Detecting the recruitment phenomenon in adults using 80-Hz auditory steady-state response.

OBJECTIVES: The ASSR is used widely as an objective measurement of hearing in clinical settings because of its high frequency specificity. The recruitment phenomenon is generally detected using subjective evaluations which require direct communication with the patient. If the recruitment phenomenon can be detected with ASSR, it would facilitate diagnosis in patients with developmental disorders and infants. SUBJECTS AND METHODS: We examined 2 groups of subjects: 10 subjects with unilateral hearing impairment in whom the recruitment phenomenon was detected by the alternate binaural loudness balance test and 12 normal subjects. We compared the relationships between the ASSR response and the stimulus sound pressure level in the 2 groups using the 80-Hz ASSR. RESULTS: The amplitude of ASSR was significantly higher in the impaired ear in hearing-impaired subjects compared to a normal ear in normal subjects. The latency of ASSR was significantly shorter in the impaired ear in hearing-impaired subjects than in the normal ear in the normal subjects. CONCLUSION: This study showed that the recruitment phenomenon caused the higher amplitude and the shorter latency observed in hearing-impaired subjects in the 80-Hz auditory steady-state response (ASSR) in comparison with normal subjects.

Effects of Hearing Loss and Fast-Acting Compression on Amplitude Modulation Perception and Speech Intelligibility.

OBJECTIVE: The purpose was to investigate the effects of hearing-loss and fast-acting compression on speech intelligibility and two measures of temporal modulation sensitivity. DESIGN: Twelve adults with normal hearing (NH) and 16 adults with mild to moderately severe sensorineural hearing loss were tested. Amplitude modulation detection and modulation-depth discrimination (MDD) thresholds with sinusoidal carriers of 1 or 5 kHz and modulators in the range from 8 to 256 Hz were used as measures of temporal modulation sensitivity. Speech intelligibility was assessed by obtaining speech reception thresholds in stationary and fluctuating background noise. All thresholds were obtained with and without compression (using a fixed compression ratio of 2:1). RESULTS: For modulation detection, the thresholds were similar or lower for the group with hearing loss than for the group with NH. In contrast, the MDD thresholds were higher for the group with hearing loss than for the group with NH. Fast-acting compression increased the modulation detection thresholds, while no effect of compression on the MDD thresholds was observed. The speech reception thresholds obtained in stationary noise were slightly increased in the compression condition relative to the linear processing condition, whereas no difference in the speech reception thresholds obtained in fluctuating noise was observed. For the group with NH, individual differences in the MDD thresholds could account for 72% of the variability in the speech reception thresholds obtained in stationary noise, whereas the correlation was insignificant for the hearing-loss group. CONCLUSIONS: Fast-acting compression can restore modulation detection thresholds for listeners with hearing loss to the values observed for listeners with NH. Despite this normalization of the modulation detection thresholds, compression does not seem to provide a benefit for speech intelligibility. Furthermore, fast-acting compression may not be able to restore MDD thresholds to the values observed for listeners with NH, suggesting that the two measures of amplitude modulation sensitivity represent different aspects of temporal processing. For listeners with NH, the ability to discriminate modulation depth was highly correlated with speech intelligibility in stationary noise.

Head Shadow and Binaural Squelch for Unilaterally Deaf Cochlear Implantees.

