[Truncated abstract] The mammalian cochlea receives an efferent innervation which originates in the superior olive. Known collectively as the olivocochlear system, this efferent innervation can be divided into lateral and medial systems. While the function of the lateral efferent system in the cochlea is still unknown, previous studies have identified both excitatory and inhibitory changes in sound-evoked and spontaneous cochlear responses attributable to the lateral efferent system. One of the neurotransmitters in the lateral efferents is the catecholamine dopamine, which in the central nervous system is known to exert inhibitory and excitatory effects by activating different receptor subtypes. The first experiments in this thesis were designed to determine if activation or blockade of different dopamine receptor subtypes in the cochlea could lead to both excitatory and inhibitory changes in sound-evoked and spontaneous cochlear responses. Adult guinea pigs were anaesthetised (Nembutal and Hypnorm) and highly specific D1/5 (SKF 38393, SKF 81297, SCH 23390), D2 ((+) PHNO, L 741, 626) and D3 (PD 128907, U 99194A) receptor agonists and antagonists were perfused through the cochlea for 15 minutes. Sound-evoked (compound action potential, summating potential, cochlear microphonic) and spontaneous cochlear responses were recorded before and after perfusion. Remarkably, activating or blocking D1/5 or D2 receptor subtypes resulted in the suppression of CAP amplitudes. These findings are paradoxical as the agonist data suggest that the D1/5 and D2 receptor subtypes are inhibitory, but the antagonist perfusions suggest that these receptors are excitatory. We propose that the presence of an agonist induces a process of receptor desensitisation which would elicit changes akin to receptor antagonism. If this is indeed the case then our agonist findings are spurious and require further interpretation. ... The suppression of the cochlear microphonic suggests that dopamine receptor influence is not confined to the primary afferent dendrite may also include the active process of the outer hair cells. The D1/5 and D2 antagonist data also suggests that dopamine receptors are activated by intrinsic dopamine. Therefore, we attempted to investigate the effects of putative dopamine depletion of the cochlea and found that application of the dopaminergic neurotoxin MPTP causes changes in both neural and hair cell responses which have not been reported before. However, we also demonstrated that tyrosine hydroxylase positive nerve fibres are still present in MPTP treated cochleae which suggests that dopamine is still present in these cochleae. Furthermore, we observed significant electrophysiological changes in these same cochleae when these were exposed to a D2 receptor antagonist which again supports the presence of intrinsic dopamine in these 'depleted cochleae'. These data suggest that the currently accepted method of acute dopamine depletion using MPTP is insufficient and different methods must be developed in the future.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 179-220) Also available in print.

Thesis (Au. D.)--Missouri State University, 2008. / "May 2008." Includes bibliographical references (leaves 76-86). Also available online.

Thesis (Au. D.)--Missouri State University, 2008. / "May 2008." Includes bibliographical references (leaves 76-86). Also available online.

Orientador: Ana Cláudia Figueiredo Frizzo / Banca: Liliane Desgualdo Pereira / Banca: Vitor Engrácia Valenti / Resumo: Introdução: Os potenciais corticais auditivos e a variabilidade da frequência cardíaca são temas amplamente estudados na literatura nacional e internacional. Embora sejam escassos estudos que relacionam esses dois parâmetros de avaliação do sistema nervoso. Objetivo: Analisar a associação entre os potenciais corticais auditivos e a modulação autonômica cardíaca frente a diferentes estímulos acústicos. Métodos: Participaram desta pesquisa 60 mulheres saudáveis, com idade entre 18 e 25 anos. Os critérios de inclusão foram: ausência de distúrbios cardiorrespiratórios, cognitivos, psiquiátricos, neurológicos e tratamento medicamentoso que influencie a regulação autonômica cardíaca; indivíduos que não ingeriram bebidas alcoólicas em excesso nas últimas 24 horas e que deixaram de ser tabagistas há pelo menos um ano; audiometria tonal liminar com resultados normais e imitânciometria com curva tipo A e reflexos ipsi e contralaterais presentes. Antes do exame do Potencial cortical, foram mensuradas a pressão arterial e a frequência cardíaca em repouso com auxílio de estetoscópio e esfigmomanômetro e do cardiofrequencímetro Polar RS800CX. Após a coleta dessas medidas, foi iniciado o exame do potencial cortical simultaneamente com a coleta da variabilidade da frequência cardíaca. Os índices lineares nos domínios do tempo e da frequência foram analisados através do software Kubios HRV analysis - versão 2,0. A análise estatística descritiva foi analisada por meio da média e desvio padrão, ao passo que para a análise inferencial foram aplicados os seguintes