Reorganization of the adult auditory system: perceptual and physiological evidence from monaural fitting of hearing aids

Acoustic deprivation modulates central gain in human auditory brainstem and cortex

Beyond reduced audibility, there is convincing evidence that the auditory system adapts according to the principles of homeostatic plasticity in response to a hearing loss. Such compensatory changes include modulation of central auditory gain mechanisms. Earplugging is a common experimental method that has been used to introduce a temporary, reversible hearing loss that induces changes consistent with central gain modulation. In the present study, young, normal-hearing adult participants wore a unilateral earplug for two weeks, during which we measured changes in the acoustic reflex threshold (ART), loudness perception, and cortically-evoked (40 Hz) auditory steady-state response (ASSR) to assess potential modulation in central gain with reduced peripheral input. The ART decreased on average by 8 to 10 dB during the treatment period, with modest increases in loudness perception after one week but not after two weeks of earplug use. Significant changes in both the magnitude and hemispheric laterality of source-localized cortical ASSR measures revealed asymmetrical changes in stimulus-driven cortical activity over time. The ART results following unilateral earplugging are consistent with the literature and suggest that homeostatic plasticity is evident in the brainstem. The novel findings from the cortical ASSR in the present study indicates that reduced peripheral input induces adaptive homeostatic plasticity reflected as both an increase in central gain in the auditory brainstem and reduced cortical activity ipsilateral to the deprived ear. Both the ART and the novel use of the 40-Hz ASSR provide sensitive measures of central gain modulation in the brainstem and cortex of young, normal hearing listeners, and thus may be useful in future studies with other clinical populations.

Hearing Aids Mitigate Tinnitus, But Does It Matter if the Patient Receives Amplification in Accordance With Their Hearing Impairment or Not? A Meta-Analysis

PURPOSE

The purpose of the present meta-analysis is to explore the potential effects of objective verification of hearing aid amplification on tinnitus-related outcomes.

METHOD

Twenty-seven studies reporting tinnitus outcomes pre and post hearing aid fitting were identified through a systematic literature search. From these studies, data from 1,400 participants were included in the present meta-analysis. Studies were divided into subgroups based on whether they had reported performing objective verification of the participants' hearing aid amplification or not. Outcome measures were tinnitus distress and tinnitus loudness.

RESULTS

Meta-analyses of all included studies indicated verified amplification to result in significantly enhanced reduction of tinnitus loudness (p < .00001), while the enhanced reduction of tinnitus distress only approached statistical significance (p = .07). However, when excluding an outlier from the subgroup of studies using unverified amplification, individuals receiving verified amplification showed significantly greater reduction of tinnitus distress (p = .02). In addition, analyses of longitudinal effects revealed that the reductions of tinnitus distress decreased over time among individuals receiving unverified amplification but increased over time among individuals receiving verified amplification.

CONCLUSIONS

The present meta-analysis indicates verified hearing aid amplification to be superior to unverified amplification in terms of reduction of tinnitus loudness and distress. The longitudinal increase of mitigation of tinnitus distress with verified amplification only may reflect improved neural reorganization and/or better adherence to hearing aid use, with verified compared to unverified amplification. Due to the low cost of hearing aid verification compared to the high societal cost of tinnitus, objective verification of hearing aid amplification for tinnitus patients is recommended.

Applying the Hearing Aid Fitting Standard to Selection for Adults

The recent hearing aid fitting standard for adults outlines the minimum practice for audiologists fitting adult patients with hearing loss. This article focuses on three items of the standard (5, 6, and 7), which focus on the selection of unilateral/bilateral hearing aids, hearing aid style, and coupling, in addition to feature selection. The standard emphasizes that decisions around these three aspects should be recommended for a patient in an individualized manner, based on their needs assessment. For these decisions, the needs assessment might include measures of speech-in-noise ability, social network size, patient preference, and a trial period. Additional elements could include assessments of manual dexterity, binaural interference, and attitude toward hearing aids. However, there are a multitude of ways to practice clinically and still meet the items outlined in the standard. As long as the selection decisions consider individualized patient factors and are capable of meeting validated prescriptive targets, a clinician would be meeting the adult hearing aid fitting minimum standard guidance. In addition, despite the large number of past studies supporting these standards, additional, high-quality research including randomized, controlled, clinical trials are still needed to further support appropriate minimum standard recommendations.

