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.

Relationship between Behavioral and Objective Measures of Sound Intensity in Normal-Hearing Listeners and Hearing-Aid Users: A Pilot Study.

Background: For hearing-impaired individuals, hearing aids are clinically fit according to subjective measures of threshold and loudness. The goal of this study was to evaluate objective measures of loudness perception that might benefit hearing aid fitting. Method: Seventeen adult hearing aid users and 17 normal-hearing adults participated in the study. Outcome measures including categorical loudness scaling, cortical auditory evoked potentials (CAEPs), and pupillometry. Stimuli were 1-kHz tone bursts presented at 40, 60, and 80 dBA. Results: Categorical loudness scaling showed that loudness significantly increased with intensity for all participants (p < 0.05). For CAEPs, high intensity was associated with greater P1, N1, and P2 peak amplitude for all listeners (p < 0.05); a significant but small effect of hearing aid amplification was observed. For all participants, pupillometry showed significant effects of high intensity on pupil dilation (p < 0.05); there was no significant effect of hearing aid amplification. A Focused Principal Component analysis revealed significant correlations between subjective loudness and some of the objective measures. Conclusion: The present data suggest that intensity had a significant impact on loudness perception, CAEPs, and pupil response. The correlations suggest that pupillometry and/or CAEPs may be useful in determining comfortable amplification for hearing aids.

Relación entre hiperacusia y desorden del procesamiento auditivo central: Una revisión de la literatura / Relationship between hyperacusis and auditory processing disorder: a literature review

Resumen La hiperacusia corresponde a la excesiva sensibilidad auditiva o intolerancia a ciertos sonidos cotidianos que para la mayoría de las personas parecerían habituales. Considerando los mecanismos fisiológicos involucrados en el origen de la hiperacusia, es lógico pensar que su presencia podría afectar algunas habilidades del procesamiento auditivo central, sin embargo, la evidencia en torno al tema es escasa y no existe actualmente una revisión de la literatura que agrupe las investigaciones sobre esta temática. Por ello, el presente estudio pretende identificar y analizar la evidencia científica disponible sobre la relación entre hiperacusia y desorden del procesamiento auditivo central. Se realizó una revisión de la literatura guiada por protocolo PRISMA en las bases de datos Proquest, Ebsco, Pubmed, ScienceDirect, Cochrane Library y Scielo de acuerdo con términos claves. Fueron incluidos artículos originales de investigación, revisiones sistemáticas y metaanálisis, publicados desde el año 2010, realizados en animales y humanos, escritos en idiomas inglés, español y portugués. Se encontraron 323 estudios relacionados con los términos claves utilizados, de los cuales 13 cumplieron con los criterios de inclusión y fueron analizados. Se puede concluir que la evidencia científica en torno al tema es escasa e incipiente. Estructuras de la vía auditiva central como núcleos cocleares, lemnisco lateral, colículos inferiores, cuerpo geniculado medial y corteza auditiva primaria estarían relacionadas con la hiperacusia, así como también habilidades de procesamiento auditivo de figura/fondo, ordenación temporal y transferencia interhemisférica se verían afectadas.

Abstract Hyperacusis has been defined as the excessive auditory sensitivity or intolerance to certain everyday sounds that seem common for most people. Considering the underlying physiological mechanisms of hyperacusis, it is reasonable to think that it could affect some abilities involved in the central auditory processing. However, there is lack of evidence about this topic, and there is no literature review that gathers all the existing research. Therefore, the current study intends to identify and analyze the available scientific evidence regarding the relationship between hyperacusis and central auditory processing disorder. The review of the literature followed the PRISMA protocol, using key words in Proquest, Ebsco, Pubmed, ScienceDirect, Cochrane Library and Scielo databases. Original research articles, systematic reviews and meta-analyses of studies made with human and animals that have been published since 2010 in English, Spanish and Portuguese were included. Among them, 323 studies were related to the key terms, out of which 13 met the inclusion criteria and were analyzed. It is possible to conclude that there is little and incipient scientific evidence on the topic. Structures of the central auditory pathway such as cochlear nuclei, lateral lemniscus, inferior colliculi, medial geniculate body and primary auditory cortex seem to be related to hyperacusis; auditory processing skills such as figure/ground discrimination, temporal ordering and interhemispheric transfer appear to be affected as well.

