Introdução: Plasticidade auditiva refere-se a mudanças que ocorrem no sistema sensorial responsável pela transmissão da informação acústica. A plasticidade do sistema nervoso auditivo central está relacionada a capacidade de adaptação através da reintrodução de estímulos por meio de aparelhos de amplificação sonora ou implante coclear. Essas mudanças são observadas a partir do desempenho de pacientes com o uso do aparelho de amplificação sonora, e podem ser verificadas por meio dos potenciais evocados auditivos de longa latência. Objetivo: caracterizar os Potenciais Evocados Auditivos de Longa Latência (PEALL) em adultos e idosos com perda auditiva neurossensorial, verificando os efeitos da estimulação auditiva por meio da comparação destes potenciais pré e pós adaptação do Aparelho de Amplificação Sonora Individual (AASI). Metodologia: Participaram deste estudo 15 indivíduos adultos e idosos, de ambos os gêneros, de 55 a 85 anos de idade, com perda auditiva neurossensorial de grau leve a moderado com simetria entre as orelhas, sem experiência prévia com qualquer tipo de dispositivo de amplificação sonora. Os indivíduos foram encaminhados pelas empresas de aparelho auditivo WIDEX, Audibel e o Espaço Reouvir, tratando-se de novos usuários de AASI. Os PEALL foram realizados nas condições com e sem AASI, a 60 e 75 dBnNA em campo sonoro, em dois momentos: primeira avaliação realizada até uma semana após a adaptação do AASI e a segunda avaliação realizada após 6 meses da adaptação do AASI. Resultados: Na comparação da primeira avaliação com a segunda avaliação, na condição sem AASI a 60 dBnNA, observou-se diferença estatisticamente significante na latência do componente P1 (p-valor= 0,034). Na condição sem AASI a 75 dBnNA, observou-se diferença estatisticamente significante para a latência do componente P300 (p-valor 0,031) e para a amplitude P2N2 (p-valor 0,024), com diminuição da latência e aumento da amplitude na segunda avaliação. Por sua vez, na comparação da primeira avaliação com a segunda avaliação, na condição com AASI a 75 dBnNA, obteve-se uma diferença estatisticamente significante na latência do componente N2 (p-valor 0,009) e na amplitude P2N2 (p-valor 0,024), com aumento da amplitude na segunda avaliação. Evidenciou-se, também, diferença significante na amplitude P1N1 (p-valor 0,024) na condição com AASI a 60 dBnNA. Conclusão: Os PEALL com estímulo de fala demonstraram ser um importante procedimento para ser utilizado na prática clínica, visando monitorar a plasticidade neuronal do Sistema Nervoso Auditivo Central frente à estimulação auditiva (uso de AASI), em adultos e idosos com perda auditiva neurossensorial de grau leve a moderado / Introduction: Auditory plasticity refers to changes that occur in the sensory system responsible for the transmission of acoustic information. The plasticity of the central auditory nervous system is related to the capacity of adaptation through the reintroduction of stimuli of sound amplification devices or cochlear implants. These changes are observed from the performance of patients with the use of the sound amplification apparatus, and can be verified by long-latency auditory evoked potentials. Purpose: To characterize long latency auditory evoked potentials (LLAEP) in adults with sensorineural hearing loss, verifying the effects of auditory stimulation by comparing these before and after adaptation potentials of the Individual Sound Amplification (AASI). Methodology: Fifteen adult and elderly individuals of both genders, aged 55 to 85 years, with mild to moderate sensorineural hearing loss with symmetry between the ears, without prior experience with any type of sound amplification device. The subjects were referred by hearing aid companies WIDEX, Audibel and Espaço Reouvir, in the case of new hearing aids users. The LLAEP were performed in the conditions with and without AASI, at 60 and 75 dBnNA in sound field, in two moments: first evaluation performed up to one week after AASI adaptation and the second evaluation performed after 6 months of AASI adaptation. Results: In the comparison of the first evaluation with the second evaluation, in the condition without AASI at 60 dBnNA, a statistically significant difference was observed in the latency of the P1 component (p-value = 0.034). In the condition without AASI at 75 dBnNA, a statistically significant difference was observed for the latency of the P300 component (p-value 0.031) and for the P2N2 amplitude (p-value 0.024), with latency decrease and amplitude increase in the second evaluation. In the comparison of the first evaluation with the second evaluation, in the condition with AASI at 75 dBnNA, there was a statistically significant difference in the latency of the N2 component (p-value 0.009) and in the P2N2 amplitude (p-value 0.024) , With amplitude increase in the second evaluation. There was also a significant difference in P1N1 amplitude (p-value 0.024) in the condition with AASI at 60 dBnNA. Conclusion: The LLAEP was an important procedure to be used in clinical practice, aiming to monitor the neural plasticity of the Central Auditory Nervous System in front of auditory stimulation (hearing aids use) in adults and elderly patients with mild to moderate sensorineural hearing loss of amplification and the importance of neural plasticity of the Central Auditory Nervous System

