Submitted by LETICIA SAMPAIO DE OLIVEIRA null (leticiaoliveira.fono@gmail.com) on 2018-04-03T00:30:19Z No. of bitstreams: 1 VERSÃO FINAL LETICIA02.04corrigidoAna.pdf: 2556490 bytes, checksum: e05d6bcf4061674f653b1dfb15b7474b (MD5) / Approved for entry into archive by Satie Tagara (satie@marilia.unesp.br) on 2018-04-03T14:21:29Z (GMT) No. of bitstreams: 1 oliveira_ls_me_mar.pdf: 2556490 bytes, checksum: e05d6bcf4061674f653b1dfb15b7474b (MD5) / Made available in DSpace on 2018-04-03T14:21:29Z (GMT). No. of bitstreams: 1 oliveira_ls_me_mar.pdf: 2556490 bytes, checksum: e05d6bcf4061674f653b1dfb15b7474b (MD5) Previous issue date: 2018-03-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Introdução: Os dois primeiros anos de vida de um indivíduo são os mais significativos para o desenvolvimento de habilidades auditivas e de linguagem. A neuroplasticidade durante esse período é máxima e o córtex mais responsivo, podendo realizar mais reorganizações neurais. Porém, caso o indivíduo sofra algum tipo de privação sensorial, oriunda de perdas auditivas sensorioneurais ou condutivas, durante a infância, o desenvolvimento das estruturas da via auditiva periférica e central será afetado, e trará consequências para o processamento binaural. O BIC pode trazer evidências em relação à binauralidade, pois a resposta evocada por um estímulo bilateral gera respostas mais específicas em relação ás estruturas responsáveis pelo processamento binaural, tornando sua análise mais confiável. Objetivo: Caracterizar as respostas auditivas corticais do Potencial Evocado Auditivo Cortical com estímulos de fala por estimulação monoaural e bilateral e analisar o BIC em neonatos e crianças sem e com histórico de otite de repetição. Metodologia: A pesquisa foi desenvolvida no Setor de Audiologia do Centro de Estudos da Educação e da Saúde (CEES), da Faculdade de Filosofia e Ciências, Universidade Estadual Paulista (UNESP), Campus de Marília, São Paulo. Foram selecionados sujeitos de zero a oito anos e 11 meses, em boas condições de saúde geral, de ambos os gêneros, divididos em grupo um (normalidade) e grupo dois (histórico de infecção auditiva), e entre eles divididos em subgrupos a partir da faixa etária. O procedimento de coleta foi o PEAC com estímulo de fala /ba/-/da/ em paradigma oddball. O resultado do complexo de ondas P1-N1-P2-N2-P3 foi avaliado pela pesquisadora e dois juízes experientes na área de eletrofisiologia. Foi realizado o cálculo aritmético dos 512 pontos da onda a fim de obter a grande média das ondas dos sujeitos de ambos os grupos. Foram realizados os testes estatísticos: Shapiro-wilk e Ancova de Medidas Repetidas Mista para analisar o efeito do grupo, da condição e da interação (grupo VS condição) controlando o efeito da co-variável idade e sexo. Resultados: Houve diferença significativa entre os grupos para todos os valores de latência, sendo que para as latências dos potenciais P1, N1, P2 e N2 as diferenças entre os grupos ocorreram nas três condições analisadas (OE, OD e binaural), demonstrando influência da privação sensorial. Para a latência do potencial P3 foi observado diferença entre os grupos somente para a OD e binaural. Não houve diferenças significativas em relação às amplitudes das ondas. Conclusão: Existem diferenças no PEAC com estímulos de fala e no componente de interação binaural de crianças com e sem privação sensorial. / Introduction: The first two years of an individual's life are the most significant for the development of auditory and language skills. Neuroplasticity during this period is maximal and the cortex more responsive, being able to perform more neural reorganizations. However, if the individual experiences some kind of sensory deprivation, due to sensorineural or conductive hearing loss, during childhood, the development of peripheral and central auditory pathway structures will be affected, and will have consequences for binaural processing. The BIC can bring evidence regarding binaurality, since the response evoked by a bilateral stimulus generates morespecific responses to the structures responsible for binaural processing, making its analysis more reliable. Objective: To characterize the development of monaural and binaural auditory function in infants and children with and without history of sensory deprivation through Cortical Auditory Evoked Potential (CAEP). Methodology: The research was developed in the Audiology Sector of the “Centro de Estudos em Educação e Saúde” (CEES), Faculty of Philosophy and Sciences, State University of São Paulo (UNESP),Campus of Marília, São PauloState. Subjects from 0 to 8 years and 11 months, in good general health, were selected from both genders, divided into group 1 (normality) and group 2 (history of auditory infection), and divided into subgroups from age group.The collection procedure was the CAEP with speech stimulus /ba / -/da/ in the oddball paradigm. The results of the P1-N1-P2-N2-P3 wave complex were evaluated by the researcher and two experienced judges in the field of electrophysiology. The arithmetic calculation of the 512 wave points was performed in order to obtain the large wave mean of the subjects of both groups. Statistical tests were performed: