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No description available.

<p>The superior olivary complex (SOC) is comprised of nuclei involved in sound localization. To compute interaural sound level differences, lateral superior olive (LSO) neurons integrate converging glutamatergic inputs from the cochlear nucleus with glycinergic inputs from the medial nucleus of the trapezoid body (MNTB). To compute interaural timing differences, the medial superior olive (MSO) integrates converging glutamatergic inputs from the ipsilateral and contralateral cochlear nucleus. The MSO also receives a major inhibitory input from the MNTB. N-methyl-D-aspartate receptors (NMDARs) are thought to play a role in the developmental refinement of these auditory brainstem pathways. The GluN2A and GluN2B NMDAR subunits confer widely different properties on NMDARs, substantially affecting plasticity. We assessed postnatal developmental messenger RNA (mRNA) expression of GluN1, GluN2A and GluN2B subunits in the LSO, MSO and MNTB using quantitative <em>in-situ</em> hybridization in tissue from 10 litters, ages postnatal day 1 to 36 (P1-36).</p> <p>GluN1 mRNA expression in the LSO, MSO and MNTB decreased with age. In all three nuclei, GluN2B mRNA expression was highest during the first postnatal week, dropping to low levels thereafter. In the LSO, GluN2A levels increased, then decreased to moderate levels. In the MNTB, GluN2A levels decreased from initially high levels. In the MSO, GluN2A levels increased to intermediate levels. The GluN2A/2B ratio increased 2-fold between P1 and P8 in the MNTB, whereas the ratio increased 3-fold between P8 and P15 in the LSO and MSO. The changes in GluN2A:GluN2B ratio are consistent with a developmental switch from GluN2B-containing NMDARs to GluN2A-containing NMDARs. These results are consistent with prior electrophysiological experiments that show NMDAR-mediated currents declining with age in the aVCN-MNTB, aVCN-LSO and MNTB-LSO pathways. The GluN2A subunit exhibited different developmental expression patterns in MNTB, LSO and MNTB, which suggests that GluN2A mRNA expression is locally regulated between nuclei, whereas GluN2B may be globally regulated.</p> / Master of Science (MSc)

<p>The lateral superior olive (LSO) is a binaural nucleus that is critical for azimuthal sound localization. Bipolar principal cells of the LSO compute interaural level differences (ILDs) by comparing converging excitatory and inhibitory inputs driven by either ear. More specifically, this computation relies on integrating excitatory inputs from the ipsilateral cochlear nucleus with inhibitory, GABA/glycinergic inputs from the medial nucleus of the trapezoid body (MNTB), which are driven by sound originating at the contralateral ear. In order to reliably compute ILDs, the converging inputs must represent sounds of the same frequency. This specificity emerges during the first few weeks of postnatal life in rats as a result of functional and anatomical refinement. Interestingly, significant refinement of this auditory circuit occurs in the absence auditory experience. We focused on changes in the subcellular location of MNTB inputs and the expression of vesicular proteins before hearing onset.</p> <p>The subcellular distribution of inputs onto a neuron heavily influences synaptic integration and the mature distribution likely emerges during a period of circuit refinement. Little is known about how the inputs are distributed onto LSO principal cells and how the mature distribution is achieved. We studied the distribution of inhibitory inputs onto LSO neurons and found that significant re- distribution occurs before hearing onset. The mechanisms underlying the refinement of the inhibitory MNTB projection are not well understood but could be related to the transient co-transmission of the excitatory neurotransmitter glutamate. We studied the expression of vesicular proteins that may regulate the release of GABA/glycine and glutamate at the immature MNTB terminal. We found that MNTB terminals transiently express two Ca++ sensors, which may be associated with the different release properties for GABA/glycine and glutamate. Lastly, we asked one specific example of what controls the expression and sorting of vesicular proteins at the immature MNTB terminal.</p> / Doctor of Philosophy (PhD)