BACKGROUND: Cochlear implants (CIs) can improve speech-in-noise performance for listeners with unilateral sensorineural deafness. But these benefits are modest and in most cases are limited to head-shadow advantages, with little evidence of binaural squelch. HYPOTHESIS: The goal of the investigation was to determine whether CI listeners with normal hearing or moderate hearing loss in the contralateral ear would receive a larger head-shadow benefit for target speech and noise originating from opposite sides of the head, and whether listeners would experience binaural squelch in the free field in a test involving interfering talkers. METHODS: Eleven CI listeners performed a speech-identification task in the presence of interfering noise or speech. Six listeners had single-sided deafness (normal or near-normal audiometric thresholds in the acoustic ear) and five had asymmetric hearing loss (hearing loss in the acoustic ear treated with a hearing aid). Listeners were tested with the acoustic ear only and bilaterally with the CI turned on. One set of conditions examined head-shadow effects with target speech and masking noise presented from azimuths of 0 or ±108 degrees. A second set of conditions examined binaural squelch, with target speech presented from the front and interfering talkers symmetrically placed on both sides. RESULTS: On average, the largest head-shadow benefit (5 dB) occurred when the target and masking noise were presented on opposite sides of the head. Listeners also showed an average of 2 dB of squelch, but only when the target speech was masked by interfering talkers of the same sex as the target. CONCLUSIONS: CIs provide listeners with unilateral deafness important benefits for speech perception in complex spatial environments, including a larger head-shadow benefit when speech and noise originate on opposite sides of the head, and an improved ability to perceptually organize an auditory scene with multiple competing voices.The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army/Navy/Air Force, Department of Defense, or US Government.

Limiar diferencial de mascaramento: valores de referência em adultos / Masking level difference: reference values in adults

RESUMO Introdução O Limiar Diferencial de Mascaramento é um teste comportamental que avalia o mecanismo de interação binaural do processamento auditivo. Objetivo Descrever o Limiar Diferencial de Mascaramento em adultos, a fim de contribuir para o estabelecimento de valores de referência para o teste. Métodos Foram avaliadas 109 mulheres sem queixas auditivas e com audiometria normal. Foi utilizada a versão do Limiar Diferencial de Mascaramento da Auditec of Saint Louis, que consiste na apresentação de 33 segmentos de ruído de banda estreita nas duas orelhas, por pelo menos, três segundos, na presença ou não de tom puro de 500 Hz. Foram utilizadas três condições distintas: tom puro e ruído de banda estreita em fase, nas duas orelhas (condição sinal/ruído homofásica - SoNo); tom puro em fase invertida, em uma das orelhas e o ruído em fase, nas duas orelhas (condição sinal/ruído antifásica - SπNo); ruído sem a presença de tom puro ( no tone – NT). A tarefa para as participantes foi a de indicarem se ouviram ou não o tom. Resultados O valor médio na condição homofásica (SoNo) foi de 12,00 dB, com erro padrão de 0,284 e, na condição antifásica (SπNo), foi de 22,77 dB, com erro padrão de 0,510. O valor médio resultante da diferença entre as duas condições, Limiar Diferencial de Mascaramento, foi de 10,83 dB, com erro padrão de 0,316. Conclusão O Limiar Diferencial de Mascaramento médio, obtido a partir de 109 adultos jovens, normo-ouvintes, do sexo feminino, foi de 10,83 dB.

ABSTRACT Introduction The Masking level difference is a behavioral test that evaluates the mechanism of binaural interaction of auditory processing. Purpose Describe the masking level difference in adults, to contribute to the establishment of reference values for the test. Methods 109 women with normal audiometry and without hearing complaints were evaluated. The version of masking level difference used was Auditec of Saint Louis, which consists in the presentation of 33 segments of narrow-band noise in one ear for at least three seconds whether or not in the presence 500 Hz pure tone. Three different conditions were used: pure tone and narrow-band noise in phase in both ears (homophasic signal/noise condition - SoNo), inverted phase pure tone in one of the ears and noise in phase in both ears (signal/noise condition - SπNo) and noise without the presence of pure tone (no tone - NT). The task for the participants was to indicate if they have heard the tone or not. Results The average value in homophasic condition (SoNo) was 12 dB, with a standard error of 0.284, and in antiphasic condition (SπNo) was 22.77 dB, with standard error of 0.510. The average value resulting from the difference between the two conditions, masking level difference, was 10.83 dB with standard error of 0.316. Conclusion The mean masking level difference obtained from 109 normal hearing young female individuals was 10.83 dB.

Stapedial reflex and recruitment: what is the relationship with tinnitus?