Shapiro-wilk and Ancova of Mixed Repeated Measures to analyze the effect of group, condition and interaction (group vs. condition) controlling the effect of co-variable age and sex. Results: There was a significant difference between the groups for all latency values, and for the latencies of the potential P1, N1, P2 and N2 the differences between the groups occurred in the three analyzed conditions (OE, OD and binaural) demonstrating the influence of sensorial deprivation. For the latency of the P3 potential, there was a difference between the groups only for the OD and binaural. There were no significant differences in relation to the wave amplitudes. Conclusion:There are differences in the binaural auditory development of children with and without sensory deprivation ascertained by the results of the CAEP with speech stimulus.

Introdução: O implante coclear (IC) amplamente aceito como forma de intervenção e (re) habilitação nas perdas auditivas severas e profundas nas diversas faixas etárias. Contudo observa-se no usuário do IC unilateral queixas como localização e compreensão sonora em meio ao ruído, gerado pelo padrão anormal de estimulação sensorial. A fim de fornecer os benefícios da audição binaural, é preconizado a estimulação bilateral, seja por meio do IC bilateral ou com a adaptação de um aparelho de amplificação sonora individual (AASI) contralateralmente ao IC. Esta última condição é referida como estimulação bimodal, quando temos, concomitantemente dois modos de estimulação: Elétrica (IC) e acústica (AASI). Não há dados suficientes na literatura voltados à população infantil que esclareça ou demonstre o desenvolvimento do córtex auditivo na audição bimodal. Ressalta-se que não foram encontrados estudos em crianças. Objetivo: Caracterizar o PEAC complexo P1, N1 P2 em usuários da estimulação bimodal e verificar se há correlação com testes de percepção de fala. Metodologia: Estudo descritivo de séries de casos, com a realização do PEAC em cinco crianças usuárias da estimulação bimodal, a partir da metodologia proposta por Ventura (2008) utilizando o sistema Smart EP USB Jr da Intelligent Hearing Systems. Foi utilizado o som de fala /da/, apresentado em campo livre. O exame será realizado em três situações: Somente IC, IC e AASI e somente AASI. A análise dos dados dos potenciais corticais foi realizada após a marcação da presença ou ausência dos componentes do complexo P1-N1-P2 por dois juízes com experiência em potenciais evocados. Resultados: Foi obtida a captação do PEAC em todas as crianças em todas as situações de teste, além do que foi possível observar a correlação destes com os testes de percepção auditiva da fala. Foi possível verificar que o registro dos PEAC é um procedimento viável para a avaliação da criança com estimulação bimodal, porém, ainda não há dados suficientes quanto a utilização deste para a avaliação e indicação do IC bilateral. / Introduction: The cochlear implant (CI) is already accepted in the area, as an intervention (re)habilitation in severe and profound hearing loss in different age groups. However, it is observed in the unilateral CI users have complaints such as sound localization and understanding speech in noise. Recent studies with Cortical Auditory Evoked Potential (CAEP) demonstrated the fact that the CI cannot favors the ipsilateral development of the auditory pathway as expected. Therefore, unilateral CI users have an abnormal pattern of sensory stimulation. In this sense, the patient is advised and encouraged as to the fitting of hearing aids (HA) in no-implanted ear, especially in the presence of residual acoustic hearing in order to provide the benefits of binaural hearing. This condition is referred to bimodal hearing, when combining electric stimulation from the CI with acoustic stimulation from the contralateral ear provides to HA. Not enough data in the literature has focused on the child population to clarify or demonstrate the development of the auditory cortex in the bimodal hearing. Objective: To characterize the CAEP complex P1-N1-P2 users of bimodal stimulation and check for correlation with performance on tests of speech perception. Methods: A cross-sectional observational study, with the completion of the CAEP in six children using the Bimodal stimulation, the CAEP recording will be based in the methodology proposed by VENTURA (2008) using the system Smart EP USB Jr Intelligent Hearing Systems. The speech sound / of /, presented in free field, will be used. The potential will be recorded in three situations: monaural hearing (only CI); Bimodal hearing (IC and HA) and monoaural hearing (only HA). The examination will be held in three situations: monaural hearing (only IC); Bimodal hearing (IC and hearing aids) and hearing monaural (only the hearing aid). Data analysis of the cortical potential was performed after the marking of the presence or absence of the components of the N1-P1-P2 complex by two judges experienced in evoked potentials. It was verified that the record of the ECCP is a viable procedure for the assessment of children with bimodal stimulation and can assist in bilateral IC nomination process or the maintenance of bimodal stimulation.