Objective: Attention Bias Modification Training (ABMT) for anxiety aims to train attention away from threatening stimuli and toward neutral stimuli. Although ABMT shows promising anxiety reduction effects in children and adolescents, no study has examined its influence on neural indicators of attention measured using event-related potentials (ERPs) in children or adolescents (i.e., youths). The present study examined the influence of ABMT on the P1, N170, P2 and P3 ERP components during completion of the emotional faces dot probe task in youths with anxiety disorders who failed to respond to cognitive behavioral therapy. Method: Thirty youths (M age = 11.97, SD = 2.89) with primary DSM-IV-TR anxiety disorders completed the dot probe task while undergoing electroencephalogram (EEG) to obtain ERPs before, immediately after, and eight weeks after eight sessions of either ABMT (n = 14) or a control task regimen (CT), (n = 16). Results: At post-treatment, statistically significant effects were found for P1 and P3 mean amplitudes: P1 was significantly higher during trials showing neutral-neutral (NN) face pairs in the ABMT arm than in the CT arm; P3 was significantly higher during trials showing NN face pairs than during trials showing neutral-threat (NT) face pairs in the ABMT arm, but not the CT arm. At eight-week follow-up, participants in both arms showed significantly higher (more negative) N170 responses for NN trials than for NT trials. Conclusions: Attention Bias Modification Treatment led to increases in neural processing of neutral stimuli in early and late stage attentional processing, as measured by the P1 and P3 components, respectively. These components during the dot probe task are promising neural markers of ABMT’s effects on attentional processing in youth with anxiety disorders.

L’addiction à l’alimentation (AA) est un concept ancien, mais encore sujet de controverses qui toucherait 18 à 24 % des obèses. Dans cette thèse, nous nous sommes intéressés aux intrications entre régulations du comportement alimentaire, addiction et AA, afin de mieux comprendre les mécanismes liés à la désinhibition de la prise alimentaire. Notre travail a conduit à plusieurs résultats : 1) Une revue de la littérature a permis de montrer l’existence d’interaction étroite entre les niveaux de régulation du comportement alimentaire et comment AA pourrait en être un exemple de dérégulation. 2) Une étude de cohorte a permis de démontrer l’existence de caractéristiques cliniques communes entre addictions et AA et celle d’un probable transfert d’addiction de la nicotine vers l’alimentation. 3) Sur le plan expérimental, nous avons montré qu’il existe des perturbations des ondes P300 et N200, dans l’obésité et la désinhibition alimentaire, proches de celles observées dans les addictions. 4) Enfin, nos résultats suggèrent le rôle potentiel de la ghréline comme marqueur de risque de trouble du comportement alimentaire. Ce travail ouvre des perspectives sur le plan expérimental, avec la suggestion de groupes contrôles plus pertinents ; cliniques, avec la création d’un potentiel test de dépistage rapide ; thérapeutiques, avec la mise en place d’un essai thérapeutique par tDCS / Food addiction (FA) is an old concept, but still subject to controversy. It affects 18 to 24% of obese people. In this thesis, we are interested in overlaps between food behavior regulation, addiction and FA, in order to better understand the mechanisms linked to food intake disinhibition. Our work leads to several results: 1) A review of the literature has shown the existence of close interaction between eating behavior regulation levels and how FA could be an example of their disturbance. 2) A cohort study demonstrated the existence of common clinical features between addiction and FA and a probable addiction transfer from nicotine to food. 3) From an experimental point of view, we have shown that there are disturbances of P300 and N200 ERP, in obesity and food disinhibition, close to those observed in addictions. 4) Finally, our results suggest the potential role of ghrelin as a marker for eating disorders increased risk. This work opens experimental perspectives, with the suggestion of more relevant control groups; clinical perspectives, with the creation of a screening tool; therapeutics perspectives, with the establishment of a therapeutic trial by tDCS