Measurement of Loudness Discomfort Levels as a Test for Hyperacusis: Test-Retest Reliability and Its Clinical Value.

OBJECTIVES: The aims of this study were to investigate the test-retest reliability of measurements of loudness discomfort levels (LDLs), to suggest cut-off values for diagnosing patients with hyperacusis, and to evaluate the clinical value of-LDL measurements as a test for monitoring hyperacusis. METHODS: For the test-retest reliability of LDL measurements (study 1), a total of 68 patients who sought consultations at our clinic were subcategorized into four groups: patients with tinnitus (group 1), tinnitus and hearing loss (group 2), hyperacusis (group 3), and normal controls (group 4). Inter-hour and inter-day test-retest reliability values using different stimuli were investigated. For study 2, the clinical value of LDL measurements using pure tone stimuli was analyzed by comparing changes after sound generator use in patients with hyperacusis. RESULTS: In study 1, the group 3 patients showed significantly lower LDLs than the other groups. High test-retest reliability of LDL tests was demonstrated, regardless of the type of stimulus used. The cut-off values for screening patients with hyperacusis were 90 dB HL using pure tone stimuli and 62 dB HL using white-band noise stimuli. In study 2, significantly increased LDLs were correlated with improved symptoms and improved scores on tinnitus questionnaires after sound generator use, indicating that LDL measurement is a reliable test for monitoring hyperacusis during an intervention. CONCLUSION: LDL measurement is a reliable diagnostic tool to reflect the condition of hyperacusis, especially during the course of treatment.

Towards a Characterization of Background Music Audibility in Broadcasted TV.

In audiovisual contexts, different conventions determine the level at which background music is mixed into the final program, and sometimes, the mix renders the music to be practically or totally inaudible. From a perceptual point of view, the audibility of music is subject to auditory masking by other aural stimuli such as voice or additional sounds (e.g., applause, laughter, horns), and is also influenced by the visual content that accompanies the soundtrack, and by attentional and motivational factors. This situation is relevant to the music industry because, according to some copyright regulations, the non-audible background music must not generate any distribution rights, and the marginally audible background music must generate half of the standard value of audible music. In this study, we conduct two psychoacoustic experiments to identify several factors that influence background music perception, and their contribution to its variable audibility. Our experiments are based on auditory detection and chronometric tasks involving keyboard interactions with original TV content. From the collected data, we estimated a sound-to-music ratio range to define the audibility threshold limits of the barely audible class. In addition, results show that perception is affected by loudness level, listening condition, music sensitivity, and type of television content.

Manual Gestures Modulate Early Neural Responses in Loudness Perception.

How different sensory modalities interact to shape perception is a fundamental question in cognitive neuroscience. Previous studies in audiovisual interaction have focused on abstract levels such as categorical representation (e.g., McGurk effect). It is unclear whether the cross-modal modulation can extend to low-level perceptual attributes. This study used motional manual gestures to test whether and how the loudness perception can be modulated by visual-motion information. Specifically, we implemented a novel paradigm in which participants compared the loudness of two consecutive sounds whose intensity changes around the just noticeable difference (JND), with manual gestures concurrently presented with the second sound. In two behavioral experiments and two EEG experiments, we investigated our hypothesis that the visual-motor information in gestures would modulate loudness perception. Behavioral results showed that the gestural information biased the judgment of loudness. More importantly, the EEG results demonstrated that early auditory responses around 100 ms after sound onset (N100) were modulated by the gestures. These consistent results in four behavioral and EEG experiments suggest that visual-motor processing can integrate with auditory processing at an early perceptual stage to shape the perception of a low-level perceptual attribute such as loudness, at least under challenging listening conditions.