Neural Plasticity Induced by Hearing Aid Use

Age-related hearing loss is one of the most prevalent health conditions in older adults. Although hearing aid technology has advanced dramatically, a large percentage of older adults do not use hearing aids. This untreated hearing loss may accelerate declines in cognitive and neural function and dramatically affect the quality of life. Our previous findings have shown that the use of hearing aids improves cortical and cognitive function and offsets subcortical physiological decline. The current study tested the time course of neural adaptation to hearing aids over the course of 6 months and aimed to determine whether early measures of cortical processing predict the capacity for neural plasticity. Seventeen (9 females) older adults (mean age = 75 years) with age-related hearing loss with no history of hearing aid use were fit with bilateral hearing aids and tested in six testing sessions. Neural changes were observed as early as 2 weeks following the initial fitting of hearing aids. Increases in N1 amplitudes were observed as early as 2 weeks following the hearing aid fitting, whereas changes in P2 amplitudes were not observed until 12 weeks of hearing aid use. The findings suggest that increased audibility through hearing aids may facilitate rapid increases in cortical detection, but a longer time period of exposure to amplified sound may be required to integrate features of the signal and form auditory object representations. The results also showed a relationship between neural responses in earlier sessions and the change predicted after 6 months of the use of hearing aids. This study demonstrates rapid cortical adaptation to increased auditory input. Knowledge of the time course of neural adaptation may aid audiologists in counseling their patients, especially those who are struggling to adjust to amplification. A future comparison of a control group with no use of hearing aids that undergoes the same testing sessions as the study's group will validate these findings.

Plastic changes in speech perception in older adults with hearing impairment following hearing aid use: a systematic review

OBJECTIVE

Whether hearing aid use in older adults modifies speech perception over time is not clear. To address this question, we systematically reviewed studies in which older first-time hearing aid users and controls were followed over time.

DESIGN

The review was pre-registered in PROSPERO and performed in accordance with the statement on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The question, inclusion and exclusion criteria were defined using the Population, Intervention, Control, Outcomes and Study design (PICOS) framework. Studies with no controls, studies in which participants and controls were tested at only one-time point, with no follow-up and no pre-fitting measures, or when outcome measures did not include speech measures, were excluded.

STUDY SAMPLE

6113 studies were screened, out of which 12 studies, published between 1996 and 2021, met the inclusion and exclusion criteria and were included in the final review.

RESULTS

9 of the 12 studies found evidence for amplification-induced auditory plasticity in older adults, expressed in improved speech perception.

CONCLUSIONS

The results suggest amplification-induced improvements in speech perception over time, but findings should be interpreted with caution because overall improvements were small, and the studies' quality was moderate.

Hearing Aids Reduce Daily-Life Fatigue and Increase Social Activity: A Longitudinal Study

People with hearing loss experience fatigue, and it is unknown whether this is alleviated by treatment with hearing aids. The objective of this study was to address this issue and to investigate the possible concomitant effect of hearing-aid fitting on activity levels. An intervention group (n = 53) who were due to be fitted with their first-ever hearing aid(s) and a control group (n = 53) who had hearing loss but no change in hearing aid status-completed a battery of self-report outcome measures four times: once before fitting, and at 2 weeks, 3 months, and 6 months post fitting. Self-report outcome measures at each assessment captured fatigue, listening effort, hearing handicap, auditory lifestyle, social participation restrictions, and work, social and physical activity levels. Hearing-aid fitting led to a significant reduction in listening-related fatigue, but not general fatigue, in the intervention group compared to the control group. Additionally, social activity level increased and social participation restriction decreased significantly after hearing aid fitting in the intervention group compared to the control group. No significant interaction was found between working status and change in listening-related fatigue score. This study is the first to make a longitudinal measurement of fatigue before and after first-ever hearing aid fitting and to identify an increase in social activity level after hearing aid fitting. These findings have important implications for future research and the clinical practice of hearing aid fitting.

