Introdução: A desnutrição energético-protéica é um dos maiores problemas de saúde pública no Brasil, ocorrendo mais frequentemente em pré-escolares e determinando o comprometimento do crescimento. A desnutrição pode provocar alterações no sistema nervoso central, dependendo da intensidade, da época de incidência e da duração da doença, comprometendo irreversivelmente as funções intelectuais. Levando-se em consideração a importância da integridade do Sistema Auditivo Periférico e Central na aquisição e desenvolvimento de fala, linguagem e aprendizado, torna-se imprescindível que anormalidades auditivas tanto periféricas como centrais sejam identificadas e tratadas precocemente nesta população. Objetivo: Caracterizar os achados das avaliações comportamentais, eletroacústicas e eletrofisiológicas da audição em crianças com desnutrição, bem como compará-los aos obtidos em crianças saudáveis da mesma faixa etária. Métodos: Foram realizados exames de audiometria tonal, logoaudiometria, teste dicótico de dígitos, imitanciometria, potencial evocado auditivo de tronco encefálico (PEATE) e potencial evocado auditivo de longa latência (PEALL) em 31 crianças desnutridas (grupo estudo) e 34 crianças saudáveis (grupo controle), com idade entre 7 e 12 anos, de ambos os gêneros. Resultados: Na análise dos dados quantitativos da audiometria tonal foi observada uma diferença estatisticamente significante entre os grupos para os limiares auditivos nas frequências de 250 e 8000 Hz, tendo o grupo estudo apresentado limiares auditivos mais elevados. Na análise qualitativa, não houve diferença estatisticamente significante entre os grupos, apesar de duas crianças do grupo estudo apresentarem perda auditiva discreta. Na análise dos dados qualitativos, não foram encontradas alterações na logoaudiometria para os dois grupos. No teste dicótico de dígitos, houve diferença estatisticamente significante entre os grupos, sendo observada uma maior proporção de crianças com alteração no grupo estudo. Ambos os grupos apresentaram resultados alterados na imitanciometria, não havendo diferença estatisticamente significante entre os grupos. Ambos os grupos apresentaram resultados normais do PEATE. Na análise dos dados quantitativos dos PEALL, verificou-se diferença estatisticamente significante entre os grupos para as latências dos componentes P1, N1 e P300, sendo que o grupo estudo apresentou latências maiores para todos os componentes. Na avaliação da amplitude do P300, houve diferença estatisticamente significante entre as orelhas direita e esquerda do grupo controle, sendo a amplitude do P300 maior na orelha direita. Por sua vez, no grupo estudo, não houve diferença significativa entre as orelhas direita e esquerda. Tanto o grupo controle quanto o grupo estudo apresentaram alterações nos resultados do PEALL, havendo diferença estatisticamente significante entre os grupos para os componentes P1, N1 e P300, sendo que o grupo estudo apresentou maior ocorrência de alterações. O tipo de alteração predominante nos componentes P1 e P300 foi o aumento de latência e, para o componente N1, foi a ausência de resposta no grupo estudo; para o grupo controle, o tipo de alteração predominante nos componentes P1, N1 e P300 foi o aumento de latência. Devido ao predomínio de crianças desnutridas de grau leve (58,1%), não foi possível estabelecer uma correlação entre o grau da desnutrição e a alteração dos PEALL. Conclusão: Crianças com desnutrição apresentaram mais alterações na avaliação comportamental da audição (audiometria tonal e teste dicótico de dígitos) e nos PEALL do que as crianças saudáveis, sugerindo déficit na via auditiva central e alteração no processamento da informação acústica. Há a necessidade de mais estudos para melhor caracterizar as alterações fonoaudiológicas e audiológicas desta população. / Introduction: Protein-energy malnutrition is a major public health problem in Brazil. It is more frequent among pre-school aged children and it compromises growth. Malnutrition may cause changes to the central nervous system depending on its intensity, time of incidence and duration, irreversibly compromising intellectual functions. Considering the importance of Peripheral and Central Auditory System integrity to the acquisition and development of speech, language and learning, it is crucial that both peripheral and central auditory abnormalities are identified and treated early in this population. Objective: To describe the findings of behavioral, electroacoustic and electrophysiological auditory assessments of malnourished children, as well as comparing them with findings from healthy children within the same age group. Methods: The following tests were performed in 31 malnourished children (study group) and 34 healthy children (control group), aged 7 to 12, from both genders: pure tone audiometry, speech audiometry, dichotic digit test, immittance measures, brainstem auditory evoked potential (BAEP) and long-latency auditory evoked potential (LLAEP). Results: While analyzing quantitative data from pure tone audiometry we observed statistically significant differences between groups for hearing thresholds at frequencies of 250 and 8000 Hz; the study group had higher hearing thresholds. As for quantitative analysis, there was no statistically