Cette thèse porte sur la perception visuelle, auditive et audiovisuelle des voyelles nasales [ɑ̃] (« lent »),[ɔ̃] (« long ») et [ɛ̃] (« lin ») par des adultes devenus sourds, implantés cochléaires et implantés dutronc cérébral. L’étude sur la perception visuelle des voyelles, auprès de 22 adultes devenus sourds,redéfinit les sosies labiaux des voyelles nasales et propose une mise à jour de la classification desvisèmes. Trois études sur l’identification auditive des voyelles nasales auprès de 82, 15 et 10 adultesimplantés cochléaires mettent en évidence leur difficulté à reconnaitre les trois voyelles nasales, qu’ilsperçoivent comme des voyelles orales. Les analyses acoustiques et perceptives suggèrent que lesadultes implantés cochléaires s’appuient sur les informations fréquentielles des deux premiers picsspectraux mais négligent les informations d’intensité relative de ces pics. D’après l’étude menéeauprès de 13 adultes implantés du tronc cérébral, des informations acoustiques linguistiques sonttransmises par l’implant du tronc cérébral mais la fusion entre les informations auditives et visuellespourrait être optimisée pour l’identification des voyelles. Enfin, une enquête auprès de 179orthophonistes pointe le besoin d’une information sur la définition phonétique articulatoire actualiséedes voyelles [ɑ̃] et [ɛ̃]. / This thesis focuses on the visual, auditory and auditory-visual perception of french nasal vowels [ɑ̃](« lent »), [ɔ̃] (« long ») and [ɛ̃] (« lin ») by Cochlear Implant (CI) and Auditory Brainstem Implant(ABI) adults users. The study on visual perception of vowels, with 22 deafened adults, redefines thelip configuration of french nasal vowels and provides an update of the classification of vocalic visualphonemes. Three studies on auditory identification of nasal vowels with 82, 15 and 10 CI usershighlight their difficulty in recognizing the three nasal vowels, which they perceive as oral vowels.Acoustic and perceptual analyzes suggest that adults with CI rely on frequency informations of thefirst two spectral peaks but miss the informations of relative intensity of these peaks. The study with13 ABI users show that some linguistic acoustic cues are transmitted by the ABI but the fusion ofauditory and visual features could be optimized for the identification of vowels. Finally, a survey of179 Speech Language and Hearing Therapists show the need of an update on the phonetic articulationof french nasal vowels [ɑ̃] and [ɛ̃].

Cette thèse porte sur la perception visuelle, auditive et audiovisuelle des voyelles nasales [ɑ̃] (« lent »),[ɔ̃] (« long ») et [ɛ̃] (« lin ») par des adultes devenus sourds, implantés cochléaires et implantés dutronc cérébral. L’étude sur la perception visuelle des voyelles, auprès de 22 adultes devenus sourds,redéfinit les sosies labiaux des voyelles nasales et propose une mise à jour de la classification desvisèmes. Trois études sur l’identification auditive des voyelles nasales auprès de 82, 15 et 10 adultesimplantés cochléaires mettent en évidence leur difficulté à reconnaitre les trois voyelles nasales, qu’ilsperçoivent comme des voyelles orales. Les analyses acoustiques et perceptives suggèrent que lesadultes implantés cochléaires s’appuient sur les informations fréquentielles des deux premiers picsspectraux mais négligent les informations d’intensité relative de ces pics. D’après l’étude menéeauprès de 13 adultes implantés du tronc cérébral, des informations acoustiques linguistiques sonttransmises par l’implant du tronc cérébral mais la fusion entre les informations auditives et visuellespourrait être optimisée pour l’identification des voyelles. Enfin, une enquête auprès de 179orthophonistes pointe le besoin d’une information sur la définition phonétique articulatoire actualiséedes voyelles [ɑ̃] et [ɛ̃]. / This thesis focuses on the visual, auditory and auditory-visual perception of french nasal vowels [ɑ̃](« lent »), [ɔ̃] (« long ») and [ɛ̃] (« lin ») by Cochlear Implant (CI) and Auditory Brainstem Implant(ABI) adults users. The study on visual perception of vowels, with 22 deafened adults, redefines thelip configuration of french nasal vowels and provides an update of the classification of vocalic visualphonemes. Three studies on auditory identification of nasal vowels with 82, 15 and 10 CI usershighlight their difficulty in recognizing the three nasal vowels, which they perceive as oral vowels.Acoustic and perceptual analyzes suggest that adults with CI rely on frequency informations of thefirst two spectral peaks but miss the informations of relative intensity of these peaks. The study with13 ABI users show that some linguistic acoustic cues are transmitted by the ABI but the fusion ofauditory and visual features could be optimized for the identification of vowels. Finally, a survey of179 Speech Language and Hearing Therapists show the need of an update on the phonetic articulationof french nasal vowels [ɑ̃] and [ɛ̃].