Neural Representation Enhanced for Speech and Reduced for Background Noise With a Hearing Aid Noise Reduction Scheme During a Selective Attention Task

Objectives

Selectively attending to a target talker while ignoring multiple interferers (competing talkers and background noise) is more difficult for hearing-impaired (HI) individuals compared to normal-hearing (NH) listeners. Such tasks also become more difficult as background noise levels increase. To overcome these difficulties, hearing aids (HAs) offer noise reduction (NR) schemes. The objective of this study was to investigate the effect of NR processing (inactive, where the NR feature was switched off, vs. active, where the NR feature was switched on) on the neural representation of speech envelopes across two different background noise levels [+3 dB signal-to-noise ratio (SNR) and +8 dB SNR] by using a stimulus reconstruction (SR) method.

Design

To explore how NR processing supports the listeners’ selective auditory attention, we recruited 22 HI participants fitted with HAs. To investigate the interplay between NR schemes, background noise, and neural representation of the speech envelopes, we used electroencephalography (EEG). The participants were instructed to listen to a target talker in front while ignoring a competing talker in front in the presence of multi-talker background babble noise.

Results

The results show that the neural representation of the attended speech envelope was enhanced by the active NR scheme for both background noise levels. The neural representation of the attended speech envelope at lower (+3 dB) SNR was shifted, approximately by 5 dB, toward the higher (+8 dB) SNR when the NR scheme was turned on. The neural representation of the ignored speech envelope was modulated by the NR scheme and was mostly enhanced in the conditions with more background noise. The neural representation of the background noise was modulated (i.e., reduced) by the NR scheme and was significantly reduced in the conditions with more background noise. The neural representation of the net sum of the ignored acoustic scene (ignored talker and background babble) was not modulated by the NR scheme but was significantly reduced in the conditions with a reduced level of background noise. Taken together, we showed that the active NR scheme enhanced the neural representation of both the attended and the ignored speakers and reduced the neural representation of background noise, while the net sum of the ignored acoustic scene was not enhanced.

Conclusion

Altogether our results support the hypothesis that the NR schemes in HAs serve to enhance the neural representation of speech and reduce the neural representation of background noise during a selective attention task. We contend that these results provide a neural index that could be useful for assessing the effects of HAs on auditory and cognitive processing in HI populations.

Sense and Sensibility: A Review of the Behavioral Neuroscience of Tinnitus Sound Therapy and a New Typology

Tinnitus Sound Therapy is not a single strategy. It consists of many different sound types, targeting many different mechanisms. Therapies that use sound to cover, reduce attention to, or facilitate habituation of tinnitus are among the most common tinnitus treatment paradigms. Recent history has seen a proliferation of sound therapies, but they have each been criticized for having limited empirical support. In this review, Sound Therapy's modern history will be described, and a typology will be introduced and discussed in light of current behavioral neuroscience research. It will be argued that contributing factors to the limited evidence for the efficacy of Sound Therapy are its diversity, plural modes of action, and absence of a clear typology. Despite gaps in understanding the efficacy of sound's effects on tinnitus, there is compelling evidence for its multiple, but related, neurophysiological mechanisms. Evidence suggests that sound may reduce tinnitus through its presence, context, reaction, and potentially adaptation. This review provides insights into the neurocognitive basis of these tinnitus Sound Therapy modes. It concludes that a unifying classification is needed to secure and advance arguments in favor of Sound Therapy.

Neural and behavioral changes after the use of hearing aids

OBJECTIVE

Individuals with age-related hearing loss (ARHL) can restore some loss of the auditory function with the use of hearing aids (HAs). However, what remains unknown are the physiological mechanisms that underlie how the brain changes with exposure to amplified sounds though the use of HAs. We aimed to examine behavioral and physiological changes induced by HAs.

METHODS

Thirty-five older-adults with moderate ARHL with no history of hearing aid use were fit with HAs tested in aided and unaided conditions, and divided into experimental and control groups. The experimental group used HAs during a period of six months. The control group did not use HAs during this period, but were given the opportunity to use them after the completion of the study. Both groups underwent testing protocols six months apart. Outcome measures included behavioral (speech-in-noise measures, self-assessment questionnaires) and electrophysiological brainstem recordings (frequency-following responses) to the speech syllable /ga/ in two quiet conditions and in six-talker babble noise.

RESULTS

The experimental group reported subjective benefits on self-assessment questionnaires. Significant physiological changes were observed in the experimental group, specifically a reduction in fundamental frequency magnitude, while no change was observed in controls, yielding a significant time × group interaction. Furthermore, peak latencies remained stable in the experimental group but were significantly delayed in the control group after six months. Significant correlations between behavioral and physiological changes were also observed.