significant difference between groups, although two children in the study group showed slight hearing loss. While analyzing qualitative data we did not find any changes in speech audiometry in any of the groups. As for the dichotic digit test, there was a statistically significant difference between groups, with a higher proportion of abnormal children in the study group. Both groups showed abnormal immittance measures results, although there was no statistically significant difference between the groups. Both showed normal BAEP results. When analyzing quantitative LLAEP data we observed a statistically significant difference between groups in terms of latency of components P1, N1 and P300; the study group had higher latencies for all components. When analyzing P300 amplitudes, there was a statistically significant difference between the right and left ears in the control group; P300 amplitudes was wider for the right ear. On the other hand, the study group did not show any statistically significant difference between the right and left ears. Both the control and study group shoed abnormal LLAEP results. There was a statistically significant difference between groups for components P1, N1 and P300; abnormalities were more frequent in the study group. The type of predominant abnormality in components P1 and P300 was increased latency and for component N1 it was lack of response in the study group; for the control group the type of predominant abnormality in components P1, N1 and P300 was increased latency. Because most children were only slightly malnourished (58.1%), it was not possible to establish a correlation between the level of malnutrition and LLAEP abnormalities. Conclusion: Malnourished children showed more abnormalities in auditory behavioral assessment (pure tone audiometry and dichotic digit test) and LLAEP than healthy children. This suggests a deficit in central auditory pathways and abnormalities in the processing of acoustic information. Further studies are necessary to better describe speech and language and hearing abnormalities in this population.

Dans ce travail, nous étudions les mécanismes du changement de langue lors de la reconnaissance visuelle de mots chez des trilingues français /anglais /espagnol. Dans un premier temps, nous avons examiné les processus d’accès pour chacune des langues étudiées, indépendamment de la présentation des autres langues. Nous nous sommes ensuite interrogés sur les relations entre les langues et l’organisation lexicale sous-jacente dans la mémoire multilingue, ainsi que la mise en place des mécanismes cognitifs permettant de passer d’une langue à une autre. Dans cette perspective, nous avons réalisé trois séries d’expériences afin d’examiner l’influence mutuelle des langues et le coût cognitif consécutif à un changement de langue lors de la reconnaissance visuelle de mots isolés. Nous avons comparé le traitement de mots spécifiques à différentes langues (ayant un degré de recouvrement orthographique minimal) en faisant varier les situations de changement et en recueillant des données comportementales et chronométriques dans des tâches de décision lexicale, de catégorisation sémantique et d’amorçage sémantique par traduction. Les résultats mettent en évidence un ralentissement global du traitement dû au changement pour les trois langues. Nous avons également observé un coût cognitif suite à un changement de langue pour les trois langues, mais plus important lorsqu’il s’opère entre les deux langues les moins maîtrisées (L2 vers L3 et L3 vers L2). Les données obtenues confirment l’hypothèse d’unités lexicales intégrées au sein d’un même lexique dans la mémoire multilingue. Les résultats sont interprétés dans leur ensemble dans le cadre des principaux modèles de la mémoire bilingue/multilingue. / The present work focuses on language switching mechanisms during visual word recognition in French / English / Spanish trilinguals. First, we examined access to processing for each language, independently from the presentation of other languages. Then, our concern was to determine the different relations between languages and the underlying lexical organization inside the multilingual memory, as well as the activation of cognitive mechanisms allowing language switching. With this goal in mind, we performed three series of experiments to examine the influences between the languages, and the cognitive cost subsequent to a language switching during visual word recognition. We compare the processing of non-cognate words belonging to the three languages, manipulating the language switching situations and recording behavioral and electrophysiological data during lexical decision, semantic categorization and semantic translation priming. Results of these experiments highlight a general slowdown of processing consecutive to a language switch for all languages. Moreover, we observed a cognitive cost related to language switching for all the three languages, but bilaterally larger when it concerns the two non-dominant languages (L2 to L3 and L3 to L2). The recording data confirms the hypothesis of lexical representations integrated into a shared lexicon of multilingual memory. The results are interpreted in the light of the main models accounting for bilingual memory.