This thesis study focuses on the realization of an online cue based Motor Imagery (MI) Brain Computer Interface (BCI). For this purpose, some signal processing and classification methods are investigated. Specifically, several time-spatial-frequency methods, namely the Short Time Fourier Transform (STFT), Common Spatial Frequency Patterns (CSFP) and the Morlet Transform (MT) are implemented on a 2-class MI BCI system. Distinction Sensitive Learning Vector Quantization (DSLVQ) method is used as a feature selection method. The performance of these methodologies is evaluated with the linear and nonlinear Support Vector Machines (SVM), Multilayer Perceptron (MLP) and Naive Bayesian (NB) classifiers. The methodologies are tested on BCI Competition IV dataset IIb and an average kappa value of 0.45 is obtained on the dataset. According to the classification results, the algorithms presented here obtain the 4th level in the competition as compared to the other algorithms in the competition. Offline experiments are performed in METU Brain Research Laboratories and Hacettepe Biophysics Department on two subjects with the original cue-based MI BCI paradigm. Average prediction accuracy of the methods on a 2-class BCI is evaluated to be 76.26% in these datasets. Furthermore, two online BCI applications are developed: the ping-pong game and the electrical wheelchair control. For these applications, average classification accuracy is found to be 70%. During the offline experiments, the performance of the developed system is observed to be highly dependent on the subject training and experience. According to the results, the EEG channels P3 and P4, which are considered to be irrelevant with the motor imagination, provided the best classification performance on the offline experiments. Regarding the observations on the experiments, this process is related to the stimulation mechanism in the cue based applications and consequent visual evoking effects on the subjects.

Objective: The aim of the present study was to investigate the mechanics with which older adults activate and access different subdomains of their mental lexicons during word retrieval for picture naming. Method: Data were analyzed for 12 aging, native English speakers who performed a picture-word priming task. The auditory probe words were presented in the following conditions in relation to the picture stimuli: Identically related, strongly semantically related, weakly semantically related, strongly phonologically related, weakly phonologically related, semantically related to the strong phonological relative of the target picture label, or phonologically-related to the strong semantic relative of the target picture label. Event related potentials were used to measure picture-word priming effects. Results: Three main results were observed. First, our healthy aging adult participants evidenced strong activation of whole-word phonological representations as well as rhyme representations of target picture labels, but weakened activation of initial phoneme information. Second, they processed semantic information robustly. Finally, our participants appeared to experience phonological competition when accessing target picture labels. Conclusion: Results from this study suggest that healthy aging adults maintain efficient access to whole-word phonological representations, rhyme representations, and conceptual-semantic representations of target picture labels. However, in line with previously-reported findings, they do seem to evidence limited activation of initial phonological information on the path to picture naming.

No description available.