CONCLUSIONS

The findings suggest that HAs may alter subcortical processing and offset neural timing delay; however, further investigation is needed to understand cortical changes and HA effects on cognitive processing.

SIGNIFICANCE

The findings of the current study provide evidence for clinicians that the use of HAs may prevent further loss of auditory function resulting from sensory deprivation.

Speech-in-noise perception in unilateral hearing loss: Relation to pure-tone thresholds and brainstem plasticity

We investigated speech recognition in noise in subjects with mild to profound levels of unilateral hearing loss. Thirty-five adults were evaluated using an adaptive signal-to-noise ratio (SNR50) sentence recognition threshold test in three spatial configurations. The results revealed a significant correlation between pure-tone average audiometric thresholds in the poorer ear and SNR thresholds in the two conditions where speech and noise were spatially separated: dichotic - with speech presented to the poorer ear and reverse dichotic - with speech presented to the better ear. This first result suggested that standard pure-tone air-conduction thresholds can be a reliable predictor of speech recognition in noise for binaural conditions. However, a subgroup of 14 subjects was found to have poorer-than-expected speech recognition scores, especially in the reverse dichotic listening condition. In this subgroup 9 subjects had been diagnosed with vestibular schwannoma at stage III or IV likely affecting the lower brainstem function. These subjects showed SNR thresholds in the reverse dichotic condition on average 4dB poorer (higher) than for the other 21 normally-performing subjects. For the 7 of 9 subjects whose vestibular schwannoma was removed, the deficit was no longer apparent on average 5 months following the surgical procedure. These results suggest that following unilateral hearing loss the capacity to use monaural spectral information is supported by the lower brainstem.

Assessment of hearing aid algorithms using a master hearing aid: the influence of hearing aid experience on the relationship between speech recognition and cognitive capacity

OBJECTIVES

Model-based hearing aid development considers the assessment of speech recognition using a master hearing aid (MHA). It is known that aided speech recognition in noise is related to cognitive factors such as working memory capacity (WMC). This relationship might be mediated by hearing aid experience (HAE). The aim of this study was to examine the relationship of WMC and speech recognition with a MHA for listeners with different HAE.

DESIGN

Using the MHA, unaided and aided 80% speech recognition thresholds in noise were determined. Individual WMC capacity was assed using the Verbal Learning and Memory Test (VLMT) and the Reading Span Test (RST).

STUDY SAMPLE

Forty-nine hearing aid users with mild to moderate sensorineural hearing loss divided into three groups differing in HAE.

RESULTS

Whereas unaided speech recognition did not show a significant relationship with WMC, a significant correlation could be observed between WMC and aided speech recognition. However, this only applied to listeners with HAE of up to approximately three years, and a consistent weakening of the correlation could be observed with more experience.

CONCLUSIONS

Speech recognition scores obtained in acute experiments with an MHA are less influenced by individual cognitive capacity when experienced HA users are taken into account.

Are Experienced Hearing Aid Users Faster at Grasping the Meaning of a Sentence Than Inexperienced Users? An Eye-Tracking Study

This study assessed the effects of hearing aid (HA) experience on how quickly a participant can grasp the meaning of an acoustic sentence-in-noise stimulus presented together with two similar pictures that either correctly (target) or incorrectly (competitor) depict the meaning conveyed by the sentence. Using an eye tracker, the time taken by the participant to start fixating the target (the processing time) was measured for two levels of linguistic complexity (low vs. high) and three HA conditions: clinical linear amplification (National Acoustic Laboratories-Revised), single-microphone noise reduction with National Acoustic Laboratories-Revised, and linear amplification ensuring a sensation level of ≥ 15 dB up to at least 4 kHz for the speech material used here. Timed button presses to the target stimuli after the end of the sentences (offline reaction times) were also collected. Groups of experienced (eHA) and inexperienced (iHA) HA users matched in terms of age, hearing loss, and working memory capacity took part (N = 15 each). For the offline reaction times, no effects were found. In contrast, processing times increased with linguistic complexity. Furthermore, for all HA conditions, processing times were longer (poorer) for the iHA group than for the eHA group, despite comparable speech recognition performance. Taken together, these results indicate that processing times are more sensitive to speech processing-related factors than offline reaction times. Furthermore, they support the idea that HA experience positively impacts the ability to process noisy speech quickly, irrespective of the precise gain characteristics.

