Nous proposons d'explorer électrophysiologiquement la question de l'accès au sens. Pour cela, nous nous intéressons particulièrement à deux ERPs. La composante N400 est classiquement associée à la prise en compte d'un contexte sémantique. La composante P600, moins explorée, est retrouvée lors de tâches syntaxiques, sémantiques ou non spécifiquement linguistiques. Nous avons décrit trois études électrophysiologiques en conditions naturelles de langage. La première étude nous a permis de valider l'usage de ce matériel original dans une population contrôle. Puis nous avons proposé le transfert clinique de ce protocole en conditions naturelles de langage auprès de patients souffrant de TAB (deuxième étude) et de schizophrénie (troisième étude, en cours). Nous avons retrouvé une composante N400 préservée dans les TAB, alors que les patients souffrant de schizophrénie présentent un profil ERP altéré, avec une compréhension perturbée des mots comme congruents au contexte sémantique. Après nous être interrogés sur la notion de transfert clinique, et la prudence nécessaire à l'interprétation de ces résultats en pratique clinique quotidienne, nous avons envisagé deux autres approches relatives à l'accès au sens. D'une part, nous avons repris un modèle linguistique issu des perspectives phénoménologique, structuraliste et morphodynamique, pour détailler un protocole expérimental en cours de réalisation, ainsi que des premiers résultats exploratoires obtenus en population contrôle. D'autre part, les données en première personne après entretien d'explicitation apportent une illustration subjective des phénomènes d'accès au sens mis en jeu dans les deux protocoles utilisés. / The aim of our projectwas to examine semantic access from an electrophysiological view. We specifically explored two Event-related Potentials (ERPs): N400, associated to semantic processing, and P600, associated to syntactic, semantic and non linguistic and general processes. In the first part of our project, we have explored these ERPs among healthy participants and psychiatric patients. People with schizophrenia exhibit thought and language disorders. In spite of common clinical manifestations with schizophrenia, patients with bipolar disorders (BDs) have rarely been assessed using neurolinguistic ERPs. We have conducted three electrophysiological studies in natural speech conditions. In the first study, we validated our original linguistic material among healthy participants. Then, in a clinical transfer perspective, we assessed manic patients suffering from BDs (second study) and patients with schizophrenia (third study, in preparation) using the same linguistic material. Our results support the hypothesis of a preserved N400 component in patients with BDs. On the contrary, preliminary results showed a disturbed N400 associated to congruent sentences among patients with schizophrenia.After discussing the limitations of the notion of clinical transfer and of our experimental studies, we also presented two alternative perspectives on speech comprehension. One the one hand, we described a linguistic model inherited from phenomenology, structuralism and morphodynamics. On the other hand, we reported first person data obtained through elicitation techniques. These experiential data enable us to better grasp semantic phenomena involved in our both experiments.

Gesichterkognition ist eine wichtige Fähigkeit für soziale Interaktionen. Obwohl große interindividuelle Unterschiede in der Gesichterkognition festgestellt wurden, gibt es bisher wenige Bestrebungen, diese Fertigkeit zu trainieren. In den vorliegenden Studien habe ich Trainingsverfahren für das Gesichtergedächtnis und die Geschwindigkeit der Gesichterkognition entwickelt und untersucht, welche auf dem Modell von Wilhelm et al. (2010) beruhen. In Studie 1 wurden Trainingseffekte bei gesunden Probanden mittleren Alters behavioral untersucht. Das Training des Gesichtergedächtnisses zeigte einen Trend zur Leistungsverbesserung in der trainierten Aufgabe. Das Training der Geschwindigkeit der Gesichterkognition verkürzte signifikant die Reaktionszeiten in allen Geschwindigkeitsaufgaben der Gesichterkognition, der Objektkognition sowie der mentalen Geschwindigkeit. Daher wird angenommen, dass das Geschwindigkeitstraining eine allgemeine Fähigkeit, komplexe visuelle Stimuli zu verarbeiten, beeinflusst hat. In Studie 2 wurden nach einem Re-Training die psychophysiologischen Grundlagen der trainingsbedingten Veränderungen untersucht. Das Geschwindigkeitstraining verkürzte zwar die Reaktionszeiten im Verlauf des Re-Trainings, jedoch unterschieden sich die beiden Trainingsgruppen