testes: teste de correlação de Pearson para distribuições paramétricas e de Spearman para distribuições nãoparamétricas. Resultados: Foram observadas correlações entre os potenciais corticais auditivos e os índices da ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Introduction: The auditory cortical potentials and heart rate variability are widely studied topics in the national and international literature. Although few studies associating these two endpoints of the nervous system. Objective: To analyze the association between auditory cortical potentials and cardiac autonomic modulation due to different acoustic stimuli. Methods: We analyzed 60 healthy women, aged between 18 and 25 years. Inclusion criteria were: absence of cardiorespiratory disorders, cognitive, psychiatric, neurological and medical treatment to influence the cardiac autonomic regulation; individuals who did not drink alcohol in excess in the last 24 hours and no longer in smokers for at least one year; pure tone audiometry and impedance tests with normal results with type A curve and ipsilateral and contralateral reflexes present. Before examining the cortical potential, were measured blood pressure and heart rate at rest with stethoscope and sphygmomanometer aid and heart rate monitor Polar RS800CX. After collecting these measures, started the examination of cortical potential while the collection of heart rate variability. Linear indices in the field of time and frequency were analyzed using the Kubios HRV analysis software - version 2.0. Descriptive statistical analysis was analyzed by mean and standard deviation, whereas for the inferential analysis the following tests were applied: Pearson correlation test for parametric and Spearman distributions to non-parametric distributions. Results: Correlations were observed between the auditory cortical potentials and indexes of heart rate variability. When analyzed in the time domain, SDNN index correlated with the P3a latency and amplitude of P2, and P3a; the RMSSD index correlated with the latencies of N1, P2, N2 and amplitudes of P3a and MLM and ... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2015-07-22T20:50:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-01-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Introdução: A necessidade da realização de diagnóstico audiológico nas primeiras semanas ou meses de vida aumentou com a consolidação dos programas de triagem auditiva neonatal. As emissões otoacústicas (EOA) e o potencial evocado auditivo de tronco encefálico (PEATE) com estímulo clique são amplamente utilizados. Para que a intervenção precoce tenha sucesso, informações precisas quanto ao tipo, grau e configuração da perda auditiva tornam-se necessárias. A realização do PEATE com o estímulo tone burst (TB) e da pesquisa da resposta auditiva de estado estável (RAEE) vêm se mostrando de grande valia, já que tais testes fornecem informações específicas por freqüência, permitindo uma avaliação audiológica mais detalhada. Objetivo: Analisar a aplicabilidade clínica do PEATE TB e da RAEE em 2 kHz, em lactentes nascidos a termo e pré-termo. Método: A casuística foi composta por 17 lactentes pré-termo e 19 lactentes a termo, de ambos os gêneros. O estudo foi realizado na UNIFESP e os lactentes, em sono natural, foram submetidos ao PEATE TB e à RAEE na freqüência de 2000 Hz, utilizando-se o equipamento Smart EP da Intelligent Hearing Systems. Resultados: A comparação entre as respostas da orelha direita e esquerda não apresentou diferenças estatisticamente significantes, permitindo considerar a amostra como um todo. A comparação das respostas dos lactentes pré-termo e a termo não apresentou diferenças estatisticamente significantes, com exceção do tempo de duração da RAEE. As latências médias da onda V no PEATE TB foram de 7,9 ms a 80 dBnNA, 8,9 ms a 60 dBnNA, 9,9 ms a 40 dBnNA e 10,8 ms a 30 dBnNA. A resposta eletrofisiológica mínima obtida com o PEATE TB foi de 32,4 dBnNA (52,4 dBNPS), em média. A RAEE mínima obtida foi de 13,8 dBNA (26,4 dBNPS), em média. A duração média do PEATE TB foi de 21,1 min e da RAEE de 22 min. Conclusões: O PEATE TB e a RAEE têm aplicabilidade clínica na freqüência de 2 kHz em lactentes, não havendo diferenças entre indivíduos a termo e pré-termo. / Introduction: Audiological diagnosis in the first weeks or months of life has increased with the consolidation of newborn hearing screening programs. Otoacoustic emissions (OAE) and auditory brainstem response (ABR) with click stimuli are widely used for this purpose. For a successful early intervention, accurate information about type, degree, and configuration of hearing loss are necessary. ABR with tone burst stimuli (TB ABR) and auditory steady-state response (ASSR) exams have been of great value, since these tests provide specific frequency information, resulting in a more detailed hearing evaluation. Objective: Analyze the clinical applicability of TB ABR and ASSR at 2 kHz, in full-term and premature infants. Method: The study was conducted at UNIFESP. Subjects were consisted of 17 premature infants and 