Hearing Aid-Induced Plasticity in the Auditory System of Older Adults: Evidence From Speech Perception

PURPOSE

We tested whether using hearing aids can improve unaided performance in speech perception tasks in older adults with hearing impairment.

METHOD

Unaided performance was evaluated in dichotic listening and speech-in-noise tests in 47 older adults with hearing impairment; 36 participants in 3 study groups were tested before hearing aid fitting and after 4, 8, and 14 weeks of hearing-aid use. The remaining 11 participants served as a control group and were similarly evaluated but were not fitted with hearing aids. Three protocols were compared in the study groups: amplification for the nondominant ear, amplification for the dominant ear, and bilateral amplification. Subsequently, after 4 weeks, all participants were afforded bilateral amplification.

RESULTS

In the study groups, unaided dichotic listening scores improved significantly in the nondominant ear by 8 weeks and onward. Significant improvements were also observed for unaided speech identification in noise, with some gains apparent after 4 weeks of hearing-aid use. No gains were observed in the control group.

CONCLUSIONS

Using hearing aids for a relatively short period can induce changes in the way older adults process auditory inputs in perceptual tasks such as speech identification in noise and dichotic listening. These changes suggest that the central auditory system of older adults retains the potential for behaviorally relevant plasticity.

Better together: reduced compliance after sequential versus simultaneous bilateral hearing aids fitting

PURPOSE

The purpose of this study was to determine the effects of sequential versus simultaneous bilateral hearing aids fitting on patient compliance.

METHOD

Thirty-six older adults with hearing impairment participated in this study. Twelve were fitted with bilateral hearing aids simultaneously. The remaining participants were fitted sequentially: One hearing aid (to the left or to the right ear) was used initially; 1 month later, the other ear was also fitted with a hearing aid for bilateral use. Self-reports on usefulness and compliance were elicited after the first and second months of hearing aid use. In addition, the number of hours the hearing aids were used was extracted from the data loggings of each device.

RESULTS

Simultaneous fitting resulted in high levels of compliance and consistent usage throughout the study period. Sequential fitting resulted in abrupt reduction in compliance and hours of use once the second hearing aid was added, both in the clinical scoring and in the data loggings.

CONCLUSIONS

Simultaneous fitting of bilateral hearing aids results in better compliance compared with sequential fitting. The addition of a second hearing aid after a relatively short period of monaural use may lead to inconsistent use of both hearing aids.

Auditory acclimatization and hearing aids: late auditory evoked potentials and speech recognition following unilateral and bilateral amplification

The aim of this study was to investigate changes in central auditory processing following unilateral and bilateral hearing aid fitting using a combination of physiological and behavioral measures: late auditory event-related potentials (ERPs) and speech recognition in noise, respectively. The hypothesis was that for fitted ears, the ERP amplitude would increase over time following hearing aid fitting in parallel with improvement in aided speech recognition. The N1 and P2 ERPs were recorded to 500 and 3000 Hz tones presented at 65, 75, and 85 dB sound pressure level to either the left or right ear. New unilateral and new bilateral hearing aid users were tested at the time of first fitting and after 12 weeks hearing aid use. A control group of long-term hearing aid users was tested over the same time frame. No significant changes in the ERP were observed for any group. There was a statistically significant 2% improvement in aided speech recognition over time for all groups, although this was consistent with a general test-retest effect. This study does not support the existence of an acclimatization effect observable in late ERPs following 12 weeks' hearing aid use.

USES AND LIMITATIONS OF ELECTROPHYSIOLOGY WITH HEARING AIDS

There is currently a strong interest among both audiologists and hearing researchers to find a physiological measure that can be used as a marker of how amplified sounds are processed by the brain (i.e., hearing aid fitting) or how the brain changes with exposure to amplified sounds (i.e., hearing aid acclimatization). Currently, auditory evoked potentials are used, or proposed to be used, for both of these purposes to some degree. It is clear from the literature that some of these uses are potentially useful clinically while others are quite problematic. The current state of aided cortical auditory evoked potentials will be discussed relative to their application to hearing aid fitting/verification and in understanding hearing aid acclimatization. Future areas of promise as well as current gaps in the literature will also be addressed.