Abstract Audio-oral speech and visuo-manual sign language as used by the Deaf community are two very different realizations of the human linguistic communication system. Sign language is not only used by the hearing impaired but also by different groups of hearing individuals. To date, there is a great discrepancy in scientific knowledge about signed and spoken languages. Particularly little is known about the integration of the two systems, even though the vast majority of deaf and hearing signers also have a command of some form of speech. This neurolinguistic study aimed to achieve basic knowledge about semantic integration mechanisms across speech and sign language in hearing native and non-native signers. Basic principles of sign processing as reflected in electrocortical brain activation and behavioral decisions were examined in three groups of study participants: Hearing native signers (children of deaf adults, CODAs), hearing late learned signers (professional sign language interpreters), and hearing non-signing controls. Event-related brain potentials (ERPs) and behavioral response frequencies were recorded while the participants performed a semantic decision task for priming lexeme pairs. The lexeme pairs were presented either within speech (spoken prime-spoken target) or across speech and sign language (spoken prime-signed target). Target-related ERP responses were subjected to temporal principal component analyses (tPCA). The neurocognitive basis of semantic integration processes were assessed by analyzing different ERP components (N170, N400, late positive complex) in response to the antonymic and unrelated targets. Behavioral decision sensitivity to the target lexemes is discussed in relation to the measured brain activity. Behaviorally, all three groups of study participants performed above chance level when making semantic decisions about the primed targets. Different result patterns, however, hinted at three different processing strategies. As the target-locked electrophysiological data was analyzed by PCA, for the first time in the context of sign language processing, objectively allocated ERP components of interest could be explored. A little surprisingly, the overall study results from the sign-naïve control group showed that they performed in a more content-guided way than expected. This suggested that even non-experts in the field of sign language were equipped with basic skills to process the cross-linguistically primed signs. Behavioral and electrophysiological study results together further brought up qualitative differences in processing between the native and late learned signers, which raised the question: can a unitary model of sign processing do justice to different groups of sign language users? / Tiivistelmä Kuuloaistiin ja ääntöelimistön motoriikkaan perustuva puhe ja kuurojen yhteisön käyttämä, näköaistiin ja käsien liikkeisiin perustuva viittomakieli ovat kaksi varsin erilaista ihmisen kielellisen viestintäjärjestelmän toteutumismuotoa. Viittomakieltä käyttävät kuulovammaisten ohella myös monet kuulevat ihmisryhmät. Tähänastinen tutkimustiedon määrä viittomakielistä ja puhutuista kielistä eroaa huomattavasti. Erityisen vähän on tiedetty näiden kahden järjestelmän yhdistämisestä, vaikka valtaosa kuuroista ja kuulevista viittomakielen käyttäjistä hallitsee myös puheen jossain muodossa. Tämän neurolingvistisen tutkimuksen tarkoituksena oli hankkia perustietoja puheen ja viittomakielen välisistä semanttisista yhdistämismekanismeista kuulevilla, viittomakieltä äidinkielenään tai muuna kielenä käyttävillä henkilöillä. Viittomien prosessoinnin perusperiaatteita, jotka ilmenevät aivojen sähköisen toiminnan muutoksina ja valintapäätöksinä, tutkittiin kolmessa koehenkilöryhmässä: kuulevilla viittomakieltä äidinkielenään käyttävillä henkilöillä (kuurojen aikuisten kuulevilla ns. CODA-lapsilla, engl. children of deaf adults), kuulevilla viittomakielen myöhemmin oppineilla henkilöillä (viittomakielen ammattitulkeilla) sekä kuulevilla viittomakieltä osaamattomilla verrokkihenkilöillä. Tapahtumasidonnaiset herätepotentiaalit (ERP:t) ja käyttäytymisvasteen frekvenssit rekisteröitiin koehenkilöiden tehdessä semanttisia valintoja viritetyistä (engl. primed) lekseemipareista. Lekseemiparit esitettiin joko puheena (puhuttu viritesana – puhuttu kohdesana) tai puheen ja viittomakielen välillä (puhuttu viritesana – viitottu kohdesana). Kohdesidonnaisille ERP-vasteille tehtiin temporaaliset pääkomponenttianalyysit (tPCA). Semanttisten yhdistämisprosessien neurokognitiivista perustaa arvioitiin analysoimalla erilaisia ERP-komponentteja (N170, N400, myöhäinen positiivinen kompleksi) vastineina antonyymisiin ja toisiinsa liittymättömiin kohteisiin. Käyttäytymispäätöksen herkkyyttä kohdelekseemeille tarkastellaan suhteessa mitattuun aivojen aktiviteettiin. Käyttäytymisen osalta kaikki kolme koehenkilöryhmää suoriutuivat satunnaistasoa paremmin tehdessään semanttisia valintoja viritetyistä kohdelekseemeistä. Erilaiset tulosmallit viittaavat kuitenkin kolmeen erilaiseen prosessointistrategiaan. Kun kohdelukittua elektrofysiologista dataa analysoitiin pääkomponenttianalyysin avulla ensimmäistä kertaa viittomakielen prosessoinnin yhteydessä, voitiin tutkia tarkkaavaisuuden objektiivisesti allokoituja ERP-komponentteja. Oli jossain määrin yllättävää, että viittomakielellisesti natiivin verrokkiryhmän tulokset osoittivat sen jäsenten toimivan odotettua sisältölähtöisemmin. Tämä viittaa siihen, että viittomakieleen perehtymättömilläkin henkilöillä on perustaidot lingvistisesti ristiin viritettyjen viittomien prosessointiin. Yhdessä käyttäytymisperäiset ja elektrofysiologiset tutkimustulokset toivat esiin laadullisia eroja prosessoinnissa viittomakieltä äidinkielenään puhuvien henkilöiden ja kielen myöhemmin oppineiden henkilöiden välillä. Tämä puolestaan johtaa kysymykseen, voiko yksi viittomien prosessointimalli soveltua erilaisille viittomakielen käyttäjäryhmille?