<p>According to the World Health Organization, disabling hearing loss affects nearly 466 million people worldwide. Sensorineural hearing loss (SNHL), which is characterized as damage to the inner ear (e.g., cochlear hair cells) and/or to the neural pathways connecting the inner ear and brain, accounts for 90\% of all disabling hearing loss. One important clinical measure of SNHL is an auditory evoked potential called the auditory brainstem response (ABR). The ABR is a non-invasive measure of synchronous neural activity across the peripheral auditory pathway (auditory nerve to the midbrain), comprised of a series of multiple waves occurring within the first 10 milliseconds after stimulus onset. In humans, oftentimes ABRs are recorded using a high-density EEG electrode cap (e.g., with 32 channels). In our lab, a long-term goal is to establish and characterize reliable and efficient non-invasive measures of hearing loss in our pre-clinical chinchilla models of SNHL that can be directly related to human clinical measures. Thus, bridging the gap between chinchilla and human data collection by using analogous measures is imperative. \par</p><p><br></p><p>For this project, a 32-channel EEG electrode mini-cap for recording ABRs in chinchillas was studied. Firstly, the feasibility of this new method to record ABRs demonstrated. Secondly, the sources of bias and variability relevant to the mini cap were investigated. In this investigation, the ability of the mini cap to produce highly reliable, repeatable, reproducible, and valid ABRs was verified. Finally, the benefits of this new method, in comparison to our current approach using three subdermal electrodes, were characterized. It was found that ABR responses were comparable across channels both in magnitude and morphology when referenced to a tiptrode in the ipsilateral ear canal. Consequently, averaging across several channels led to a reduction in overall noise and the need for fewer repetitions (in comparison to the subdermal method) to obtain reliable response. Other methodological benefits of the mini cap included closer alignment with human ABR data collection, more efficient data collection, and capability for more in-depth data analyses, like source localization (e.g., in cortical responses). Future work will include collecting ABRs using the EEG mini-cap before and after noise exposure, as well as exploring the potential to leverage different channels to isolate brainstem and midbrain contributions to evoked responses from simultaneous recordings. </p>

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Study of the mammalian auditory system suggests that processes once thought exclusive to cortical structures also operate subcortically. Recently, this observation has extended to the detection of acoustic change. This thesis uses methods designed for the concurrent capture of auditory-evoked potential (AEP) components attributed to different subcortical and cortical sources. Using such an approach, Chapter 2 shows that 2-month-old infants respond to infrequent changes in sound source location with neural activity implicating both subcortically- and cortically-driven mechanisms of change-detection. Chapter 3 describes the development of a new stimulation protocol and presents normative data from adult listeners showing that the morphologies of several well-known subcortical and cortical AEP components are related. Finally, Chapter 4 uses the new methods developed in Chapter 3 to demonstrate that stimulus regularity not only affects neural activity at both subcortical and cortical structures, but that the activity localized to these structures is linked. Together, the studies presented in this thesis emphasize the potential for existing technologies to study the interaction of subcortical and cortical processing in human listeners. Moreover, the results of Chapters 2 through 4 lend support to models wherein change-detection is considered a distributed, and perhaps fundamental, attribute of the auditory hierarchy. / Thesis / Doctor of Philosophy (PhD)