Detection, Speech Recognition, Loudness, and Preference Outcomes With a Direct Drive Hearing Aid: Effects of Bandwidth.

Direct drive hearing devices, which deliver a signal directly to the middle ear by vibrating the tympanic membrane via a lens placed in contact with the umbo, are designed to provide an extension of audible bandwidth, but there are few studies of the effects of these devices on preference, speech intelligibility, and loudness. The current study is the first to compare aided speech understanding between narrow and extended bandwidth conditions for listeners with hearing loss while fitted with a direct drive hearing aid system. The study also explored the effect of bandwidth on loudness perception and investigated subjective preference for bandwidth. Fifteen adult hearing aid users with symmetrical sensorineural hearing loss participated in a prospective, within-subjects, randomized single-blind repeated-measures study. Participants wore the direct drive hearing aids for 4 to 15 weeks (average 6 weeks) prior to outcome measurement. Outcome measures were completed in various bandwidth conditions achieved by reducing the gain of the device above 5000 Hz or by filtering the stimuli. Aided detection thresholds provided evidence of amplification to 10000 Hz. A significant improvement was found in high-frequency consonant detection and recognition, as well as for speech in noise performance in the full versus narrow bandwidth conditions. Subjective loudness ratings increased with provision of the full bandwidth available; however, real-world trials showed most participants were able to wear the full bandwidth hearing aids with only small adjustments to the prescription method. The majority of participants had either no preference or a preference for the full bandwidth setting.

Comparison of Relative Loudness Judgment in Children using Listening Devices with Typically Developing Children.

Introduction Loudness perception is considered important for the perception of emotions, relative distance and stress patterns. However, certain digital hearing devices worn by those with hearing impairment may affect their loudness perception. This could happen in devices that have compression circuits to make loud sounds soft and soft sounds loud. These devices could hamper children from gaining knowledge about loudness of acoustical signals. Objective To compare relative loudness judgment of children using listening devices with age-matched typically developing children. Methods The relative loudness judgment of sounds created by day-to-day objects were evaluated on 60 children (20 normal-hearing, 20 hearing aid users, & 20 cochlear implant users), utilizing a standard group comparison design. Using a two-alternate forced-choice technique, the children were required to select picturized sound sources that were louder. Results The majority of the participants obtained good scores and poorer scores were mainly obtained by children using cochlear implants. The cochlear implant users obtained significantly lower scores than the normal-hearing participants. However, the scores were not significantly different between the normal-hearing children and the hearing aid users as well as between the two groups with hearing impairment. Conclusion Thus, despite loudness being altered by listening devices, children using non-linear hearing aids or cochlear implants are able to develop relative loudness judgment for acoustic stimuli. However, loudness growth for electrical stimuli needs to be studied.

Comparison of Relative Loudness Judgment in Children using Listening Devices with Typically Developing Children

Abstract Introduction Loudness perception is considered important for the perception of emotions, relative distance and stress patterns. However, certain digital hearing devices worn by those with hearing impairment may affect their loudness perception. This could happen in devices that have compression circuits to make loud sounds soft and soft sounds loud. These devices could hamper children from gaining knowledge about loudness of acoustical signals. Objective To compare relative loudness judgment of children using listening devices with age-matched typically developing children. Methods The relative loudness judgment of sounds created by day-to-day objects were evaluated on 60 children (20 normal-hearing, 20 hearing aid users, & 20 cochlear implant users), utilizing a standard group comparison design. Using a two-alternate forced-choice technique, the children were required to select picturized sound sources that were louder. Results The majority of the participants obtained good scores and poorer scores were mainly obtained by children using cochlear implants. The cochlear implant users obtained significantly lower scores than the normal-hearing participants. However, the scores were not significantly different between the normal-hearing children and the hearing aid users as well as between the two groups with hearing impairment. Conclusion Thus, despite loudness being altered by listening devices, children using non-linear hearing aids or cochlear implants are able to develop relative loudness judgment for acoustic stimuli. However, loudness growth for electrical stimuli needs to be studied.