Introdução: Indivíduos com Transtorno do Espectro do Autismo (TEA) apresentam prejuízos nas interações sociais, comunicação e comportamento, além de poderem apresentar alterações cognitivas e de linguagem. Tendo em vista que o desenvolvimento da linguagem depende do funcionamento adequado da via auditiva periférica e central, ressalta-se a importância da avaliação audiológica completa, em especial, da avaliação do Sistema Nervoso Auditivo Central nessa população, tanto no diagnóstico como durante o processo terapêutico. Objetivos: caracterizar o Potencial Evocado Auditivo de Tronco Encefálico (PEATE) com estímulos clique e fala e o Potencial Evocado Auditivo de Longa Latência (PEALL) com estímulos tone burst e de fala, em indivíduos com TEA. Metodologia: participaram deste estudo 30 indivíduos na faixa etária de sete a 12 anos, de ambos os sexos, sendo 15 do grupo estudo (GE - crianças com diagnóstico de TEA) e 15 do grupo controle (GC - crianças com desenvolvimento típico - DT), pareados por sexo e idade. Foram realizados os seguintes procedimentos: anamnese, meatoscopia, avaliação audiológica básica (audiometria tonal, logoaudiometria e imitanciometria), e avaliação eletrofisiológica da audição (PEATE com estímulos clique e fala, e PEALL com estímulos tone burst e fala). Todos os exames foram realizados no Centro de Docência e Pesquisa do Departamento de Fisioterapia, Fonoaudiologia e Terapia Ocupacional da Faculdade de Medicina da Universidade de São Paulo. Resultados: No PEATE com estímulo clique, o valor médio de latência da onda I apresentou-se maior para orelha direita em ambos os grupos (valor-p = 0,037), ocorrendo assim o efeito orelha. Observou-se, também, que o interpico III - V no grupo com TEA foi maior do que o obtido no grupo com DT (valor-p = 0,046). No PEATE com estímulo de fala, a latência absoluta da onda V foi menor no grupo com TEA quando comparado ao grupo com DT (valor-p = 0,011). No PEALL, tanto para o estímulo tone burst quanto para o estímulo de fala, a latência do componente N1 foi maior na orelha direita (valor-p = 0,050), não sendo observada diferença significante entre os grupos tanto para os valores de latência quanto para os de amplitude dos componentes estudados. Conclusão: No que diz respeito ao PEATE clique, indivíduos com TEA apresentaram resultados sugestivos de alteração na via auditiva em tronco encefálico alto, indicando possíveis lesões ou disfunções do Sistema Nervoso Auditivo Central (SNAC). Com relação ao PEATE com estímulo de fala, pode-se concluir que a população de estudo apresentou codificação neural mais rápida da parte inicial do estímulo acústico (onset) quando comparada ao grupo com DT. Os resultados do PEALL não demonstraram alteração a nível cortical em indivíduos com TEA. Frente aos resultados obtidos, sugere-se novos estudos que realizem os exames eletrofisiológicos de curta e longa latência com um número maior de participantes / Introduction: Individuals with Autism Spectrum Disorder (ASD), showed issues in social interactions, communication and behavior, and it is also possible to present impaired cognitive and language skills. Taking into account the knowledge about the peripheral and central hearing, it highlights importance of the complete audiological evaluation, in particular, the evaluation of the Central Auditory Nervous System in this population, in diagnosis and during the therapeutic process. Aim: To characterize Brainstem Evoked Response Auditory (BERA) with click and speech stimuli and Long-Latency Auditory Evoked Potential (LLAEP) with tone burst and speech stimuli, in individuals with ASD. Methods: 30 children aged between seven and 12 years, of both sexes participated in this study, 15 of the study group (SG - children diagnosed with ASD) and 15 of the control group (CG - children with typical development - TD), matched by sex and age. The following tests were accomplished: anamnesis, meatoscopy, basic audiological evaluation (tonal audiometry, logoaudiometry and imitanciometry), and electrophysiological evaluation of hearing (BERA with click and speech stimulus and LLAEP with tone burst and speech stimulus). All the exams were done at the Teaching and Research Center of the Department of Physical Therapy, Speech and Hearing Therapy and Occupational Therapy, Faculty of Medicine, University of São Paulo. Results: In BERA with click stimulus, the average latency value of the wave I was higher for the right ear in all groups (p-value = 0.037), this occurring the ear effect. It was also observed that the III-V interpeak is higher in the TEA group than TD group (p-value = 0.046). In BERA with speech stimulus, an absolute latency of wave V was smaller than the ASD group when compared to the group with TD (p-value = 0.011). In the LLAEP, for the tone burst stimulus as well as for the speech stimulus, the latency of the N1 component was higher in the right ear (p-value = 0.050), between the groups were not being observed meaning differences for the latency values as for the amplitude values of the studied components. Conclusion: In relation to the BERA click, TEA group presented suggestive results of impairment in the auditory pathway, upper brainstem part, indicating possible lesions or dysfunctions of the Central Auditory Nervous System (CANS). With regard to BERA speech, can be concluded that the study population presented faster neural encoding of the initial part in the acoustic stimulus (onset) when compared with the TD group. The results of the LLAEP didn\'t show any changes in a cortical level of TEA group. From the results, we suggest new studies with BERA and LLAEP with a larger number of participants

Attention Deficit Hyperactivity Disorder (ADHD) is a disorder affecting cognitive control. These functions are important to achieve goals when different actions need to be executed in close succession. This type of multi-component behavior, which often further requires the processing of information from different modalities, is important for everyday activities. Yet, possible changes in neurophysiological mechanisms have not been investigated in adolescent ADHD. We examined N = 31 adolescent ADHD patients and N = 35 healthy controls (HC) in two Stop-Change experiments using either uni-modal or bi-modal stimuli to trigger stop and change processes. These stimuli were either presented together (SCD0) or in close succession of 300 milliseconds (SCD300). Using event-related potentials (ERP), EEG data decomposition and source localization we analyzed neural processes and functional neuroanatomical correlates of multicomponent behavior. Compared to HCs, ADHD patients had longer reaction times and higher error rates when Stop and Change stimuli were presented in close succession (SCD300), but not when presented together (SCD0). This effect was evident in the uni-modal and bi-modal experiment and is reflected by neurophysiological processes reflecting response selection mechanisms in the inferior parietal cortex (BA40). These processes were only detectable after accounting for intra-individual variability in neurophysiological data; i.e. there were no effects in standard ERPs. Multi-component behavior is not always deficient in ADHD. Rather, modulations in multi-component behavior depend on a critical temporal integration window during response selection which is associated with functioning of the inferior parietal cortex. This window is smaller than in HCs and independent of the complexity of sensory input.

This master´s thesis deals with processing and analysis of data, acquired from experimental examination performed with functional magnetic resonance imaging technique. It is an oddball type experimental task and its goal is an examination of cognitive functions of the subject. The principles of functional magnetic resonance imaging, possibilities of experimental design, processing of acquired data, modeling of a response of organism and statistical analysis are described in this work. Furthermore, particular parts of preprocessing and analysis are carried out using real data set from experiment. The main goal of this work is suggestion and realization of model, which enables advanced categorization of stimuli, considering the type of previous rare stimulus and the number of frequent stimuli within them. With its in-depth categorization, this model enables detail exploration of cerebral processes, associated mainly with attention, memory, expectancy or cognitive closure. The second point of that work is an evaluation of models of hemodynamic response, which are applied in statistical analysis of data from fMRI experiment. Comparison of basis functions, the models of hemodynamic response to experimental stimulation used for general linear model, is performed in this work. The result of this comparison is an evaluation of detection efficiency of activated voxels, false positivity rate and computational and user difficulty.