19 full-term infants, male and female. In natural sleep, they have undergone TB ABR and ASSR exams (Smart EP - Intelligent Hearing Systems), at 2000 Hz. Results: Right and left ears responses showed no statistically significant differences, therefore they were considered as a whole. Wave V mean latencies in TB ABR were 7.9 ms to 80 dBnHL, 8.9 ms to 60 dBnHL, 9.9 ms to 40 dBnHL and 10.8 ms to 30 dBnHL. Electrophysiological minimum response obtained with TB ABR was 32.4 dBnHL (52.4 dBSPL), on average. ASSR minimum response was 13.8 dBHL (26.4 dBSPL), on average. TB ABR and ASSR exams lasted 21.1 min and 22 min, respectively. Premature and full-term infants responses showed no statistically significant differences, except for ASSR duration. Conclusions: Both TB ABR and ASSR have clinical applicability at 2 kHz in infants, with no differences between premature and full-term individuals. / TEDE / BV UNIFESP: Teses e dissertações

Made available in DSpace on 2016-03-07T19:20:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-11-16. Added 1 bitstream(s) on 2016-03-07T19:24:26Z : No. of bitstreams: 1 000858904.pdf: 2531633 bytes, checksum: 4551b73aba444c4c6ff7fc36ac3cf544 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Introdução: Os potenciais corticais auditivos e a variabilidade da frequência cardíaca são temas amplamente estudados na literatura nacional e internacional. Embora sejam escassos estudos que relacionam esses dois parâmetros de avaliação do sistema nervoso. Objetivo: Analisar a associação entre os potenciais corticais auditivos e a modulação autonômica cardíaca frente a diferentes estímulos acústicos. Métodos: Participaram desta pesquisa 60 mulheres saudáveis, com idade entre 18 e 25 anos. Os critérios de inclusão foram: ausência de distúrbios cardiorrespiratórios, cognitivos, psiquiátricos, neurológicos e tratamento medicamentoso que influencie a regulação autonômica cardíaca; indivíduos que não ingeriram bebidas alcoólicas em excesso nas últimas 24 horas e que deixaram de ser tabagistas há pelo menos um ano; audiometria tonal liminar com resultados normais e imitânciometria com curva tipo A e reflexos ipsi e contralaterais presentes. Antes do exame do Potencial cortical, foram mensuradas a pressão arterial e a frequência cardíaca em repouso com auxílio de estetoscópio e esfigmomanômetro e do cardiofrequencímetro Polar RS800CX. Após a coleta dessas medidas, foi iniciado o exame do potencial cortical simultaneamente com a coleta da variabilidade da frequência cardíaca. Os índices lineares nos domínios do tempo e da frequência foram analisados através do software Kubios HRV analysis - versão 2,0. A análise estatística descritiva foi analisada por meio da média e desvio padrão, ao passo que para a análise inferencial foram aplicados os seguintes testes: teste de correlação de Pearson para distribuições paramétricas e de Spearman para distribuições nãoparamétricas. Resultados: Foram observadas correlações entre os potenciais corticais auditivos e os índices da variabilidade da frequência cardíaca. Quando analisados no domínio do tempo, o índice SDNN correlacionou com a latência... / Introduction: The auditory cortical potentials and heart rate variability are widely studied topics in the national and international literature. Although few studies associating these two endpoints of the nervous system. Objective: To analyze the association between auditory cortical potentials and cardiac autonomic modulation due to different acoustic stimuli. Methods: We analyzed 60 healthy women, aged between 18 and 25 years. Inclusion criteria were: absence of cardiorespiratory disorders, cognitive, psychiatric, neurological and medical treatment to influence the cardiac autonomic regulation; individuals who did not drink alcohol in excess in the last 24 hours and no longer in smokers for at least one year; pure tone audiometry and impedance tests with normal results with type A curve and ipsilateral and contralateral reflexes present. Before examining the cortical potential, were measured blood pressure and heart rate at rest with stethoscope and sphygmomanometer aid and heart rate monitor Polar RS800CX. After collecting these measures, started the examination of cortical potential while the collection of heart rate variability. Linear indices in the field of time and frequency were analyzed using the Kubios HRV analysis software - version 2.0. Descriptive statistical analysis was analyzed by mean and standard deviation, whereas for the inferential analysis the following tests were applied: Pearson correlation test for parametric and Spearman distributions to non-parametric distributions. Results: Correlations were observed between the auditory cortical potentials and indexes of heart rate variability. When analyzed in the time domain, SDNN index correlated with the P3a latency and amplitude of P2, and P3a; the RMSSD index correlated with the latencies of N1, P2, N2 and amplitudes of P3a and MLM and interamplitude of N2-P3a; pNN50 index correlated with the latencies of N1 and P2 and with the amplitudes of P3a and MLM and...

