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<p> </p><p>I denna studie har jämförelse gjorts mellan Interacoustics Eclipse och GSI Audera i samband med Auditory Steady-State Respons (ASSR) mätningar.</p><p>Syftet med studien var att undersöka ASSR som metod, att utvärdera dess tillförlitlighet i jämfö­relse med tonaudiometri för personer med normal hörsel och personer med hörsel­nedsätt­ning. Avsikten var dessutom att undersöka om elektrod­placering­ på örsnibb eller på mastoid påverkade mät­resultatet, försökspersonens upplevelse av instrumen­­t­ens ljudstimuli, om de estimerade ASSR-värdena påverkades av att mättillfället påbörjades eller avslutades med Interacoustics Eclipse samt undersöka tiden för mätningarna.</p><p>En experimentell studie genomfördes. Mätningarna som utfördes var tonaudiometri och ASSR, den senare uppmättes med Interacoustics Eclipse och GSI Audera på (n=20) vuxna med normal hörsel och (n=4) vuxna med hörselnedsättning.</p><p>För personer med normal hörsel påvisades en god överensstämmelse mellan estimerade ASSR-värden och tonaudiometri för Interacoustics Eclipse, något sämre överensstämmelse för GSI Audera. Genomsnittlig mättid för båda instrumenten var ca 40 min. Resultaten visade att elektrodplaceringen inte har någon påverkan på ASSR-värden för Interacoustics Eclipse. Hälften av försökspersonerna upplevde att Interacoustics Eclipse hade ett behagligare ljudstimuli att slappna av till och den andra hälften upplevde GSI Audera som behagligast. De estimerade ASSR-värdena påverkades minimalt beroende på om mättillfället påbörjades eller avslutades med Interacoustics Eclipse.</p><p> </p>

I denna studie har jämförelse gjorts mellan Interacoustics Eclipse och GSI Audera i samband med Auditory Steady-State Respons (ASSR) mätningar. Syftet med studien var att undersöka ASSR som metod, att utvärdera dess tillförlitlighet i jämfö­relse med tonaudiometri för personer med normal hörsel och personer med hörsel­nedsätt­ning. Avsikten var dessutom att undersöka om elektrod­placering­ på örsnibb eller på mastoid påverkade mät­resultatet, försökspersonens upplevelse av instrumen­­t­ens ljudstimuli, om de estimerade ASSR-värdena påverkades av att mättillfället påbörjades eller avslutades med Interacoustics Eclipse samt undersöka tiden för mätningarna. En experimentell studie genomfördes. Mätningarna som utfördes var tonaudiometri och ASSR, den senare uppmättes med Interacoustics Eclipse och GSI Audera på (n=20) vuxna med normal hörsel och (n=4) vuxna med hörselnedsättning. För personer med normal hörsel påvisades en god överensstämmelse mellan estimerade ASSR-värden och tonaudiometri för Interacoustics Eclipse, något sämre överensstämmelse för GSI Audera. Genomsnittlig mättid för båda instrumenten var ca 40 min. Resultaten visade att elektrodplaceringen inte har någon påverkan på ASSR-värden för Interacoustics Eclipse. Hälften av försökspersonerna upplevde att Interacoustics Eclipse hade ett behagligare ljudstimuli att slappna av till och den andra hälften upplevde GSI Audera som behagligast. De estimerade ASSR-värdena påverkades minimalt beroende på om mättillfället påbörjades eller avslutades med Interacoustics Eclipse.

The current behavioural dead region (DR) diagnosis methods such as psychophysical tuning curves and the threshold-equalising noise test require extensive subject co-operation. These present methods cannot be applied to infants. The work presented in the thesis aimed to develop a fast objective DR diagnosis method that could be applied to sleeping hearing-impaired infants. A novel fast objective electrophysiological method of recording response amplitude curves (RACs) which could enable objective DR diagnosis was developed.RACs were derived by recording auditory steady-state response amplitudes using modulated signals in the presence of narrow-band maskers. Two RAC methods were investigated. In the swept method, RACs were recorded in a single test run by recording the response amplitudes across the frequency range of a continuously swept-frequency narrow-band masker. In the fixed method, response amplitudes of eight separate test runs, each in the presence of differing fixed-frequency narrow-band maskers, were recorded.RACs were recorded in normally hearing adult subjects. The results showed that for normally hearing subjects in condition 1 (swept masker), the mean recorded RAC tip for a 2-kHz signal was 2250 Hz and the repeatability coefficient of two repeated recordings in each subject was 389 Hz; in condition 2 (fixed masker), the respective values were 2251 Hz and 342 Hz. These results indicated that the swept masking method is a viable and fast way to record RACs in normally hearing adults.RACs and psychophysical tuning curves (PTCs) were recorded in hearing-impaired adult subjects in order to asses the tip-frequency agreement between the tests. In some cases there were difficulties in using the required signal and masker levels due to maximum sound level limits. The RACs were poorly shaped and had poor repeatability. These findings indicate that the RAC method that was successfully applied to normally hearing subjects requires further development for use with the hearing impaired. The possible causes for the differences in the accuracy of the method between normally hearing and hearing-impaired subjects are discussed. The work presented in this thesis provides the basis upon which further research can be taken forward. It is envisaged that this work, together with further research, will lead to a clinically-effective objective DR diagnosis method.