INTRODUÇÃO: Os Potenciais Evocados Auditivos avaliam a atividade neuroelétrica da via auditiva desde o nervo auditivo até o córtex cerebral. A vectoeletronistagmografia permite analisar os canais semicirculares e/ou nervo vestibular inferior, verificando se existe comprometimento vestibular periférico ou central. A reabilitação vestibular é composta de exercícios físicos ativos e repetitivos de olhos, cabeça e corpo e/ou manobras específicas que visam diminuir a tontura e a instabilidade corporal, aumentar a estabilização no olhar, o controle postural e melhorar o bem-estar na realização das atividades do diaa- dia. Levando-se em conta a escassez de trabalhos na literatura que investiguem a via auditiva central em indivíduos com síndrome vestibular periférica e que sejam submetidos à reabilitação vestibular, torna-se importante conhecer o funcionamento do sistema auditivo central, desde o tronco encefálico até o córtex auditivo, em indivíduos com vestibulopatias periféricas. OBJETIVOS: caracterizar os potenciais evocados auditivos de curta, média e longa latências em indivíduos com vestibulopatias periféricas, bem como verificar a evolução destes potenciais e dos resultados obtidos no Dizziness Handicap Inventory (DHI) frente à reabilitação vestibular. MÉTODOS: Foram submetidos à avaliação eletrofisiológica da audição por meio dos potenciais evocados auditivos de tronco encefálico (PEATE), potencial evocado auditivo de média latência (PEAML) e potencial cognitivo (P300), bem como à aplicação do questionário DHI, antes e após reabilitação vestibular, 20 indivíduos com diagnóstico de Síndrome Vestibular Periférica Irritativa (SVPI) e 17 indivíduos com diagnóstico de Síndrome Vestibular Periférica Deficitária (SVPD), com idades entre 20 e 70 anos. RESULTADOS: Os resultados demonstraram que o grupo com SVPD apresentou maior porcentagem de resultados alterados no PEATE e PEAML. No que diz respeito aos tipos de alterações, pode-se observar no grupo com SVPD, alteração em tronco encefálico baixo no PEATE pré e pós RV; aumento das latências das ondas Na e Pa no PEAML pós RV, aumento da latência da onda Pa pré RV e efeito eletrodo para a amplitude Na- Pa pós RV. No grupo com SVPI, foi observada alteração do tipo outros no PEATE pré RV; aumento da latência da onda Pa no PEAML pré e pós RV e ambas as alterações para a amplitude Na-Pa pós RV. No estudo da evolução dos resultados pré e pós RV, pode-se observar maior porcentagem de resultados semelhantes para os três potenciais, em ambos os grupos avaliados. Na comparação do DHI pré e pós RV, ocorreram melhores resultados para os aspectos físico, emocional e funcional no grupo com SVPI e para os aspectos físico e emocional no grupo com SVPD. Tornam-se necessários mais estudos que avaliem a via auditiva central destes indivíduos para uma melhor caracterização dos achados eletrofisiológicos / INTRODUCTION: The auditory evoked potentials assess the neuroelectrical activity of the auditory pathway from the auditory nerve to the cerebral cortex. The vectoelectronystagmography analyzes the semicircular canals and/or inferior vestibular nerve, checking peripheral or central vestibular involvement. The vestibular rehabilitation therapy consists in active exercises and repetitive eyes exercises, head and body and/or specific maneuvers to reduce the dizziness and body instability, increase gaze stability and postural control and also improve well-being in daily activities. Taking into account the scarcity of studies in the literature that investigate the central auditory pathways in subjects who underwent vestibular rehabilitation therapy, it becames important to know the central auditory system from the brainstem to the auditory cortex, in subjects with peripheral vestibular disorders. OBJECTIVE: To characterize the auditory evoked potentials of short, middle and long latencies in subjects with peripheral vestibular disorders, as well as to evaluate the development of these potentials and the results obtained in the Dizziness Handicap Inventory (DHI) after vestibular rehabilitation therapy (VRT). METHODS: brainstem auditory evoked potential (BAEP), Auditory Middle- Latency Response (AMLR), cognitive potential (P300) and DHI were carried out in 20 subjects with Peripheral Vestibular Hyperfunction Syndrome and 17 subjects with Peripheral Vestibular Hypofunction Syndrome, aged between 20 and 70, before and after vestibular rehabilitation therapy. RESULTS: The results showed that the Peripheral Vestibular Hypofunction Syndrome group, presented higher percentage of altered results on BAEP and AMLR. Comparing the normal and altered results (qualitative analysis) between the groups in the BAEP, lower brainstem was predominantly observed in the Peripheral Vestibular Hypofunction Syndrome group before and after VRT; increased latencies of Na and Pa waves in AMLR after VRT, incresead latency of Pa wave in AMLR before VRT and electrode effect to the Na-Pa amplitude after