The influence of stimulation levels on auditory thresholds and speech recognition in adult cochlear implant users.

Objective: This study aims to evaluate the influence of minimum and maximum stimulation levels on auditory thresholds and speech recognition abilities in adult cochlear implant users. Method: Fifteen adults implanted with a Cochlear® device with over 12 months listening experience. Participants underwent routine programming for optimization of minimum (T) and maximum comfort (C) stimulation levels, which was saved in Program 1 (MO). Three further maps were constructed artificially adjusting the measured levels: Program 2 - MO with 10 fewer electrical current units at C level (MC-); Program 3 - MO with 10 fewer electric current units at T level (MT-); and Program 4 - MO with 10 more electric current units at T level (MT+). Sound field thresholds, recorded sentence recognition and monosyllable tests were presented in quiet and in noise. Results: There were significantly better thresholds at 1, 3, 4, and 6 kHz frequencies in MT+ and worse in MC-. A statistically significant difference was observed for sentences in quiet and monosyllables in quiet and noise with changing C levels, with worsening of the results for MC- program. Conclusion: The results suggest that T levels above the behavioural threshold provided an improvement in sound field thresholds but did not influence performance on speech recognition tests in quiet and in noise. In contrast, C levels below the behavioural comfort level worsened sound field thresholds and led to poorer performance in tests of sentence recognition in quiet and monosyllable recognition in quiet and in noise.

Uni- and bilateral spectral loudness summation and binaural loudness summation with loudness matching and categorical loudness scaling.

OBJECTIVE: Current hearing aid prescription rules assume that spectral loudness summation decreases with hearing impairment and that binaural loudness summation is independent of hearing loss and signal bandwidth. Previous studies have shown that these assumptions might be incorrect. Spectral loudness summation was measured and compared for loudness scaling and loudness matching. DESIGN: In this study, the effect of bandwidth on binaural summation was investigated by comparing loudness perception of low-pass filtered, high-pass filtered, and broadband pink noise at 35 Categorical Units for both unilateral and bilateral presentation. STUDY SAMPLE: Sixteen hearing-impaired listeners. RESULTS: The results show that loudness differences between the three signals are different for bilateral presentation than for unilateral presentation. In specific, binaural loudness summation is larger for the low-pass filtered pink noise than for the high-pass filtered pink noise. Finally, individual variability in loudness perception near loudness discomfort level was found to be very large. CONCLUSIONS: Loudness matching is offered as a fast and reliable method to measure individual loudness perception. As discomfort with loud sounds is one of the major problems encountered by hearing aid users, measurement of individual loudness perception could improve hearing aid fitting substantially.

Maximum Expected Information Approach for Improving Efficiency of Categorical Loudness Scaling.

Categorical loudness scaling (CLS) measures provide useful information about an individual's loudness perception across the dynamic range of hearing. A probability model of CLS categories has previously been described as a multi-category psychometric function (MCPF). In the study, a representative "catalog" of potential listener MCPFs was used in conjunction with maximum-likelihood estimation to derive CLS functions for participants with normal hearing and with hearing loss. The approach of estimating MCPFs for each listener has the potential to improve the accuracy of the CLS measurements, particularly when a relatively low number of data points are available. The present study extends the MCPF approach by using Bayesian inference to select stimulus parameters that are predicted to yield maximum expected information (MEI) during data collection. The accuracy and reliability of the MCPF-MEI approach were compared to the standardized CLS measurement procedure (ISO 16832:2006, 2006). A non-adaptive, fixed-level, paradigm served as a "gold-standard" for this comparison. The test time required to obtain measurements in the standard procedure is a major barrier to its clinical uptake. Test time was reduced from approximately 15 min to approximately 3 min with the MEI-adaptive procedure. Results indicated that the test-retest reliability and accuracy of the MCPF-MEI adaptive procedures were similar to the standardized CLS procedure. Computer simulations suggest that the reliability and accuracy of the MEI procedure were limited by intrinsic uncertainty of the listeners represented in the MCPF catalog. In other words, the MCPF provided insufficient predictive power to significantly improve adaptive-tracking efficiency under practical conditions. Concurrent optimization of both the MCPF catalog and the MEI-adaptive procedure have the potential to produce better results. Regardless of the adaptive-tracking method used in the CLS procedure, the MCPF catalog remains clinically useful for enabling maximum-likelihood determination of loudness categories.