Tinnitus is characterized by an auditory perception of sound, with no stimuli from the external environment. Tinnitus is an increasingly significant complaint, affecting 10-17% of the world population. As a symptom, it should always be considered with pathology in the auditory system. Our study aims to assess the relationship of this symptom with the presence of a stapedial reflex and the phenomenon of recruitment. Medical records of patients complaining of subjective tinnitus during their first consultation in the Outpatient Clinic of the Unicamp Teaching Hospital, in Brazil, between 2011 and 2012 were analyzed. We carried out a study with 65 non-randomized tinnitus individuals using questionnaires, clinical and audiological evaluations. The visual analogue scale was used to characterize the degree of disturbance caused by tinnitus. Statistical tests were performed using the IBM SPSS Statistics 19. No association was found between tinnitus and the presence of acoustic reflex or phenomenon of recruitment. We concluded that there is no relationship between tinnitus, the phenomenon of recruitment or the presence of an acoustic reflex.

Supresión contralateral de otoemisiones acústicas y pruebas audiológicas subjetivas en la detección temprana de hipoacusias no ocupacionales en la adolescencia / Contralateral suppression of otoacoustic emissions and subjective audiological tests in the early detection of non-occupational hearing loss in adolescence

Introducción: Algunas personas presentan una vulnerabilidad especial frente a la exposición excesiva a ruido, provocando una pérdida auditiva inducida por tal estímulo. En la actualidad aún no se conoce en su totalidad el mecanismo subyacente de tal fenómeno y se considera de importancia, dentro del campo de la audiología, indagar sobre el mismo. Una de las formas es profundizar el conocimiento sobre el sistema eferente medial (SEM) y su función protectora ante tales situaciones. El SEM se evalúa de manera indirecta y no invasiva mediante la Supresión Contralateral (SC) de las Otoemisiones AcústicasTransitorias (TEOAEs), constituyendo un estudio relativamente nuevo. Actualmente, tanto su metodología de trabajo como las utilidades y aplicaciones clínicas continúan siendo investigadas y carecen de un consenso de criterios a nivel internacional. La finalidad de esta Tesis Doctoral es conocer las posibles implicancias y aplicaciones clínicas de la SC de las TEOAEs en relación a las pruebas audiológicas subjetivas y el comportamiento de los adolescentes con respecto a la participación enactividades recreativas que suponen exposición a música. Material y Método: La investigación se desarrolló dentro deun Programa de Conservación y Promoción de la Audición en adolescentes implementado en el Centro de Investigación y Transferencia en Acústica (CINTRA), UnidadAsociada del CONICET, de la Universidad Tecnológica Nacional û Regional Córdoba. El estudio se llevó a cabo con un diseño longitudinal, iniciándose en el año 2006 y finalizando en el año 2011.(AU)

SUMMARY: Introduction: Some people show a special vulnerability to excessive exposition to noise, which causes a hearing loss induced by such stimulus. At present, the underlying mechanism of such phenomenon is not completely known and to investigate about this is considered important within the field of audiology. One of the ways to enquire into this problem is to study in depth the medial efferent system (MES) and its protective function in such situations. MES is tested indirectly and in a non-invasive way by means of the Contralateral Suppression (CS) of Transient Evoked Otoacoustic Emissions (TEOAEs), a relatively new study. Currently, its methodologies as well as its clinical applications are being investigated and there is a lack ofconsensus of criteria at the international level. The aim of this Doctoral Thesis is to get to know the possible implications and clinical applications for CS of the TEOAEs related to the subjective hearing tests and the behavior ofadolescents in recreational activities that involve music exposure. Material and Method: The research wasconducted within a Conservation and Promotion of Hearing in Adolescents Program implemented at the Centro deInvestigación y Transferencia en Acústica, CINTRA, an Associated Unit of CONICET of Universidad TecnológicaNacional - Regional Córdoba.(AU)

Supresión contralateral de otoemisiones acústicas y pruebas audiológicas subjetivas en la detección temprana de hipoacusias no ocupacionales en la adolescencia / Contralateral suppression of otoacoustic emissions and subjective audiological tests in the early detection of non-occupational hearing loss in adolescence