VRT. The alteration predominantly observed in the Peripheral Vestibular Hyperfunction Syndrome group, was the other type one before VRT; increased latency of Pa wave in AMLR before and after VRT and both changes to the Na-Pa amplitude after VRT. In the study of the evolution before and after VRT, it was observed a higher percentage of similar results for the three potentials in both groups. Comparing results before and after VRT, the DHI greatest improvement occurred for the physical, emotional and functional aspects in the Peripheral Vestibular Hyperfunction Syndrome group and for the physical and emotional aspects in the Peripheral Vestibular Hypofunction Syndrome group. Further studies that evaluate the central auditory pathway of individuals with peripheral vestibular syndrome are needed to better characterize the electrophysiological findings

A Cetamina, antagonista não competitivo de receptores de glutamato do tipo NMDA, é uma substância com propriedades dissociativas originalmente utilizada como anestésico que apresenta a característica de intensificar as experiências sensoriais. Apesar de seus conhecidos efeitos sobre os aspectos cognitivos e comportamentais, poucos estudos préclínicos foram conduzidos para tentar detectar os efeitos físicos e/ou comportamentais da abstinência de Cetamina após consumo prolongado. Partindo do princípio de que os efeitos da Cetamina sobre a neurotransmissão glutamatérgica induzem alguns dos sintomas observados durante surtos esquizofrênicos, como as alucinações auditivas, e sabendo que o colículo inferior tem sua função ligada ao processamento da informação sensorial a estímulos sonoros, neste estudo avaliamos os efeitos da modulação glutamatérgica na área cortical pré-límbica (PrL) sobre os potenciais evocados auditivos eliciados (PEAs) no colículo inferior. As medidas foram realizadas no fim do tratamento, ou seja, no 14° dia, 24 horas e 6 dias após a retirada da cetamina. Em nossos resultados obtivemos que a administração local de NMDA, foi capaz de diminuir a amplitude dos PEAs, os quais foram recuperados 24 horas após. A cetamina sistêmica não foi capaz de diminuir os PEAs, uma provável consequência da interação com outros receptores além do NMDA. Os testes realizados 6 dias após a interrupção ao tratamento crônico de cetamina, demonstraram uma forma inesperada de U, diferente da curva padrão de U invertido. Além disso, encontramos que as alterações provocadas pela cetamina são dependentes dos níveis dos mecanismos dopaminérgico e glutamatérgicos. Estes resultados demonstram que o processamento auditivo no colículo inferior está sob controle direto no Pré límbico e permitem ampliar o conhecimento atual da neurobiologia por evidenciar novas informações do efeito crônico da cetamina. / Ketamine is a non-competitive NMDA receptor antagonist. It is a substance with dissociative properties originally used as anesthetic, which can intensify sensory experiences, being also capable of accentuating the psychotic state in patients with schizophrenia. Despite its known effect on cognitive aspects and behavior, there are few preclinical studies conducted to identify physical and behavioral effects of ketamine withdrawal after its long-term use. Moreover, little is known about the impact of repetitive use of ketamine on brain structures and their functioning. The inferior colliculus, part of the midbrain tectum, is mainly related to auditory information processing, sending information to the motor centers and participating in the modulation and expression of specific behaviors, such as attack and predatory. Therefore, it is related to the biological importance of sounds to survival. The auditory hallucinations induced by schizophrenic psychotic crisis has as neural correspondent the activation of inferior colliculus and cortical areas. It is not yet known which cortical area is connected to the modulation of alterations induced by electrophysiological potential registered in inferior colliculus. Considering that the effects of ketamine on glutamate neurotransmission induces the symptoms observed during schizophrenic psychotic crisis, such as auditory hallucinations, and that inferior colliculus is related to the sensory information processing and auditory pathways, the present work evaluates the effects of glutamate modulation on pre-limbic cortical area on auditory evoked potential startle in inferior colliculus of rats tested during and after interruption of chronic treatment with ketamine