Using auditory reaction time to measure loudness growth in rats.

Previous studies have demonstrated that auditory reaction time (RT) is a reliable surrogate of loudness perception in humans. Reaction time-intensity (RT-I) functions faithfully recapitulate equal loudness contours in humans while being easier to obtain than equal loudness judgments, especially in animals. In humans, loudness estimation not only depends on sound intensity, but on a variety of other acoustic factors. Stimulus duration and bandwidth are known to impact loudness perception. In addition, the presence of background noise mimics loudness recruitment; loudness growth is rapid near threshold, but growth becomes normal at suprathreshold levels. Therefore, to evaluate whether RT-I functions are a reliable measure of loudness growth in rats, we obtained auditory RTs across a range of stimulus intensities, durations, and bandwidths, in both quiet and in the presence of background/masking noise. We found that reaction time patterns across stimulus parameters were repeatable over several months in rats and generally consistent with human loudness perceptual data. Our results provide important building blocks for future animal model studies of loudness perception and loudness perceptual disorders.

Partial loudness at masker onset indicates temporal effects at supra-threshold levels.

This study examines temporal effects both at threshold and at supra-threshold levels. The level needed to detect a short-duration 4.0-kHz signal was measured for signals presented with different onset delays relative to a 300-ms broadband noise masker: 100 ms and 5 ms before the onset of the masker and 5 ms and 100 ms after the onset of the masker. Loudness matches between the signal in quiet and the signal at the same four onset delays were obtained for five presentation levels of the short-duration signal and for three masker levels. The temporal effect was defined as the level difference between the signals near masker onset and the signals well before or well after masker onset, needed to reach threshold and/or achieve equal loudness. Both at threshold and at supra-threshold levels temporal effects were observed consistent with a decrease in gain at the masker frequency during the course of the masker. The temporal effect was not restricted to simultaneous masking, but was also found for backward masking. In both cases the temporal effects were stronger at supra-threshold levels than at threshold. This may be caused by a transient effect at masker onset. The almost simultaneous onset of the signal and the masker makes it difficult for subjects to separate signal from the masker, especially when the signal level is close to masked threshold.

Electrically-evoked auditory steady-state responses as neural correlates of loudness growth in cochlear implant users.

Loudness growth functions characterize how the loudness percept changes with current level between the threshold and most comfortable loudness level in cochlear implant users. Even though loudness growth functions are highly listener-dependent, currently default settings are used in clinical devices. This study investigated whether electrically-evoked auditory steady-state response amplitude growth functions correspond to behaviorally measured loudness growth functions. Seven cochlear implant listeners participated in two behavioral loudness growth tasks and an EEG recording session. The 40-Hz sinusoidally amplitude-modulated pulse trains were presented to CI channels stimulating at a more apical and basal region of the cochlea, and were presented at different current levels encompassing the listeners' dynamic ranges. Behaviorally, loudness growth was measured using an Absolute Magnitude Estimation and a Graphic Rating Scale with loudness categories. A good correspondence was found between the response amplitude functions and the behavioral loudness growth functions. The results are encouraging for future advances in individual, more automatic, and objective fitting of cochlear implants.