Unilateral and bilateral hearing aids, spatial release from masking and auditory acclimatization

Spatial release from masking (SRM) was tested within the first week of fitting and after 12 weeks hearing aid use for unilateral and bilateral adult hearing aid users. A control group of experienced hearing aid users completed testing over a similar time frame. The main research aims were (1) to examine auditory acclimatization effects on SRM performance for unilateral and bilateral hearing aid users, (2) to examine whether hearing aid use, level of hearing loss, age or cognitive ability mediate acclimatization, and (3) to compare and contrast the outcome of unilateral versus bilateral aiding on SRM. Hearing aid users were tested with and without hearing aids, with SRM calculated as the 50% speech recognition threshold advantage when maskers and target are spatially separated at ±90° azimuth to the listener compared to a co-located condition. The conclusions were (1) on average there was no improvement over time in familiar aided listening conditions, (2) there was large test-retest variability which may overshadow small average acclimatization effects; greater improvement was associated with better cognitive ability and younger age, but not associated with hearing aid use, and (3) overall, bilateral aids facilitated better SRM performance than unilateral aids.

Benefício fornecido pelo uso de aparelhos de amplificação sonora individual em idosos de um programa de saude auditiva de Porto Velho - RO

OBJETIVO: verificar o benefício do aparelho de amplificação sonora individual na população idosa de Porto Velho, Rondônia e região, além de comparar os achados encontrados com o grau da perda auditiva instalada na população estudada. MÉODO: fizeram parte deste estudo 18 idosos com idade entre 60 e 82 anos, portadores de deficiência auditiva neurossensorial de grau leve a moderadamente severo. O benefício foi avaliado por meio do questionário Abbreviated Profile of Hearing Aid Benefit - APHAB, nas condições sem e com prótese auditiva, sendo tal questionário aplicado no momento da adaptação e três meses após a mesma. Para análise das respostas foram consideradas as seguintes subescalas: Facilidade de comunicação, ruído ambiental, ruído reverberante e aversão a sons. O benefício obtido por subescala foi comparado com o grau da perda auditiva de cada sujeito. RESULTADOS: foi verificado benefício nas subescalas facilidade de comunicação, ruído ambiental e ruído reverberante, tendo tal achado apresentado diferença estatisticamente significante. Quanto à relação do benefício com o grau da perda, verificou-se, dentre os sujeitos com perda auditiva simétrica, maior benefício nos que apresentavam perda auditiva neurossensorial de grau moderado, porém dentre os indivíduos com perdas auditivas de graus diferentes, não foi possível verificar relação entre o grau da perda e o benefício obtido pelos mesmos. CONCLUSÃO: houve redução das dificuldades auditivas com o uso da amplificação sonora em ambientes favoráveis, reverberantes e com elevado nível de ruído.

Hearing aid fitting and unilateral auditory deprivation: behavioral and electrophysiologic assessment

The phenomenon of Late-Onset Unilateral Auditory Deprivation was first reported in 1984. However, a high number of unilateral hearing aid fittings are still carried out in cases of bilateral hearing loss, justified by non-auditory factors such as cost, vanity, misinformation and public health policies.

Objective

To carry out behavioral and electrophysiological assessment of the auditory performance of adults using unilateral amplification compared with individuals exposed to bilateral symmetric auditory stimulation.

Method

Thirty five adults, all with symmetric bilateral sensorineural hearing loss, regular users of unilateral hearing aid, bilateral hearing aids and not users of hearing aids, were assessed on behavioral and electrophysiological tests.

Results

Variance analysis revealed that in the unilaterally fitted group, P300 latency was significantly greater in ears with auditory deprivation compared with those fitted with the hearing aid (p < 0.05). This same group also had poorer performance on the Sentence Recognition Test in Noise held in free field.

Conclusion

These results corroborate findings in the literature showing that unilateral auditory deprivation can lead to physiological and perceptual changes.

