble to an individually programmed master hearing aid, with the output of an ear-simulating coupler played through insert earphones. Modulation-depth detection thresholds were measured over headphones for STM (2cycles/octave density, 4-Hz rate) applied to an 85-dB SPL, 2-kHz lowpass-filtered pink-noise carrier. SRTs were correlated with both the high-frequency (2–6 kHz) pure-tone average (HFA; R² = .31) and STM sensitivity (R² = .28). Combined with the HFA, STM sensitivity significantly improved the SRT prediction (R² = .13; total R² = .44). The remaining unaccounted variance might be attributable to variability in cognitive function and other dimensions of suprathreshold distortion. STM sensitivity was most critical in predicting SRTs for listeners < 65 years old or with HFA <53 dB HL. Results are discussed in the context of previous work suggesting that STM sensitivity for low rates and low-frequency carriers is impaired by a reduced ability to use temporal fine-structure information to detect dynamic spectra. STM detection is a fast test of suprathreshold auditory function for frequencies <2 kHz that complements the HFA to predict variability in hearing-aid outcomes for speech perception in noise.

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