Estimation of spectral oscillatory power of resting-state EEG in subjective tinnitus / 中国耳鼻咽喉头颈外科

OBJECTIVE To explor e the characteristics of spectral oscillatory power of resting-state electroencephalography(EEG) in subjective tinnitus patients and to lay the foundation for study of central mechanism of tinnitus.METHODS 31 subjects(15 subjects with subjective tinnitus and 16 age matching healthy subjects) underwent a 128-channel resting-state EEG analyses. After a series of preprocessing, data were segmented into 8 frequency bands, including δ(0.5～3.5 Hz), θ(4～7.5 Hz), α1(8～10 Hz), α2(10～12 Hz), β1(13～18 Hz), β2(18.5～21 Hz), β3(21.5～30 Hz) and γ(30.5～44 Hz). The group differences of spectral power were analyzed by independent t test. Correlation between spectral power of each frequency band and tinnitus subjective symptoms were also analyzed. RESULTS Significant higher spectral power of the α1, β and γ bandwere found in the left and right temporal areas of tinnitus group compared with that of normal group.Tinnitus subjects also had higher spectral powerof the δ and θ band in temporo-parietal areas than that of the normal group. There was no significant difference of spectral power in other frequency bands. Moreover, signif icant positive cor relation were found between tinnitus loudness and spectralpower of right anterior lateral(R=0.66, P =0.007) and right anterior medial(R=0.58, P =0.031) areas. CONCLUSION Tinnitus subjects have higher spectral oscillatory power on right and left temporal lobe and temporo-parietal area. A positive correlation exsit between tinnitus loudness andspectral power of right anterior lateral and medial areas in tinnitus subjects, whichindicate that central reorganizationexsit in tinnitus reorganization andγ band maybe considered as a possible biomarkerforthe tinnitus subjective symptom.

Influência da retroalimentação auditiva nos parâmetros acústicos vocais de indivíduos sem queixas vocais / Influence of auditory feedback in the vocal acoustic parameters of individuals without vocal complaints

RESUMO Introdução: A qualidade da emissão vocal é dependente da integridade do mecanismo de retroalimentação auditiva. A presença de eventuais falhas nesse mecanismo está relacionada à indução do abuso e/ ou mau uso vocal e, por conseguinte, do surgimento de quadros de disfonia. Objetivo: Avaliar a influência da retroalimentação auditiva na intensidade e na frequência da voz, em indivíduos sem queixas vocais. Métodos: Participaram da pesquisa 40 sujeitos do gênero feminino, sem queixas vocais e com limiares auditivos dentro dos padrões de normalidade. As participantes foram submetidas a uma avaliação auditiva, composta por audiometria tonal liminar, imitanciometria e por uma avaliação acústica vocal dos parâmetros de intensidade e frequência, realizada em três momentos: antes, durante e após a exposição ao ruído branco. Resultados: Houve diferença significativa na relação das médias obtidas na intensidade e entre o limiar dos reflexos acústicos contralaterais e as frequências vocais, nos três momentos da avaliação acústica. Conclusão: Os achados sugerem que a retroalimentação auditiva interfere no controle da intensidade e frequência vocal.

ABSTRACT Introduction: The quality of the vocal emission is dependent on the integrity of the auditory feedback mechanism of the presence of eventual failures is related to the induction of abuse and / or vocal misuse, and therefore of the surgeon of dysphonia. Purpose: To evaluate the influence of auditory feedback in voice intensity and frequency in individuals with no vocal complaints. Methods: Participants were 40 female subjects without vocal and auditory thresholds within normal standards complaints. Participants underwent an auditory evaluation composed of pure tone audiometry, tympanometry and a vocal acoustic assessment of intensity and frequency parameters, carried out in three stages: before, during and after exposure to white noise. Results: There was significant difference in the average of the ratio obtained in intensity and between the threshold of contralateral acoustic reflexes and vocal frequencies in the three moments of acoustic evaluation. Conclusion: Thus, the findings suggest that auditory feedback interferes with the control of the intensity and vocal frequency.