<p><b>Purpose:</b> Children with speech sound disorder (SSD) mispronounce more speech sounds than is typical for their age and a growing body of research suggests that a deficit in speech perception abilities contributes to development of the disorder. However, little work has been done to characterize the neurophysiological processes indexing speech perception deficits in SSD. The primary aim of the current study was to compare the neural activity underlying speech perception in young children with SSD and typical development (TD).</p><p><b>Method</b>: Twenty-eight children ages 4;1-6;0 participated in the current study. Event-related potentials (ERPs) were recorded while children completed a speech perception task which included phonetic (speech sound) and lexical (meaning) matches and mismatches. Groups were compared on their judgment accuracy for matches and mismatches as well as the mean amplitude of the Phonological Mapping Negativity (PMN) and N400 ERP components.</p><p><b>Results</b>: Children with SSD demonstrated lower judgment accuracy across the phonetic and lexical conditions compared to peers with TD. The ERPs elicited by lexical matches and mismatches did not distinguish the groups. However, in the phonetic condition, the SSD group exhibited a more consistent left lateralized PMN effect and a delayed N400 effect over frontal sites compared to the TD group.</p><p><b>Conclusions</b>: These findings provide some of the first evidence of a delay in the neurophysiological processing of phonological information for young children with SSD compared to their peers with TD. This delay was not present for the processing of lexical information, indicating a unique difference between children with SSD and TD related to speech perception of phonetic errors.</p>

Le but principal de cette thèse était de mieux comprendre la relation entre le déploiement de l’attention visuo-spatiale et la réponse lors de la recherche visuelle. Nous avons combiné des mesures de chronométrie mentale (les temps de réponse; TR) et d’électrophysiologie, permettant le suivi du décours temporel des évènements et la séparation des processus en sous-phases. Trois études ont été effectuées. Dans les deux premières études, la N2pc, un potentiel relié à un événement (PRE), a été utilisé comme indice électrophysiologique de l’attention visuelle vers un stimulus latéral lors d’une tâche de recherche visuelle ayant une cible facilement repérable (qui saute aux yeux) parmi des distracteurs. Cette composante est caractérisée, en électrophysiologie, par une plus grande négativité environ 200 ms suivant la présentation de la stimulation aux sites postérieurs et controlatéraux du champ visuel ciblé. Dans la première étude, la relation entre la composante N2pc et la réponse a été examinée. Pour ce faire, les données électrophysiologiques ont été scindées selon le TR médian. La N2pc était plus ample pour les essais et les participants plus rapides comparés à ceux qui étaient plus lents, suggérant qu’un déploiement attentionnel plus efficace (N2pc plus ample) avait accéléré les processus subséquents (TR plus court). Dans l’étude 2, le traitement depuis le moment du déploiement attentionnel jusqu’à la réponse a été élucidé en examinant le déclenchement de la N2pc par rapport à la réponse et non au stimulus (ce qui est plus utilisé dans les paradigmes classiques). Nous avons été les premiers à utiliser la RLpcN (response-locked posterior contralateral negativity), composée de la composante N2pc et la SPCN (une composante suivant la N2pc reflétant le traitement en mémoire visuelle à court terme). Les résultats ont démontré une augmentation du temps entre le début de la RLpcN et la réponse pour les TR plus lents, reflétant un traitement plus long suivant le déploiement de l’attention spatiale. Nous avons par la suite utilisé cette composante (la RLpcN) pour étudier la recherche visuelle difficile (Étude 3), où la cible n’était pas facilement identifiable parmi des distracteurs, à l’aide de manipulations expérimentales modulant la RLpcN, soit le nombre d’items et de réponses possibles. Plus il y avait d’items dans le champ visuel ou de possibilités de réponses, plus longue était la durée entre le début de la RLpcN et la réponse, démontrant ainsi qu’il est possible d’observer l’activité associée avec les processus sous-jacents à ces manipulations lors d’une recherche difficile. En somme, nous avons montré (1) qu’un déploiement attentionnel plus efficace accélère les processus subséquents, (2) que le traitement déterminant les TR se produit, en majorité, suivant le déploiement de l’attention et, enfin, (3) qu’il est possible d’identifier des marqueurs électrophysiologiques de la sélection de la cible ainsi que de la réponse lors d’une recherche difficile. Dans l’ensemble, les résultats des études constituant la présente thèse vont au-delà des études électrophysiologiques de recherche visuelle typiques, qui utilisent généralement des cibles qui sautent aux yeux, et élucident le décours temporel du traitement lors de recherches plus complexes. / The overarching thesis was to understand better the relationship between the deployment of visual spatial attention and the eventual response during visual search. We combined mental chronometry with electrophysiological measures, allowing us to track the temporal sequence of events and bisect processing into sub-phases. The two first studies used the N2pc, an event-related potential (ERP) component, as an electrophysiological marker of visual attention to laterally