Introducción: Algunas personas presentan una vulnerabilidad especial frente a la exposición excesiva a ruido, provocando una pérdida auditiva inducida por tal estímulo. En la actualidad aún no se conoce en su totalidad el mecanismo subyacente de tal fenómeno y se considera de importancia, dentro del campo de la audiología, indagar sobre el mismo. Una de las formas es profundizar el conocimiento sobre el sistema eferente medial (SEM) y su función protectora ante tales situaciones. El SEM se evalúa de manera indirecta y no invasiva mediante la Supresión Contralateral (SC) de las Otoemisiones AcústicasTransitorias (TEOAEs), constituyendo un estudio relativamente nuevo. Actualmente, tanto su metodología de trabajo como las utilidades y aplicaciones clínicas continúan siendo investigadas y carecen de un consenso de criterios a nivel internacional. La finalidad de esta Tesis Doctoral es conocer las posibles implicancias y aplicaciones clínicas de la SC de las TEOAEs en relación a las pruebas audiológicas subjetivas y el comportamiento de los adolescentes con respecto a la participación enactividades recreativas que suponen exposición a música. Material y Método: La investigación se desarrolló dentro deun Programa de Conservación y Promoción de la Audición en adolescentes implementado en el Centro de Investigación y Transferencia en Acústica (CINTRA), UnidadAsociada del CONICET, de la Universidad Tecnológica Nacional – Regional Córdoba. El estudio se llevó a cabo con un diseño longitudinal, iniciándose en el año 2006 y finalizando en el año 2011.

SUMMARY: Introduction: Some people show a special vulnerability to excessive exposition to noise, which causes a hearing loss induced by such stimulus. At present, the underlying mechanism of such phenomenon is not completely known and to investigate about this is considered important within the field of audiology. One of the ways to enquire into this problem is to study in depth the medial efferent system (MES) and its protective function in such situations. MES is tested indirectly and in a non-invasive way by means of the Contralateral Suppression (CS) of Transient Evoked Otoacoustic Emissions (TEOAEs), a relatively new study. Currently, its methodologies as well as its clinical applications are being investigated and there is a lack ofconsensus of criteria at the international level. The aim of this Doctoral Thesis is to get to know the possible implications and clinical applications for CS of the TEOAEs related to the subjective hearing tests and the behavior ofadolescents in recreational activities that involve music exposure. Material and Method: The research wasconducted within a Conservation and Promotion of Hearing in Adolescents Program implemented at the Centro deInvestigación y Transferencia en Acústica, CINTRA, an Associated Unit of CONICET of Universidad TecnológicaNacional - Regional Córdoba.

The effects of energetic and informational masking on The Words-in-Noise Test (WIN).

BACKGROUND: In certain masking paradigms, the masker can have two components, energetic and informational. Energetic masking is the traditional peripheral masking, whereas informational masking involves confusions (uncertainty) between the signal and masker that originate more centrally in the auditory system. Sperry et al (1997) used Northwestern University Auditory Test No. 6 (NU-6) words in multitalker babble to study the differential effects of energetic and informational masking using babble played temporally forward (FB) and backward (BB). The FB and BB are the same except BB is void of the contextual and semantic content cues that are available in FB. It is these informational cues that are thought to fuel informational masking. Sperry et al found 15% better recognition performance (∼3 dB) on BB than on FB, which can be interpreted as the presence of informational masking in the FB condition and not in the BB condition (Dirks and Bower, 1969). The Words-in-Noise Test (WIN) (Wilson, 2003; Wilson and McArdle, 2007) uses NU-6 words as the signal and multitalker babble as the masker, which is a combination of stimuli that potentially could produce informational masking. The WIN presents 5 or 10 words at each of seven signal-to-noise ratios (S/N, SNR) from 24 to 0 dB in 4 dB decrements with the 50% correct point being the metric of interest. The same recordings of the NU-6 words and multitalker babble used by Sperry et al are used in the WIN. PURPOSE: To determine whether informational masking was involved with the WIN. RESEARCH DESIGN: Descriptive, quasi-experimental designs were conducted in three experiments using FB and BB in various paradigms in which FB and BB varied from 4.3 sec concatenated segments to essentially continuous. STUDY SAMPLE: Eighty young adults with normal hearing and 64 older adults with sensorineural hearing losses participated in a series of three experiments. DATA COLLECTION AND ANALYSIS: Experiment 1 compared performance on the normal WIN (FB) with performance on the WIN in which the babble segment with each word was reversed temporally (BB). Experiment 2 examined the effects of continuous FB and BB segments on WIN performance. Experiment 3 replicated the Sperry et al (1997) experiment at 4 and 0 dB S/N using NU-6 words in the FB and BB conditions. RESULTS: Experiment 1-with the WIN paradigm, recognition performances on FB and BB were the same for listeners with normal hearing and listeners with hearing loss, except at the 0 dB S/N with the listeners with normal hearing at which performance was significantly better on BB than FB. Experiment 2-recognition performances on FB and BB were the same at all SNRs for listeners with normal hearing using a slightly modified WIN paradigm. Experiment 3-there was no difference in performances on the FB and BB conditions with either of the two SNRs. CONCLUSIONS: Informational masking was not involved in the WIN paradigm. The Sperry et al results were not replicated, which is thought to be related to the way in which the Sperry et al BB condition was produced.