Os potenciais evocados auditivos de tronco encefálico (PEATE) são um instrumento clínico muito útil na avaliação da maturação das vias auditivas em crianças nascidas pré-termo. Objetivos: Observar a maturação da via auditiva pela análise PEATE em crianças nascidas prétermo em três idades (4, 12 e 20 meses de idade). Casuística e Método: Coorte, individual, observacional, comparativo e contemporâneo. O fator em estudo foi crianças nascidas pré-termo e o desfecho à observação da maturação da via auditiva neste grupo, pela análise PEATE, em três avaliações (aos 4, 12 e 20 meses de idade), precedido de avaliação otorrinolaringológica e audiológica com objetivo de garantir que não apresentavam alteração auditiva. Resultados: Ingressaram 73 crianças pré-termo. Não foi encontrada diferença estatística (P>0,05) na comparação dos resultados entre os gêneros, bem como interaural. Houve diferença estatiticamente significante entre idade gestacional, as latências absolutas e intervalos interpicos nas três avaliações realizadas, ocorrendo uma diminuição das latências com o aumento da idade. Verificamos que a maturação da onda I foi mais rápida, e a maturação da onda V foi mais lenta. Podemos perceber que a maturação da via auditiva até o tronco encefálico segue o sentido caudorostral, sendo a da via periférica mais precoce, e a da rostral, mais tardia. Conclusão: Com base nos achados deste estudo, recomendamos que a aplicação do procedimento de avaliação audiológica através do PEATE em crianças nascidas pré-termo, pelo menos até os 20 meses de idade, seja realizado levando-se em conta a idade gestacional a fim de se obter análises fidedignas. / Brainstem Auditory Evoked Potential (BAEP) is a very useful clinical instrument in the evaluation of the auditory pathways maturation in preterm children. Objective: To observe the maturation of the auditory pathway with the use of the BAEP analysis in preterm children at three different ages (four, 12 and 20 months). Casuistry and Method: Group, individual, observational, comparative and contemporary. Preterm children and the outcome to observation of the auditory pathway maturation by the BAEP analysis in three evaluations (at 4, 12 and 20 months of age) were studied. The procedures were preceded by otolaryngological and auditory evaluation with the objective to guarantee the non presence of auditory alteration. Results: Seventy-three preterm children participated in the study. Statistically significant difference was not found (P> 0,05) in the comparison between genders and between ears. There was a statistically significant difference among gestational ages, absolute latencies and interpic intervals in the three evaluations conducted, occurring a reduction of latencies with age increase. We verified that maturation of wave I was faster and the maturation of wave V was slower. We could perceive that the maturation of the auditory pathway up to the brainstem follows the caudorostral direction, being the peripheral pathway more precocious and the rostral pathway more delayed. Conclusion: Based on the findings of this study, we recommend the application of the audiological evaluation procedure using BAEP in preterm children, at least until 20 months of age, by taking into account the gestational age in order to obtain reliable analyses.

Os potenciais evocados auditivos de tronco encefálico (PEATE) são um instrumento clínico muito útil na avaliação da maturação das vias auditivas em crianças nascidas pré-termo. Objetivos: Observar a maturação da via auditiva pela análise PEATE em crianças nascidas prétermo em três idades (4, 12 e 20 meses de idade). Casuística e Método: Coorte, individual, observacional, comparativo e contemporâneo. O fator em estudo foi crianças nascidas pré-termo e o desfecho à observação da maturação da via auditiva neste grupo, pela análise PEATE, em três avaliações (aos 4, 12 e 20 meses de idade), precedido de avaliação otorrinolaringológica e audiológica com objetivo de garantir que não apresentavam alteração auditiva. Resultados: Ingressaram 73 crianças pré-termo. Não foi encontrada diferença estatística (P>0,05) na comparação dos resultados entre os gêneros, bem como interaural. Houve diferença estatiticamente significante entre idade gestacional, as latências absolutas e intervalos interpicos nas três avaliações realizadas, ocorrendo uma diminuição das latências com o aumento da idade. Verificamos que a maturação da onda I foi mais rápida, e a maturação da onda V foi mais lenta. Podemos perceber que a maturação da via auditiva até o tronco encefálico segue o sentido caudorostral, sendo a da via periférica mais precoce, e a da rostral, mais tardia. Conclusão: Com base nos achados deste estudo, recomendamos que a aplicação do procedimento de avaliação audiológica através do PEATE em crianças nascidas pré-termo, pelo menos até os 20 meses de idade, seja realizado levando-se em conta a idade gestacional a fim de se obter análises fidedignas. / Brainstem Auditory Evoked Potential (BAEP) is a very useful clinical instrument in the evaluation of the auditory pathways maturation in preterm children. Objective: To observe the maturation of the auditory pathway with the use of the BAEP analysis in preterm children at three different ages (four, 12 and 20 months). Casuistry and Method: Group, individual, observational, comparative and contemporary. Preterm children and the outcome to observation of the auditory pathway maturation by the BAEP analysis in three evaluations (at 4, 12 and 20 months of age) were studied. The procedures were preceded by otolaryngological and auditory evaluation with the objective to guarantee the non presence of auditory alteration. Results: Seventy-three preterm children participated in the study. Statistically significant difference was not found (P> 0,05) in the comparison between genders and between ears. There was a statistically significant difference among gestational ages, absolute latencies and interpic intervals in the three evaluations conducted, occurring a reduction of latencies with age increase. We verified that maturation of wave I was faster and the maturation of wave V was slower. We could perceive that the maturation of the auditory pathway up to the brainstem follows the caudorostral direction, being the peripheral pathway more precocious and the rostral pathway more delayed. Conclusion: Based on the findings of this study, we recommend the application of the audiological evaluation procedure using BAEP in preterm children, at least until 20 months of age, by taking into account the gestational age in order to obtain reliable analyses.