Salicylate-induced hyperacusis in rats: Dose- and frequency-dependent effects.

The use of auditory reaction time is a reliable measure of loudness perception in both animals and humans with reaction times (RT) decreasing with increasing stimulus intensity. Since abnormal loudness perception is a common feature of hyperacusis, a potentially debilitating auditory disorder in which moderate-intensity sounds are perceived as uncomfortable or painfully loud, we used RT measures to assess rats for salicylate-induced hyperacusis. A previous study using an operant conditioning RT procedure found that high-dose sodium salicylate (SS) induced hyperacusis-like behavior, i.e., faster than normal RTs to moderate and high level sounds, when rats were tested with broadband noise stimuli. However, it was not clear from that study if salicylate induces hyperacusis-like behavior in a dose- or frequency-dependent manner. Therefore, the goals of the current study were to determine how RT-intensity functions were altered by different doses of salicylate, and, using tone bursts, to determine if salicylate induces hyperacusis-like behavior across the entire frequency spectrum or only at certain frequencies. Similar to previous physiological studies, we began to see faster than normal RTs for sounds 60 dB SPL and greater with salicylate doses of 150 mg/kg and higher; indicating the rats were experiencing hyperacusis at high salicylate doses. In addition, high-dose salicylate significantly reduced RTs across all stimulus frequencies tested which suggests that a central neural excitability mechanism may be a potential driver of salicylate-induced changes in loudness perception and hyperacusis.

Functional auditory disorders.

There are a number of auditory symptom syndromes that can develop without an organic basis. Some of these, such as nonorganic hearing loss, affect populations similar to those presenting with functional somatosensory and motor symptoms, while others, such as musical hallucination, affect populations with a significantly different demographic and require different treatment strategies. Many of these conditions owe their origin to measurably abnormal peripheral sensory pathology or brain network activity, but their pathological impact is often due, at least in part, to overamplification of the salience of these phenomena. For each syndrome, this chapter briefly outlines a definition, demographics, investigations, putative mechanisms, and treatment strategies. Consideration is given to what extent they can be considered to have a functional basis. Treatments are in many cases pragmatic and rudimentary, needing more work to be done in integrating insights from behavioral and cognitive psychology to auditory neuroscience. The audiology literature has historically equated the term functional with malingering, although this perception is, thankfully, slowly changing. These disorders transcend the disciplines of audiology, otorhinolaryngology, neurology and psychiatry, and a multidisciplinary approach is often rewarding.

Adjustments of the amplitude mapping function: Sensitivity of cochlear implant users and effects on subjective preference and speech recognition.

OBJECTIVE: In sound processors of cochlear implant (CI) users, input sound signals are analysed in multiple frequency channels. The amplitude mapping function (AMF) is the output compression function dictating the conversion from (acoustical) channel output levels to (electrical) current levels used for electrode stimulation. This study focused on the detectability of AMF adjustments by CI users and the effects of detectable AMF adjustments on subjective preference and performance. DESIGN: Just noticeable differences (JNDs) for AMF settings were measured for pre-processed sentences at 60 dB SPL in quiet and noise. Three AMF settings, ranging twice the JND, were used during a take-home trial period of 12 days. Subjective ratings were collected and speech recognition in quiet and noise was measured. STUDY SAMPLE: JND measurements: 17 CI users. Field experiment: 15 CI users. RESULTS: JNDs for AMF settings varied among subjects and were similar in quiet and noise. A steeper AMF in the lower part was advantageous for speech recognition in quiet at soft levels. Subjective ratings showed limited agreement with speech recognition, both in quiet and noise. CONCLUSIONS: CI users may benefit from different AMF settings in different listening situations regarding subjective preference and speech perception, especially for speech in quiet.