Evaluation of Speech Intelligibility and Sound Localization Abilities with Hearing Aids Using Binaural Wireless Technology

Wireless synchronization of the digital signal processing (DSP) features between two hearing aids in a bilateral hearing aid fitting is a fairly new technology. This technology is expected to preserve the differences in time and intensity between the two ears by co-ordinating the bilateral DSP features such as multichannel compression, noise reduction, and adaptive directionality. The purpose of this study was to evaluate the benefits of wireless communication as implemented in two commercially available hearing aids. More specifically, this study measured speech intelligibility and sound localization abilities of normal hearing and hearing impaired listeners using bilateral hearing aids with wireless synchronization of multichannel Wide Dynamic Range Compression (WDRC). Twenty subjects participated; 8 had normal hearing and 12 had bilaterally symmetrical sensorineural hearing loss. Each individual completed the Hearing in Noise Test (HINT) and a sound localization test with two types of stimuli. No specific benefit from wireless WDRC synchronization was observed for the HINT; however, hearing impaired listeners had better localization with the wireless synchronization. Binaural wireless technology in hearing aids may improve localization abilities although the possible effect appears to be small at the initial fitting. With adaptation, the hearing aids with synchronized signal processing may lead to an improvement in localization and speech intelligibility. Further research is required to demonstrate the effect of adaptation to the hearing aids with synchronized signal processing on different aspects of auditory performance.

Health-related quality of life before and after management in adults referred to otolaryngology: a prospective national study

Objective

An assessment of the effect of otolaryngological management on the health-related quality of life of patients.

Design

Application of the Health Utilities Index mark 3 (HUI-3) before and after treatment; application of the Glasgow Benefit Inventory (GBI) after treatment.

Setting

Six otolaryngological departments around Scotland.

Participants

A 9005 adult patients referred to outpatient clinics.

Main outcome measures

Complete HUI-3 data was collected from 4422 patients; complete GBI data from 4235; complete HUI-3 and GBI data from 3884.

Results

The overall change in health related quality of life from before to after management was just +0.02. In the majority of subgroups of data (classified by type of management) there was essentially no change in HUI-3 score. The major exceptions were those patients provided with a hearing aid (mean change 0.08) and those whose problem was managed surgically (mean change 0.04). The mean GBI score was 5.3 which is low. Those managed surgically reported a higher GBI score of 13.0.

Conclusion

We found that patients treated surgically or given a hearing aid reported a significant improvement in their health related quality of life after treatment in otolaryngology departments. In general, patients treated in other ways reported no significant improvement. We argue that future research should look carefully at patient groups where there is unexpectedly little benefit from current treatment methods and consider more effective methods of management.

Relative importance of monaural sound deprivation and bilateral significant hearing loss in predicting cochlear implantation outcomes

OBJECTIVES

Making evidence-based recommendations to prospective unilateral cochlear implant recipients on the potential benefits of implanting one or the other ear is challenging for cochlear implant teams. This particularly occurs in cases where a hearing aid has only been used in one ear for many years (referred to here as the "hearing ear"), and the contralateral ear has, in essence, been sound-deprived. In such cases, research to date is inconclusive, and little anecdotal evidence exists to inform the debate and support best clinical practice.

DESIGN

Retrospective data on speech recognition outcomes of 16 adult participants who received a cochlear implant in an ear deprived of sound for a minimum of 15 yr were analyzed. All subjects were implanted through the Quebec Cochlear Implant Program and were provided with personalized intensive rehabilitation services. Data obtained from clinical records included demographic data and speech recognition scores measured after implantation with the sentences of a multimedia auditory test battery in the auditory-only condition. Speech recognition outcomes were compared with the duration of auditory deprivation in the implanted ear, bilateral significant hearing loss, and auditory stimulation before bilateral significant hearing loss.

RESULTS

Using nonparametric correlation analyses, a strong negative correlation was demonstrated between speech recognition scores and the duration of bilateral significant hearing loss and with the duration of auditory stimulation before bilateral significant hearing loss. No significant correlation with the duration of auditory deprivation or with the duration of prior auditory stimulation in the implanted ear was found.

CONCLUSIONS

These findings suggest that functional outcomes of cochlear implantation for unilateral sound deprivation may be more strongly influenced by central processes than peripheral effects stemming from the deprivation per se. This indicates the relevance of considering the client's history of binaural hearing rather than the hearing in each ear individually when discussing possible outcomes with a cochlear implant.