L'objectif de cette thèse est d'étudier le développement du système lexico-sémantique chez les enfants monolingues et bilingues. La question posée est la suivante : quand et comment les significations des mots commencent à être reliées entre elles et à s'intégrer dans un système sémantique interconnecté. Dans un premier temps, trois études ont été menées chez des enfants monolingues français. L'Etude 1, a pour but d'observer si les mots sont organisés selon des liens taxonomiques (e.g., cochon - cheval). L'Etude 2 explore si l'effet d'amorçage sémantique est sous-tendu par des mécanismes cognitifs, comme les processus d'activation automatique et contrôlé. Puis enfin, l'Etude 3 observe si les mots sont organisés en fonction de leur distance de similarité sémantique (e.g., vache - mouton versus vache - cerf). Dans un deuxième temps, deux études ont été conduites chez des enfants apprenant deux langues simultanément. L'Etude 4 vise à déterminer si les mots sont taxonomiquement liés dans chacune des langues. L'Etude 5 explore si les mots présentés dans une langue activent leurs représentations sémantiques dans l'autre langue et vice versa. Dans le but de répondre à ces questions, le traitement lexico-sémantique a été étudié en utilisant deux techniques : l'eye-tracking et les potentiels évoqués (PEs). Ces deux techniques enregistrent lors de la présentation des mots des réponses comportementales (Etude 3) et neuronales (Etude 1, 2, 4 et 5) de haute résolution temporelle. Les Etudes 1 et 2 montrent que chez les monolingues les mots sont liés taxonomiquement à l'âge de 18 et 24 mois. Durant le développement du langage, les deux processus d'activation automatique et contrôlé sont impliqués dans le traitement des mots (Etude 2). L'Etude 3 montre qu'à 24 mois, les mots sont organisés dans le système lexico-sémantique en développement selon la distance des similarités sémantiques. L'Etude 4 montre que chez les enfants bilingues, le traitement sémantique ne diffère pas selon les deux langues, mais la topographie des PEs varie selon la langue traitée. L'Etude 5 montre que les mots présentés dans une langue activent leurs représentations sémantiques dans la deuxième langue et vice versa. Toutefois, la topographie des PEs est modulée selon la direction de traduction. Ces résultats suggèrent que l'acquisition de deux langues, bien qu'elle soit très précoce, requière deux ressources neuronales bien distinctes, sous-tendant ainsi le traitement lexico-sémantique des langues dominante et non-dominante. / The present doctoral research explored the developing lexical-semantic system in monolingual and bilingual toddlers. The question of how and when word meanings are first related to each other and become integrated into an interconnected semantic system was investigated. Three studies were conducted with monolingual French learning children which aimed at exploring how words are organized, that is, according to taxonomic relationships (e.g., pig - horse) and to semantic similarity distances between words (e.g., cow - sheep versus cow - deer), and whether cognitive mechanisms, such as automatic activation and controlled processes, underlie priming effects. An additional two studies conducted with children learning two languages simultaneously, aimed at determining, first, whether taxonomically related word meanings, in each of the two languages, are processed in a similar manner. The second goal was to explore whether words presented in one language activate words in another language, and vice versa. In an attempt to answer these questions, lexical-semantic processing was explored by two techniques: eye-tracking and event-related potentials (ERPs) techniques. Both techniques provide high temporal resolution measures of word processing but differ in terms of responses. Eye-movement measurements (Study III) reflect looking preferences in response to spoken words and their time-course, whereas ERPs reflect implicit brain responses and their activity patterns (Study I, II, IV, and V). Study I and II revealed that words are taxonomically organized at 18 and 24-month-olds. Both automatic and controlled processes were shown to be involved in word processing during language development (Study II). Study III revealed that at 24-month-olds, categorical and feature overlap between items underpin the developing lexical-semantic system. That is, lexical-items in each semantic category are organized according to graded similarity distances. Productive vocabulary skills influenced word recognition and were related to underlying cognitive mechanisms. Study IV revealed no differences in terms of semantic processing in the bilinguals¿ two languages, but the ERP distribution across the scalp varied according to the language being processed. Study V showed that words presented in one language activate their semantic representations in the second language and the other way around. The distribution of the ERPs depended, however, on the direction of translation. The results suggest that even early dual language experience yields distinct neural resources underlying lexical-semantic processing in the dominant and non-dominant languages during language acquisition.

Il apparaît, suite aux résultats de plusieurs études comportementales et d’imagerie cérébrale, que les hormones gonadiques peuvent moduler le fonctionnement cérébral chez la femme. Les asymétries cérébrales fonctionnelles (ACFs), en particulier, changeraient en fonction du niveau de progestérone et d’œstrogène. On a également observé que lorsque le taux d’œstrogène est bas, les performances aux tâches impliquant l’hémisphère droit sont améliorées. Par contre, les preuves de l’action physiologique de ces deux hormones sur le cerveau ne sont pas très nombreuses. Le peu d’études d’électrophysiologie cognitive qui ont porté sur les effets du cycle menstruel ont rapporté que la composante P300 y serait sensible. Aucune n’a cependant utilisé une tâche d’habileté spatiale ou de rotation mentale qui sont connues pour impliquer davantage l’hémisphère droit. Le but de la présente étude est de documenter les changements électrocorticaux reliés aux variations hormonales lors d’une tâche de rotation mentale. Notre hypothèse de départ est que le taux d’œstrogène influencera l’activité électrocorticale et la latéralisation. Les potentiels évoqués cognitifs ont été comparés chez les mêmes femmes (n=12) lors d’une tâche de rotation mentale, répétée à deux périodes du cycle menstruel. Nos résultats démontrent que la condition de rotation induit une latéralisation de l’activité pariétale, vers l’hémisphère gauche, quand le niveau d’œstrogène est bas. Par contre, lorsque le niveau d’œstrogène est élevé, il n’y a aucune latéralisation. Par ailleurs, nous avons observé une augmentation de l’amplitude de la P300 lors du niveau oestrogénique élevé. En conclusion, les fluctuations oestrogéniques du cycle menstruel ont un impact sur la latéralisation de l’activité électrocorticale, lors d’un effort de rotation mentale. / After many behavioral and some neuroimaging studies, it appears that the gonadic hormones can modulate the neuronal function of women's brain. In particular, the functional cerebral asymmetries can be affected by the level of progesterone and estrogens. It has been observed that when the level of estrogen is low, the performance at task that engages more the right hemisphere is enhanced. However, there is a lack of evidence for the physiological actions of these two hormones on the brain. The few event-related potential studies taking into account the menstrual cycle effects, had noticed that the component P300 can be affected. No electrophysiological study has used a mental rotation task or spatial ability tests which are known for their right hemisphere dominance. The aim of the present research is to document the effect of hormonal variations on the electrocortical activity, using a mental rotation task. Our hypothesis is that estrogen levels affect electrocortical activity and lateralization. The ERPs were compared in the same women (n = 12) during a mental rotation task, repeated over two periods of the menstrual cycle. Our results show a lateralization of the left parietal activity when estrogen levels are low and during the rotation. Whereas when the estrogen level is high, there is no lateralization. In addition, we observed an increase in the amplitude of P300 for this same high level. In conclusion, estrogens fluctuations associated with the menstrual cycle have an impact on the lateralization of electrocortical activity, when a mental rotation is needed.