Intracranial lipomas affecting the cerebellopontine angle and internal auditory canal: a case series.

OBJECTIVE: To assess the long-term outcome of lipomas affecting the cerebellopontine angle (CPA) and internal auditory canal (IAC). PATIENTS: This is a retrospective, single-center study of 10 CPA and IAC lipomas that have presented for the last 6 years. There were 8 male and 2 female patients whose age ranged from 22 to 71 years. These lesions were distributed equally between left and right sides. INTERVENTION: The natural progression, audiovestibular signs and symptoms, imaging characteristics, and management options have been evaluated. MAIN OUTCOME MEASURE: Long-term clinical outcome was correlated with serial imaging and audiograms. RESULTS: The most common presenting feature was hearing loss with an average lesion size of 8 mm. Two patients experienced imbalance, with one requiring operative intervention for incapacitating vertigo. The other 9 were managed conservatively. Follow-up imaging was available for 8 cases, and no growth was observed in any of these, with an average follow-up of 3.5 years. CONCLUSION: Because of the resolution of modern imaging, lipomas of the IAC and CPA are increasingly being recognized and accurately diagnosed. Our data suggest that these lesions are more common than previously thought, representing approximately 1% of all lesions in this location referred to our center. With the absence of growth in 8 cases with follow-up average of 3.5 years as our basis, we recommend that these lesions are managed conservatively by serial imaging. In rare cases, surgery may be required if the lesion is resulting in incapacitating symptoms, such as significant balance disturbance.

Amplitude modulation detection by listeners with unilateral dead regions.

BACKGROUND: A dead region is a region in the cochlea where the inner hair cells and/or neurons are functioning very poorly, if at all. We have shown that, for people with sensorineural hearing loss, thresholds for detecting sinusoidal amplitude modulation (AM) of a sinusoidal carrier were lower for ears with high-frequency dead regions, as diagnosed using the threshold-equalizing noise test, calibrated in hearing level, than for ears without dead regions when the carrier frequency was below the edge frequency, fe, of the dead region. PURPOSE: To measure AM-detection thresholds for subjects with unilateral dead regions, using carrier frequencies both below and above fe. RESEARCH DESIGN: Ten subjects with bilateral high-frequency hearing loss, but with unilateral high-frequency dead regions, were tested. The carriers were presented at sensation levels of 5, 10, or 15 dB. The values of fe were close to 1000, 1500, or 2000 Hz. RESULTS: For carrier frequencies below fe, AM-detection thresholds were lower for the ears with dead regions than forthe ears without dead regions, replicating earlier findings. In contrast, for carrier frequencies above fe, AM-detection thresholds tended to be higher for ears with dead regions than for ears without dead regions. CONCLUSIONS: The reason why AM detection was poorer in the ears with dead regions for carrier frequencies above fe is unclear. However, this finding is consistent with the generally poor discrimination of sounds that has been reported previously for sounds with frequency components falling within a dead region. The results have implications for the ability of people with dead regions to use information from frequency components falling inside the dead region.