Late auditory evoked potentials in elderly long-term hearing-aid users with unilateral or bilateral fittings

This study investigated the effects of long-term unilateral and bilateral amplification on central auditory processing in elderly people with symmetrical hearing loss using late auditory evoked potentials. It was hypothesized that in the unilateral setting stimulation of the aided ear would yield an acclimatization effect with larger amplitudes and shorter latencies of the components P1, N1 and P2 compared to those of the unaided ear. Auditory evoked potentials were elicited by 500, 1000 and 2000 Hz pure tones at 55, 70 and 85 dB SPL presentation level delivered either to the left or right ear. Unilaterally and bilaterally fitted experienced hearing-aid users and a control group of normally hearing adults, all aged at least 60 years, participated. The responses of the unilateral hearing-aid users did not differ significantly for any of the components P1, N1 or P2 between the aided and unaided ears, but a significant interaction between ear and frequency was present for P2 amplitudes. P2 amplitudes were significantly smaller for the 0.5- and 1-kHz stimuli and tended to be larger for the 2-kHz stimulus in the aided ear suggesting an acclimatization effect. Larger P2 amplitudes were observed in the unilaterally fitted group, which was interpreted as a correlate of more effortful auditory processing in unilaterally fitted people.

Acclimatization effect in speech recognition: evaluation without hearing aids

BACKGROUND

After the adaptation of hearing aids, an improvement in speech understanding is expected to occur, called acclimatization.

AIM

To determine the effect of acclimatization in sentences recognition threshold, for the conditions of silence (SRTQ) and noise (SRTN), in new users of hearing aids, evaluated prior to and after acclimatization, without the use of the hearing aids.

METHOD

Participants were 40 individuals, aged between 28 and 78 years, with mild to moderate sensorineural hearing loss. Tests were conducted in three sessions: prior to the adaptation of the hearing aids, fourteen days and three months later.The Portuguese Sentences Lists test in free field was used for testing, and the SRTQ and SRTN were obtained (with noise level settled at 65 dB A). Results were expressed through the signal/noise ratios.

RESULTS

The mean values for the SRTQ in the 1st, 2nd and 3rd sessions were 54.43, 51.71 and 52.22 dB A respectively,. The mean signal/noise ratios for the 1st, 2nd and 3rd sessions were 1.67, 0.30 and -0.03 dB A. When comparing the results obtained between the testing sessions, a statistically significant difference was observed between the 1st and 2nd sessions, and between the 1st and 3rd sessions for the values obtained in the testing conditions of silence and noise.

CONCLUSION

There was a progressive reduction of sentences recognition thresholds and signal/noise ratios indicating an improvement in performance even when assessing the individuals without the hearing aids. This improvement can be related to the effect of acclimatization.

Índice percentual de reconhecimento de sentenças no silêncio e no ruído: efeitos da aclimatização no indivíduo avaliado sem as próteses auditivas

OBJETIVO: verificar o efeito da aclimatização no reconhecimento de sentenças no silêncio e no ruído, em novos usuários de próteses auditivas, avaliados sem as mesmas, antes e após o período de aclimatização. MÉTODOS: participaram do estudo 40 indivíduos, idade entre 28 e 78 anos, que possuíam perda auditiva neurossensorial de grau leve a moderadamente severo, e estavam iniciando o processo de seleção e adaptação de próteses auditivas. Os testes foram realizados em diferentes sessões: antes da adaptação das próteses auditivas, 14 dias e três meses após a adaptação. Foi aplicado o teste Listas de Sentenças em Português (COSTA, 1997), em campo livre, no silêncio e no ruído, ambos em intensidade fixa de 65 dB A, na qual foram obtidos os índices percentuais de reconhecimento de sentenças no silêncio (IPRSS) e no ruído (IPRSR). RESULTADOS: os valores médios obtidos para o IPRSS na 1ª, 2ª e 3ª sessões foram, respectivamente, 65%; 72% e 83% dB A. Já as médias dos IPRSR para a 1ª, 2ª e 3ª sessões foram 51%; 58% e 59% dB A. Ao comparar os resultados obtidos entre as sessões, foi verificada diferença estatisticamente significante, para o IPRSS, entre 1ª e a 3ª e entre a 2ª e a 3ª sessão e, para o IPRSR, entre a 1ª e a 2ª e entre a 1ª e a 3ª sessão. CONCLUSÃO: os indivíduos melhoraram seu desempenho ao longo do uso das próteses auditivas, mesmo sendo avaliados sem as mesmas e essa melhora pode estar relacionada ao efeito da aclimatização.