L’influence de la couleur dans les mécanismes perceptuels et attentionnels a été étudiée. Quatre couleurs (le rouge, le vert, le bleu et le jaune) ont été calibrées individuellement à travers la technique heterochromatic flicker photometry. Suivant cela, les participants ont déployé leur attention à une cible (un cercle de couleur avec une ligne orientée). Les données électrophysiologiques ont été enregistrées pendant que les sujets performaient la tâche de recherche visuelle, et les analyses ont été basées sur les potentiels évoqués (PÉs). Trois composantes des PÉs ont été examinées : la posterior contralateral positivity (Ppc); la N2pc, reflétant le déploiement de l’attention visuo-spatiale et la temporal and contralateral positivity (Ptc). Des conditions dans lesquelles la cible était bleu ou rouge, lorsque comparées à des conditions avec une cible jaune ou verte suscitaient une N2pc plus précoce. Une amplitude plus élevée est aussi observée pour les cibles rouges pour les composantes Ppc et Ptc, reflétant une sélectivité pré-attentionelle. Ces résultats suggèrent de la prudence dans l’interprétation de données comparant des cibles de différentes couleurs dans des tâches de PÉs, et ce même lorsque les couleurs sont équiluminantes. / We investigated how target color affected behavioral and electrophysiological results in a visual search task. Perceptual and attentional mechanisms were tracked using the N2pc component of the event-related potential and other lateralized components. Four colors (red, green, blue, or yellow) were calibrated for each participant for luminance through heterochromatic flicker photometry and equated to the luminance of grey distractors. Each visual display contained 10 circles, 1 colored and 9 grey, each of which contained an oriented line segment. The task required deploying attention to the colored circle, which was either in the left or right visual hemifield. Three lateralized ERP components relative to the side of the lateral colored circle were examined: a posterior contralateral positivity (Ppc) prior to N2pc, the N2pc, reflecting the deployment of visual spatial attention, and a temporal and contralateral positivity (Ptc) following N2pc. Red or blue stimuli, as compared to green or yellow, had an earlier N2pc. Both the Ppc and Ptc had higher amplitudes to red stimuli, suggesting particular selectivity for red. The results suggest that attention may be deployed to red and blue more quickly than to other colors and suggests special caution when designing ERP experiments involving stimuli in different colors, even when all colors are equiluminant.

The successful execution of goal-directed movement requires the evaluation of many levels of errors. On one hand, the motor system needs to be able to evaluate ‘high-level’ errors indicating the success or failure of a given movement. On the other hand, as a movement is executed the motor system also has to be able to correct for ‘low-level’ errors - an error in the initial motor command or change in the motor command necessary to compensate for an unexpected change in the movement environment. The goal of the present research was to provide electroencephalographic evidence that error processing during motor control is evaluated hierarchically. The present research demonstrated that high-level motor errors indicating the failure of a system goal elicited the error-related negativity, a component of the event-related brain potential (ERP) evoked by incorrect responses and error feedback. The present research also demonstrated that low-level motor errors are associated with parietally distributed ERP component related to the focusing of visuo-spatial attention and context-updating. Finally, the present research includes a viable neural model for hierarchical error processing during motor control.