Made available in DSpace on 2015-05-14T16:53:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-09-29Bitstream added on 2015-05-14T16:59:32Z : No. of bitstreams: 1 000824110.pdf: 554350 bytes, checksum: 9c0b2908c3d24487eea0470c66d6d425 (MD5) / A audição é um dos principais pontos do processo de comunicação com o meio ambiente tanto de seres humanos quanto de animais. O potencial evocado auditivo de tronco encefálico (BAEP-Brainstem Auditory Evoked Potential) é um método que tem sido utilizado em seres humanos, cães, gatos, bovinos e equinos com a finalidade de identificar possíveis alterações auditivas que não podem ser diagnosticadas durante o exame físico. O BAEP avalia a integridade das vias auditivas, desde a cóclea até o tronco encefálico e permite a identificação de animais com surdez neurossensorial e condutiva. Apesar da importância do BAEP, não foi encontrado nenhum estudo de padronização do seu uso em equinos no Brasil. Dessa maneira, o objetivo deste trabalho foi padronizar a metodologia para obtenção de registros que permitam verificar a latência das ondas obtidas no exame para essa espécie. Foram utilizados 21 equinos adultos, machos e fêmeas, sem histórico prévio de alterações auditivas. Para realização do teste, os animais foram sedados com cloridrato de detomidina. Foram identificadas as latências das ondas I, II, III, IV e V, bem como dos intervalos I-III, III-V e I-V. As médias das latências das ondas foram, onda I 2,4 ms; onda II 2,74 ms; onda III 3,61 ms; onda IV 4,61 ms e onda V 5,49 ms . As médias das latências dos interpicos foram I-III 1,37 ms; III-V 1,88 ms e I-V 3,26 ms. A descrição da metodologia utilizada e a disponibilização dos registros e das latências obtidas podem servir de referência para estudos realizados nessa espécie / Hearing is one of the main points of the communication process with the environment both humans and animals. The Auditory brainstem response (BAEP Brainstem Auditory-Evoked Potential) is a method that has been used in humans, dogs, cats, cattle and horses in order to identify possible hearing impairment that can’t be diagnosed during physical examination . The BAEP evaluates the integrity of the auditory pathway from the cochlea to the brainstem and allows the identification of animals with sensorineural and conductive deafness. Despite the importance of BAEP, no study to standardize its use in horses in Brazil was found. Thus, the objective of this study was to standardize the methodology for obtaining records to verify the wave latencies obtained in the examination for this species. 21 adult horses, males and females were used without previous history of hearing disorders. To perform the test, the animals were sedated with detomidine hydrochloride. Latencies of waves I, II, III, IV and V, as well as the intervals I-III, III-V and IV were identified. The mean latencies of the waves were, I wave 2.4 ms; wave II 2.74 ms ; wave III 3.61 ms; wave IV 4.61 ms and wave V 5.49 ms. The mean latencies of interpeaks were I-III 1.37; III-V 1.88 and I-V 3.26. The description of the methodology used and the availability of records and latencies can serve as a reference for studies in this species

Electrical Impedance Tomography (EIT) is a technique for imaging the spatial distribution of conductivity inside a body using the boundary voltages, in response to applied current patterns, to reconstruct an image. Even though EIT has been proved useful in several medical applications such as mechanical respiration and ventilation monitoring of the lungs, its reported success in localising cerebral conductivity changes due to brain stimulation is very scant. In the case of the human head, the amplitude of the brain response to stimulation is usually very small and gets contaminated with physiological noise initiated from inside the cranium or the scalp. Three types of evoked responses were experimentally investigated: auditory startle response (ASR), CO2 reactivity response, and transient hyperaemic response (THR). ASR is expected to be a result of the brain’s functioning processes. However, the responses to CO2 and THR are expected to be due to cerebral blood volume or flow, due to physiological intervention in blood supply. According to the results, even when the amplitude of EIT measurements shows profound variation as in the case of CO2 reactivation, those could not be physiologically linked to the targeted responses and have been shown to be initiated from the scalp. The consistency of the measurements in the case of CO2 reactivation response was poor (37.50-50%). Meanwhile in the case of THR, although the magnitude of conductivity changes was overall 50% smaller than the previous cases, the subject movement was not necessary. This could be a reason that the consistency of THR case was very good (87%), and this can emphasize the necessity to maintain the changes in the scalp at minimum levels. In the case of ASR the