presented stimuli using a pop-out (i.e., the target stands out) visual search task. The N2pc is characterised by an enhanced negativity emerging around 200 ms after the display onset at posterior sites contralateral to the attended visual field. In Study 1, we first evaluated the relationship between the N2pc component and the moment of response. Electrophysiological data were split according to the response time (RT) median. The N2pc was larger for both fast compared with slow trials and participants, suggesting that a more efficient deployment of attention (larger N2pc) sped up downstream processing (shorter RTs). In Study 2, processing from the deployment of attention to the response was elucidated by examining N2pc onset relative to the response instead of to the display onset. We pioneered the use of the RLpcN (response-locked contralateral negativity), composed of the N2pc and the SPCN (a component following the N2pc and reflecting processing of task-relevant stimuli in visual short-term memory). Importantly, more time passed between RLpcN onset and the response for longer RTs, reflecting more processing time following the onset of visual spatial attention. We then used this component to study difficult search (Study 3), where the target was not easily located, using experimental manipulations designed to modulate the RLpcN. We showed that when there were more items present in the visual field or response selection was more difficult, there was a longer duration between RLpcN onset and the response, demonstrating that it is possible to observe activity associated with specific processes during difficult visual search. In summary, we provide evidence that (1) a more efficient deployment of attention speeds up downstream processing, (2) processing determining RTs occurs, in majority, following the deployment of attention, and (3) it is possible to identify electrophysiological markers of target and response selection during difficult search. Together, the results of these experiments go beyond typical electrophysiological experiments of visual search, which use pop-out targets, and elucidate the time course of processing during more complex search.

La présente thèse utilise la technique des potentiels évoqués afin d’étudier les méchanismes neurocognitifs qui sous-tendent la compréhension de la phrase. Plus particulièrement, cette recherche vise à clarifier l’interaction entre les processus syntaxiques et sémantiques chez les locuteurs natifs et les apprenants d’une deuxième langue (L2). Le modèle “syntaxe en premier” (Friederici, 2002, 2011) prédit que les catégories syntaxiques sont analysées de façon précoce: ce stade est reflété par la composante ELAN (Early anterior negativity, Négativité antérieure gauche), qui est induite par les erreurs de catégorie syntaxique. De plus, ces erreurs semblent empêcher l’apparition de la composante N400 qui reflète les processus lexico-sémantiques. Ce phénomène est défini comme le bloquage sémantique (Friederici et al., 1999). Cependant, la plupart des études qui observent la ELAN utilisent des protocoles expérimentaux problématiques dans lesquels les différences entre les contextes qui précèdent la cible pourraient être à l’origine de résultats fallacieux expliquant à la fois l’apparente “ELAN” et l’absence de N400 (Steinhauer & Drury, 2012). La première étude rééevalue l’approche de la “syntaxe en premier” en adoptant un paradigme expériemental novateur en français qui introduit des erreurs de catégorie syntaxique et les anomalies de sémantique lexicale. Ce dessin expérimental équilibré contrôle à la fois le mot-cible (nom vs. verbe) et le contexte qui le précède. Les résultats récoltés auprès de locuteurs natifs du français québécois ont révélé un complexe N400-P600 en réponse à toutes les anomalies, en contradiction avec les prédictions du modèle de Friederici. Les effets additifs des manipulations syntaxique et sémantique sur la N400 suggèrent la détection d’une incohérence entre la racine du mot qui avait été prédite et la cible, d’une part, et l’activation lexico-sémantique, d’autre part. Les réponses individuelles se sont pas caractérisées par une dominance vers la N400 ou la P600: au contraire, une onde biphasique est présente chez la majorité des participants. Cette activation peut donc être considérée comme un index fiable des mécanismes qui sous-tendent le traitement des structures syntagmatiques. La deuxième étude se concentre sur les même processus chez les apprenants tardifs du français L2. L’hypothèse de la convergence (Green, 2003 ; Steinhauer, 2014) prédit que les apprenants d’une L2, s’ils atteignent un niveau avancé, mettent en place des processus de traitement en ligne similaires aux locuteurs natifs. Cependant, il est difficile de considérer en même temps un grand nombre de facteurs qui se rapportent à leurs compétences linguistiques, à l’exposition à la L2 et à l’âge d’acquisition. Cette étude continue d’explorer les différences inter-individuelles en modélisant les données de potentiels-évoqués avec les Forêts aléatoires, qui ont révélé que le pourcentage d’explosition au français ansi que le niveau de langue sont les prédicteurs les plus fiables pour expliquer les réponses électrophysiologiques des participants. Plus ceux-ci sont élevés, plus l’amplitude des composantes N400 et P600 augmente, ce qui confirme en partie les prédictions faites par l’hypothèse de la convergence. En conclusion, le modèle de la “syntaxe en premier” n’est pas viable et doit être remplacé. Nous suggérons un nouveau