Procedimiento para obtener el reclutamiento mediante microfónicos cocleares / A procedure to obtain the recruitment using cochlear microphonic potentials

Objetivo: Aportar un procedimiento objetivo para la obtención del factor de reclutamiento (recruitment). En la actualidad todos los métodos están basados en la respuesta subjetiva del paciente. La relación entre el aumento del potencial microfónico coclear (MC) y el incremento del estímulo es la base de esta aportación. El sistema permite la apreciación de décimas de decibelio, precisión necesaria para determinar el poder diferencial de amplitud auditiva en los pacientes. Método: Se ha empleado un equipo específico para el estudio de los potenciales MC. Hemos comparado los resultados obtenidos con esta nueva técnica con los determinados subjetivamente por el método de Lüscher. Se presenta a 10 adultos sin propósito estadístico. Previamente se comprobó la precisión física del equipo, y luego se practicaron determinaciones en animales de experimentación y, por último, en humanos. Resultados: Obtenemos mediante MC una desviación máxima de 0,3 dB respecto a la apreciación subjetiva de los pacientes. En la repetición de la prueba objetiva se obtienen idénticos resultados en el mismo paciente, mientras que en el estudio subjetivo se observan discrepancias en las repeticiones. Conclusiones: La posibilidad de estudiar el reclutamiento objetivamente abre nuevas perspectivas en diagnóstico precoz y nos capacita para optar más acertadamente respecto a la colocación de un implante o la adaptación de un audífono, con un control automático de volumen correcto unido al ajuste de la ganancia selectiva en frecuencia, ya que obtenemos simultáneamente el perfil audiométrico umbral

Objective: To present an objective procedure for recruitment measure. Nowadays all recruitment methods are based on the patients’ subjective responses. This procedure is based on the ratio between an increase in the cochlear microphonic potential and the increase in stimuli intensity. The system allows recruitment to be measured down to one tenth of a decibel; the precision necessary to differentiate the auditory capacity of patients. Method: We used a specific technique to detect cochlear microphonic potentials. We have compared the results obtained with this new technique with those determined by the Luscher method. We present 10 adults with no statistic aim. We first tested the physical accuracy followed by measures with laboratory animals and humans. Results: We obtained a maximum deviation of 0.3 dB with respect to the patients’ subjective appreciation. During the repetition of the objective measure with the same patients, we obtained identical results, whereas significant differences were observed with the repetitions in the subjective study. Conclusions: The possibility of an objective measurement for recruitment opens up new perspectives for early diagnosis. This technique may be of assistance in the decision to place an implant or how to adapt a hearing aid. Through automatic volume control as well as the correct adjustment of the selective gain in frequency, we can also obtain the threshold audiometric profile simultaneously

Using beamforming and binaural synthesis for the psychoacoustical evaluation of target sources in noise.

The potential of spherical-harmonics beamforming (SHB) techniques for the auralization of target sound sources in a background noise was investigated and contrasted with traditional head-related transfer function (HRTF)-based binaural synthesis. A scaling of SHB was theoretically derived to estimate the free-field pressure at the center of a spherical microphone array and verified by comparing simulated frequency response functions with directly measured ones. The results show that there is good agreement in the frequency range of interest. A listening experiment was conducted to evaluate the auralization method subjectively. A set of ten environmental and product sounds were processed for headphone presentation in three different ways: (1) binaural synthesis using dummy head measurements, (2) the same with background noise, and (3) SHB of the noisy condition in combination with binaural synthesis. Two levels of background noise (62, 72 dB SPL) were used and two independent groups of subjects (N=14) evaluated either the loudness or annoyance of the processed sounds. The results indicate that SHB almost entirely restored the loudness (or annoyance) of the target sounds to unmasked levels, even when presented with background noise, and thus may be a useful tool to psychoacoustically analyze composite sources.

Spectral loudness summation for sequences of short noise bursts.