response magnitude was very small (six times smaller than the CO2 reactivity case), and the evoked response can be detected with only 50% consistency. To measure very small EIT signals (such as those expected due to brain function) effectively, one must improve the sensitivity of the measurements to conductivity changes by increasing the excitation current. The functional EIT for Evoked Response (fEITER) system used in our investigations was modified from its initial configuration to increase its excitation current from 1 mApk-pk to 2 mApk-pk or 1 mArms. The bit-truncation in the process of Phase-Sensitive Detection (PSD) has also been improved, to modify the original 16-bit data readout to be 24-bit data readout. These improvements have doubled the instrument’s sensitivity, and have substantially reduced the truncation error to about 183 times. The quality of the physiological waveform was also significantly improved. Therefore, one could study more effectively very fast brain response using the modified system. For example, the latency of responses can be more precisely extracted, or the monitoring of the conductivity change in a period of only a few tens of milliseconds is then possible. The reconstruction of brain images corresponding to these physiologically evoked responses has been the ultimate goal of this thesis. To ensure obtaining the correct images, some crucial issues regarding EIT reconstruction were firstly investigated. One of these issues concerns the modelling error of the numerical head models. The reconstruction requires an accurate model capturing the geometry of the subject’s head with electrodes attached and accurate in-vivo tissue conductivities. However, since it is usually impractical to have a personalised model for each subject, many different head models (including a subject model) were constructed and investigated, to evaluate the possibility of using a generic model for all subjects. The electrode geometry was also carefully included into the models to minimise error. Another issue concerns the appropriate reconstruction algorithm. A novel nonlinear reconstruction method, based on the difference imaging approach and Generalized Minimal Residual method (GMRes) algorithm, with optimal parameters and prior information, was proposed to deal with significant modelling errors. With this algorithm, the experimental results showed that it is possible to use a generic model for reconstructing an impedance change, but the magnitude of the change should be rather small. The last issue tackled was regarding the a priori choice of model parameters, and in particular the tissue conductivities. The tissue conductivities of the scalp and the skull were also estimated by a proposed methodology based on the Gauss-Newton method. The estimation showed that, compared to previous reported values, the conductivity of the scalp was higher, at 0.58 S/m, and that of the skull lower, at 0.008 S/m. Eventually, by exploiting the hardware and firmware advances in the measuring instrument in conjunction with the proposed modelling and reconstruction algorithm, processing our experimental EIT data captured on human heads and a head-like tank confirm that the localisation and imaging of conductivity changes occurring within the head is indeed possible. From the low quality measurements in the case of the CO2 reactivity response, the reconstructed images of this response do not reflect the true conductivity change. The consistency of the images to localise the sources of the changes was very poor (0-50%), i.e. the conductivity changing locations in the images were likely to be random. Our analysis suggests that the changes inside the cranium are likely to be due to the large change in the scalp. In the case of THR, the reconstructed images were able to localise the response in a similar manner to what had been found on the measurements, and the consistency was quite high (76%). Meanwhile, in the case of ASR, surprisingly the consistency of the images was 82%, much higher than the consistency of the measurements, which was only 50%. This was because the changing amplitude of the measurements was too small to be noticed by visualisation, and it was practically cumbersome to investigate all measurements. This statistic confirms that image reconstruction can reveal information that is not directly apparent by observing the measurements. In summary, EIT can be used in brain (function) imaging applications to some extent. The targeted response, which typically originates from inside the cranium is always infused with neurophysiological noise or physical noise at the scalp, and the amplitude of noise determines the possibility to localise the changes. It is also necessary for the desired response to have sufficiently large amplitude. These results show that EIT has been successful in THR and ASR, but for CO2 reactivity response, EIT lacks the necessary sensitivity.