Made available in DSpace on 2016-04-27T18:11:55Z (GMT). No. of bitstreams: 1 Natalia Ramos.pdf: 905403 bytes, checksum: fa987916f5277c93b467899da349596c (MD5) Previous issue date: 2012-02-14 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / ABR) contributes to the early diagnosis of hearing loss, once it allows a precise assessment of small children in different frequencies. Aim: To analyze air and bone-conduction tone-ABR, in order to estimate hearing thresholds of children from birth to three years of age with normal hearing and with sensorineural or mixed hearing losses. Method: Sample was divided in two groups: group I (GI) with normal hearing newborns submitted to air and bone-conduction tone-ABR at 500, 1000, 2000 and 4000 Hz; the latency and the presence of wave V were analyzed up to 20 dBnHL; group II (GII) comprised children with hearing loss submitted to the same of tone-ABR testing as GI, and also to air and bone-conduction behavioral audiometry. Both procedures were correlated in this group. Results: An increase of wave V latency was observed in GI as the intensity decreased, as well as higher latencies in lower frequencies either for air or bone stimuli. Concerning the air-conduction testing at 500 Hz, wave V was present up to 30 dBnHL, and at 1000 Hz, 91,66% of subjects presented it at 20 dBnHL; all subjects presented responses at 20 dBnHL for the other frequencies. Concerning bone-conduction testing, all subjects presented wave V at 20 dBnHL for all frequencies. GII results showed strong correlation for all frequencies tested air-conduction; however, the bone-conduction testing showed a strong correlation at 500, 1000 and 2000 Hz, and moderate correlation at 4000 Hz. Conclusion: The air and bone-conduction tone-ABR at 500, 1000, 2000 and 4000 Hz is useful in the audiological diagnosis of children in this age group, and there is a good correlation between its results and the behavioral audiometry The latency of wave V behaves inversely proportional to intensity; airconduction responses at 30 dBnHL for 500 Hz, and air and bone-conduction responses at 20 dBnHL for other frequencies may be considered within normal limits / Introdução: O Potencial Evocado Auditivo de Tronco Encefálico com estímulos de Frequência Específica (PEATE FE) auxilia no diagnóstico precoce da perda auditiva, uma vez que permite uma avaliação precisa da audição de crianças pequenas em diferentes frequências. Objetivo: Analisar os PEATE-FE por via aérea (VA) e via óssea (VO) para estimar os limiares auditivos de crianças, do nascimento aos três anos de idade, com audição normal e com perda auditiva sensorioneural ou mista. Método: A casuística foi dividida em dois grupos: grupo I (GI), composto por recém-nascidos com audição normal, sendo realizados os PEATE-FE nas frequências de 500, 1000, 2000 e 4000 Hz, tanto por VA quanto por VO, e analisados o tempo de latência e a presença da onda V até a intensidade de 20 dBnNA; grupo II (GII), composto por crianças com perda auditiva, sendo realizados os PEATE-FE nas mesmas frequências do GI e a audiometria comportamental, também por VA e por VO. Neste grupo, foram correlacionados os dois procedimentos. Resultados: No GI, pôde-se observar aumento da latência da onda V com a diminuição da intensidade, como também maiores latências nas frequências mais baixas, tanto na VA quanto na VO. Com relação à VA, na frequência de 500 Hz, houve presença da onda V até 30 dBnNA, e em 1000 Hz, 91,66 % dos sujeitos a obtiveram em 20 dBnNA; nas demais frequências, todos apresentaram resposta em 20 dBnNA. Na VO, todos obtiveram presença da onda V em 20 dBnNA em todas as frequências estudadas. Os resultados do GII mostraram forte correlação nas quatro frequências estudadas por VA; já na VO, foi encontrada forte correlação nas frequências de 500, 1000 e 2000 Hz e moderada em 4000 Hz. Conclusão: O PEATE-FE por VA e por VO auxiliam no diagnóstico audiológico de crianças da faixa etária estudada nas frequências de 500, 1000, 2000 e 4000 Hz, havendo boa correlação entre seus resultados e o da audiometria comportamental. A latência da onda V se comporta de maneira inversamente proporcional à intensidade, sendo que pode ser considerado como padrão de normalidade em: 30 dBnNA para 500 Hz por VA e 20 dBnNA para as demais frequências na VA e VO