paradigme basé sur une approche prédictive, où les informations sémantiques et syntaxiques sont activées en parallèle dans un premier temps, puis intégrées via un recrutement de mécanismes contrôlés. Ces derniers sont modérés par les capacités inter-individuelles reflétées par l’exposition et la performance. / The present thesis uses event-related potentials (ERPs) to investigate neurocognitve mechanisms underlying sentence comprehension. In particular, these two experiments seek to clarify the interplay between syntactic and semantic processes in native speakers and second language learners. Friederici’s (2002, 2011) “syntax-first” model predicts that syntactic categories are analyzed at the earliest stages of speech perception reflected by the ELAN (Early left anterior negativity), reported for syntactic category violations. Further, syntactic category violations seem to prevent the appearance of N400s (linked to lexical-semantic processing), a phenomenon known as “semantic blocking” (Friederici et al., 1999). However, a review article by Steinhauer and Drury (2012) argued that most ELAN studies used flawed designs, where pre-target context differences may have caused ELAN-like artifacts as well as the absence of N400s. The first study reevaluates syntax-first approaches to sentence processing by implementing a novel paradigm in French that included correct sentences, pure syntactic category violations, lexical-semantic anomalies, and combined anomalies. This balanced design systematically controlled for target word (noun vs. verb) and the context immediately preceding it. Group results from native speakers of Quebec French revealed an N400-P600 complex in response to all anomalous conditions, providing strong evidence against the syntax-first and semantic blocking hypotheses. Additive effects of syntactic category and lexical-semantic anomalies on the N400 may reflect a mismatch detection between a predicted word-stem and the actual target, in parallel with lexical-semantic retrieval. An interactive rather than additive effect on the P600 reveals that the same neurocognitive resources are recruited for syntactic and semantic integration. Analyses of individual data showed that participants did not rely on one single cognitive mechanism reflected by either the N400 or the P600 effect but on both, suggesting that the biphasic N400-P600 ERP wave can indeed be considered to be an index of phrase-structure violation processing in most individuals. The second study investigates the underlying mechanisms of phrase-structure building in late second language learners of French. The convergence hypothesis (Green, 2003; Steinhauer, 2014) predicts that second language learners can achieve native-like online- processing with sufficient proficiency. However, considering together different factors that relate to proficiency, exposure, and age of acquisition has proven challenging. This study further explores individual data modeling using a Random Forests approach. It revealed that daily usage and proficiency are the most reliable predictors in explaining the ERP responses, with N400 and P600 effects getting larger as these variables increased, partly confirming and extending the convergence hypothesis. This thesis demonstrates that the “syntax-first” model is not viable and should be replaced. A new account is suggested, based on predictive approaches, where semantic and syntactic information are first used in parallel to facilitate retrieval, and then controlled mechanisms are recruited to analyze sentences at the interface of syntax and semantics. Those mechanisms are mediated by inter-individual abilities reflected by language exposure and performance.

The studies investigated the impact of predictive visual information about the pitch and location of a forthcoming sound on the sound processing. In Symbol-to-Sound matching paradigms, symbols induced predictions of particular sounds. The brain’s error signals (IR and N2b components of the event-related potential) were measured in response to occasional violations of the prediction, i.e. when a sound was incongruent to the corresponding symbol. IR and N2b index the detection of prediction violations at different levels, IR at a sensory and N2b at a cognitive level. Participants evaluated the congruency between prediction and actual sound by button press. When the prediction referred to only the pitch or only the location feature (Exp. 1), the violation of each feature elicited IR and N2b. The IRs to pitch and location violations revealed differences in the in time course and topography, suggesting that they were generated in feature-specific sensory areas. When the prediction referred to both features concurrently (Exp. 2), that is, the symbol predicted the sound´s pitch and location, either one or both predictions were violated. Unexpectedly, no significant effects in the IR range were obtained. However, N2b was elicited in response to all violations. N2b in response to concurrent violations of pitch and location had a shorter latency. We conclude that associative predictions can be established by arbitrary rule-based symbols and for different sound features, and that concurrent violations are processed in parallel. In complex situations as in Exp. 2, capacity limitations appear to affect processing in a hierarchical manner. While predictions were presumably not reliably established at sensory levels (absence of IR), they were established at more cognitive levels, where sounds are represented categorially (presence of N2b).