Made available in DSpace on 2016-06-07T17:12:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-02-26. Added 1 bitstream(s) on 2016-06-07T17:16:40Z : No. of bitstreams: 1 000866228.pdf: 2025216 bytes, checksum: 03649865923809ae8153c9989f57557f (MD5) / Introdução: A avaliação auditiva em neonatos é realizada atualmente por testes objetivos, como as emissões otoacústicas e o potencial evocado auditivo de tronco encefálico (PEATE), porém, a principal limitação desses métodos de avaliação é a de não fornecer informações precisas sobre os limiares auditivos por frequência específica, especialmente nas graves. A resposta auditiva de estado estável (RAEE) é uma técnica complementar às existentes, para o diagnóstico da surdez na população pediátrica, sendo sua principal vantagem a de predizer, de forma objetiva e automática, os limiares auditivos por frequência específica. Objetivo: Verificar se há concordância entre os exames PEATE e RAEE na avaliação do limiar auditivo em lactentes. Metodologia: Estudo observacional analítico prospectivo. Critérios de inclusão: lactentes nascidos no local do estudo, com indicadores de risco para a deficiência auditiva e que realizaram os testes PEATE e RAEE na mesma sessão. Variáveis estudadas: dados pessoais, indicadores de risco para a deficiência auditiva e os achados dos exames de PEATE e RAEE. As comparações foram consideradas significativas para p<0,05. Resultados: Atenderam aos critérios de inclusão 66 neonatos, sendo 47% deles do sexo masculino (n=31), idade mediana de 1,2 meses, idade gestacional média de 31 semanas, peso médio ao nascimento 1601g. Treze neonatos tiveram PEATE alterado (20%), sendo que dez deles tinham mais de um indicador de risco acumulado. Os pontos de maior sensibilidade e especificidade na RAEE para as frequências de 500, 1000, 2000 e 4000Hz na orelha direita foram, respectivamente, 47,5; 62,5; 42,5 e 37,5 e na orelha esquerda 65; 45; 55 e 52,5. Conclusão: Houve concordância entre o PEATE e a RAEE em lactentes de risco para deficiência auditiva, sendo possível diferenciar os ouvintes daqueles com deficiência auditiva. Palavras-chave: audição, eletrofisiologia, indicador de risco,... / Introduction: The hearing assessment in neonates is currently done by objective tests, such as otoacoustic emissions and the brainstem auditory evoked potential (BAEP), however the main limitation of these assessment methods it is not to provide accurate information on the hearing threshold by specific frequencies, especially in low frequencies. Auditory steady-state response (ASSR) is a complementary technique to the ones existing for the deafness diagnosis in children and its main advantage is to, objectively and automatically predict the hearing thresholds by specific frequency. Objective: To verify if there is concordance between the BAEP and ASSR tests in the infants hearing threshold assessment. Methods: Prospective analytical study. Comprisal criterion: born infants in the study site, with risk indicators for hearing loss and who were submitted to ABR and ASSR tests in the same session. Variants studied: personal data, risks indicators for hearing loss and findings of BAEP and ASSR tests. Comparisons were considered significant for p <0.05. Results: 66 neonates were included, 47% were male (n = 31), median age of 1.2 months, mean gestational age of 31 weeks and mean birth weight 1601g. Thirteen infants had abnormal BAEP (20%), and ten of them had accumulated more than one risk indicator. Higher sensitivity and specificity points in the ASSR for the frequencies of 500, 1000, 2000 and 4000 Hz in the right ear were, respectively, 47.5; 62.5; 42.5 and 37.5 and the left ear 65; 45; 55 and 52.5. Conclusion: There was concordance between the ABR and ASSR tests in infants with risk for hearing loss, being possible to distinguish who have normal hearing from those with hearing loss