Rationale: Schizophrenia patients consistently show deficits in sensory-evoked broadband gamma oscillations and click-evoked entrainment at 40 Hz, called the 40-Hz auditory steady-state response (ASSR). Since such evoked oscillations depend on cortical N-methyl D-aspartic acid (NMDA)-mediated network activity, they can serve as pharmacodynamic biomarkers in the preclinical and clinical development of drug candidates engaging these circuits. However, there are few test-retest reliability data in preclinical species, a prerequisite for within-subject testing paradigms. Objective: We investigated the long-term psychometric stability of these measures in a rodent model. Methods: Female rats with chronic epidural implants were used to record tone- and 40 Hz click-evoked responses at multiple time points and across six sessions, spread over 3 weeks. We assessed reliability using intraclass correlation coefficients (ICC). Separately, we used mixed-effects ANOVA to examine time and session effects. Individual subject variability was determined using the coefficient of variation (CV). Lastly, to illustrate the importance of long-term measure stability for within-subject testing design, we used low to moderate doses of an NMDA antagonist MK801 (0.025–0.15 mg/kg) to disrupt the evoked response. Results: We found that 40-Hz ASSR showed good reliability (ICC=0.60–0.75), while the reliability of tone-evoked gamma ranged from poor to good (0.33–0.67). We noted time but no session effects. Subjects showed a lower variance for ASSR over tone-evoked gamma. Both measures were dose-dependently attenuated by NMDA antagonism. Conclusion: Overall, while both evoked gamma measures use NMDA transmission, 40-Hz ASSR showed superior psychometric properties of higher ICC and lower CV, relative to tone-evoked gamma.

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Orientador: João Candido Fernandes / Banca: Edson Antonio Capello Sousa / Banca: Andrea Cintra Lopes / Resumo: O objetivo desta pesquisa foi determinar os níveis de atenuação de Dispositivos de Proteção Auditivos (DPAs), usando um teste chamado Resposta Auditiva de Estado Estável (RAEE). O teste RAEE é um exame eletrofisiológico que usa elétrodos para captar a atividade elétrica do tronco encefálico, sem depender da resposta do indivíduo, eliminando a subjetividade, assim como aspectos ligados à atenção, tempo de resposta, níveis de audição, etc. Neste método foram avaliados dez indivíduos, por meio da RAEE, estimulando-se o sistema de audição, primeiro sem protetor e, subsequentemente, com dois tipos de protetores auditivos, a saber um de inserção intra-auricular outro circunauricular de uso comum no mercado. Os resultados evidenciaram valores inferiores àqueles expressos no Certificado de Aprovação: para o plug, uma diferença de 10,3 dB, e para a concha, 4,3 dB. Na repetição dos testes, encontrou-se uma boa repetitividade, com diferença entre zero e 5 dB para 75% das frequências testadas. / Abstract: The purpose of this research was to determine the levels of attenuation of Hearing Protection Devices (HPDs) using a test called Auditory Steady-State Response (ASSR). The ASSR test is an electrophysiological examination that uses electrodes to capture the electrical activity of the auditory nerve and the brainstem without depending on the individual's response, thus eliminating the subjectivity of personal factors such as attention, response time, hearing ability, etc. This paper presents the results of a ten test which evaluated the hearing threshold of individuals, by first stimulating the hearing system without a protector and subsequently with a hearing protector. The results of this study were lower than those expressed in the Certificate of Approval: to plug a gap of 10.3 dB and dB the ear mufflers. The repetition of tests found a good repeatability with a difference between zero and 5 dB for 75% of the frequencies tested. / Mestre

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