Odontocetes use echolocation to detect, track, and discriminate their prey, as well as negotiate their environment. Their hearing abilities match the frequency of greatest sensitivity to the higher frequencies used for foraging and navigation. Hearing and echolocation together provide odontocetes with a highly developed biosonar system. This dissertation examines the hearing ability of several odontocete species to understand what signals they can perceive during echolocation. The variability in hearing ranges between species is examined in the context of phylogenetic and ecological differences among taxa. An autonomous hydrophone array is also developed that could be used in an expanded form in field deployments to study echolocation signals in a wider range of species. Methods for measuring hearing sensitivity include both psychophysical and electrophysiological procedures. Behavioral methods require a large time commitment, for both training and data collection, and can only be performed on captive dolphins. Auditory evoked potential (AEP) methods are non-invasive, rapid measurements of the brain's response to sound stimuli and allow for audiograms to be collected on stranded, high risk dolphins. By determining the hearing abilities of odontocetes either in captivity or during stranding, data can be collected about inter- and intraspecies variability, and the occurrence of hearing impairment. It can also be used as another diagnostic tool to determine the releasability of a stranded animal. A juvenile male short-finned pilot whale (Globicephala macrorhynchus) that stranded in Curacao had severe hearing impairment at all frequencies tested. Four female short-finned pilot whales tested had the best sensitivity at 40 kHz. The juveniles had greater high frequency sensitivity than the adult pilot whales. Cutoff frequencies were between 80 and 120 kHz. Hearing sensitivity was determined for the two mother/calf pairs of Risso's dolphins (Grampus griseus) before and after antibiotic treatment in order to measure any potential effects of antibiotic treatment. Greatest sensitivity occurred at 40 kHz and cutoff frequencies were around 120 kHz for all dolphins tested. Changes in hearing sensitivity after antibiotic dosage were 12 dB or less in all cases except one. The adult female Betty showed a threshold shift at 120 kHz of 54 dB from May to June, which partially demonstrates the presence of an ototoxic effect at one frequency. Dosages of antibiotics during drug treatment detailed in this study should be considered safe dosages of antibiotics for Risso's dolphins. AEP and behavioral methods were used to collect audiograms for three Stenella spp. dolphins. The frequency of best hearing for the Atlantic spotted dolphin and the spinner dolphin was 40 kHz, and their upper cutoff frequencies were above 120 kHz. The pantropical spotted dolphin had the greatest sensitivity at 10 kHz, and had severe high frequency hearing loss with a cutoff frequency between 14 and 20 kHz. Comparisons of high frequency hearing sensitivities among the species tested show two distinct groups. Short-finned pilot whales and Risso's dolphins have a cutoff frequency below 120 kHz, whereas Stenella spp. dolphins have cutoff frequencies above 120 kHz. Expanding the comparison to include other species, killer whales, pygmy killer whales, false killer whales, and long-finned pilot whales also have cutoff frequencies below 120 kHz. Common bottlenose dolphins, white-beaked dolphins, Indo-Pacific humpback dolphins, rough-toothed dolphins, and common dolphins have cutoff frequencies above 120 kHz. Genetic evidence exists for two subfamilies within Delphinidae (Vilstrup et al., 2011) and those species with cutoff frequencies below 120 kHz belong to the subfamily Globicephalinae and those species with cutoff frequencies above 120 kHz belong to the subfamily Delphininae. An autonomous, field-deployable hydrophone array was developed to measure free-swimming echolocation. The array contained 25 hydrophones, two cameras, and a synchronization unit on a PVC frame. The distinct click train was used to time-align all 25 channels, and the light was used to synchronize the video and acoustic recordings. Echolocation beam patterns were calculated and preliminary evidence shows a free-swimming dolphin utilizes head movement, beam steering and beam focusing. Among all areas of cetacean biology more research is necessary to gain a clearer picture of how odontocetes have adapted to function in their acoustic environment. The array system developed can be used to study how dolphins use echolocation in the wild, the impacts of anthropogenic sound on echolocation production, and the potential consequences of high frequency hearing loss.