Recent loudness data of single noise bursts indicate that spectral loudness summation depends on signal duration. To gain insight into the mechanisms underlying this duration effect, loudness was measured as a function of signal bandwidth centered around 2 kHz for sequences of 10-ms noise bursts at various repetition rates and, for comparison, for single noise bursts of either 10- or 1000-ms duration. The test-signal bandwidth was varied from 200 to 6400 Hz. For the repeated noise bursts, the reference signal had a bandwidth of 400 Hz. For the single noise bursts, data were obtained for two reference bandwidths: 400 and 3200 Hz. In agreement with previous results, the magnitude of spectral loudness summation was larger for the 10-ms than for the 1000-ms noise bursts. The reference bandwidth had no significant effect on the results for the single noise bursts. Up to repetition rates of 50 Hz, the magnitude of spectral loudness summation for the sequences of noise bursts was the same as for the single short noise burst. The data indicate that the mechanism underlying the duration effect in spectral loudness is considerably faster than the time constant of about 100 ms commonly associated with the temporal integration of loudness.

Abnormal timing delays in auditory brainstem responses evoked by bilateral cochlear implant use in children.

HYPOTHESIS: A period of unilateral implant use before bilateral implantation affects timing of brainstem processes measured by the electrically evoked auditory brainstem response (EABR). BACKGROUND: EABR latencies decrease with unilateral implant use potentially disrupting binaural timing cues important in auditory brainstem processing of bilateral input. METHODS: EABRs were evoked by electrical pulses from the left, right, and both implants simultaneously in 3 groups of children. All were initially implanted at ages younger than 3 years and had the following: 1) a long delay (>2 yr [n = 16]), 2) a short delay (<1 yr [n = 15]), or 3) no delay (n = 15) between left and right ear implantation. Responses were recorded on the first day of bilateral implant use and 3 and 9 months thereafter. RESULTS: Relative to responses evoked in the experienced ear, the naive ear showed prolonged latency in both the EABR peaks and the binaural difference response. After 3 and 9 months of bilateral implant use, the relative prolongation decreased in the long and short delay groups, but significant differences persisted in the former. No clear differences in latencies evoked by the left versus right implant were found at any time point in children receiving bilateral implants simultaneously. CONCLUSION: Results suggest potential disruptions to binaural brainstem processing based on timing cues in children receiving a second cochlear implant after more than 2 years of unilateral implant use that persist through at least the first 9 months of bilateral implant use.

Detection of the uncomfortable loudness level by electroencephalographic data: a novelty detection approach using habituation correlates.

The objective fitting of hearing aids and cochlear implants in uncooperative patients still remains a challenge. Especially in determining the threshold of uncomfortable loudness which cannot be predicted from the auditory threshold. In this study, we propose a single sweeps processing method which employs a hybrid approach of adaptive frame decomposition adaptation by a tight wavelet frame and the gaussian novelty detection for the detection of large-scale electroencephalographic responses correlates of habituation in late auditory evoked potentials. For this, habituation is discerns as a novel event. It is concluded that the new approach provides a fast and reliable method in the discrimination of uncomfortable loudness level from comfortable loudness level. It can be further use in more clinically oriented studies related to an objective frequency specific fitting of hearing aids or cochlear implants.

Temporal integration and compression near absolute threshold in normal and impaired ears.

The decrease in absolute threshold with increasing stimulus duration (often referred to as "temporal integration") is greater for listeners with normal hearing than for listeners with sensorineural hearing loss. It has been suggested that the difference is related to reduced basilar-membrane (BM) compression in the impaired group. The present experiment tested this hypothesis by comparing temporal integration and BM compression in normal and impaired ears at low levels. Absolute thresholds were measured for 4, 24, and 44 ms pure-tone signals, with frequencies (f(s)) of 2 and 4 kHz. The difference between the absolute thresholds for the 4 and 24 ms signals was used as a measure of temporal integration. Compression near threshold was estimated by measuring the level of a 100 ms off-frequency (0.45f(s)) pure-tone forward masker required to mask a 44 ms pure-tone signal presented at sensation levels of 5 and 10 dB. There was a significant negative correlation between amount of temporal integration and absolute threshold. However, there was no correlation between absolute threshold and compression at low levels; both normal and impaired ears showed a nearly linear response. The results suggest that the differences in integration between normal and impaired ears cannot be explained by differences in BM compression.