nicht im folgenden Posttest. Die Auswertung der ereigniskorrelierten Potentiale wies auf eine Reduktion der strukturellen Repräsentationen aus dem Langzeitgedächtnis zur Erkennung von Individuen (N250r) durch das Geschwindigkeitstraining und auf eine Verstärkung der semantischen Verarbeitung von bekannten Gesichtern (N400) durch das Gedächtnistraining hin. Die vorliegende Arbeit zeigt die Plastizität der Verarbeitungsgeschwindigkeit für komplexe visuelle Stimuli auf. / Face cognition is a crucial skill for social interaction. Large individual differences in face cognition have been shown for healthy adults, suggesting that there might be a need for improvement, yet training of this ability has seldom been attempted. In the present studies, I developed and tested training procedures for face memory and for speed of face cognition, based on the model developed by Wilhelm et al. (2010). In Study 1, training effects were studied with healthy middle-aged participants at the behavioural level. Both training procedures enhanced performance over the course of the training. For facial speed, this improvement was significant as were the faster reaction times on all tasks for facial speed, for object speed, and for general processing speed. Thus, training of facial speed influenced a more general ability to process complex visual stimuli more quickly. Study 2 was conducted to investigate the psychophysiological underpinnings of training effects after a re-training. The facial speed training enhanced performance over the course of the re-training. In the post-test conducted directly after the re-training, the two groups did not differ in reaction times. Results within event-related components suggested that the facial speed training reduced the contributions of structural representations from long-term memory to identity recognition (N250r) and that face memory training enhanced the semantic processing of familiar faces (N400). This dissertation demonstrates the plasticity of the speed of processing complex visual stimuli. The versatility of the results and the limitations of the studies are discussed along with suggestions for future research.

Notre travail de thèse porte sur les troubles du langage et de la pensée rencontrés chez des personnes souffrant de trouble bipolaire mais aussi, à un moindre degré, chez des personnes présentant des traits de personnalité hypomaniaque. Afin d’explorer les processus sémantiques qui sous-tendent ces troubles, nous avons réalisé plusieurs études à l’aide d’une tâche de résolution d’ambiguïté sémantique couplée à l’enregistrement de l’activité cérébrale (EEG et IRMf) afin de repérer des marqueurs nous aidant à la compréhension des mécanismes sous-tendant l’expression clinique ou sub-clinique de certains symptômes du trouble bipolaire.Nos travaux montrent des difficultés d’inhibition sémantique dans les deux populations qui se traduisent, sur le plan électrophysiologique, par une réduction de l’amplitude de la composante N400 en condition d’inhibition sémantique, corrélée au score de Vitalité Sociale (traits de personnalité hypomaniaque) en population générale et au score d’hypomanie chez les patients bipolaires. Des activations cérébrales sont également corrélées à la présence de traits de personnalité hypomaniaque au niveau du gyrus frontal supérieur et du lobule pariétal inférieur. Ces régions sont activées également chez les patients bipolaires comparativement au groupe contrôle, ainsi que d’autres régions fronto-temporales latéralisées à droite. Nos résultats vont dans le sens d’une modification du processus d’inhibition sémantique observable chez les patients bipolaires et dès la présence de traits de personnalité hypomaniaque. Nos travaux, associés à la littérature, nous suggèrent que les modulations de la composante N400 ou que les activations fronto-pariéto-temporales retrouvées pourraient être des marqueurs transnosographiques correspondant à la dimension clinique des troubles du langage et de la pensée dans le cadre du spectre bipolaire, mais également dans d’autres pathologies telles que les troubles du spectre de la schizophrénie. / Our thesis explores the underlying mechanisms of thought and language disorders commonly observed in patients suffering from bipolar disorder, but also to a lesser degree, in people with hypomanic personality traits. To explore the underlying semantic processes, we conducted four studies with a semantic ambiguity resolution task coupled with event-related potentials recording and fMRI. Our aim was to identify biomarkers for a better comprehension of clinical or subclinical symptoms associated with bipolar disorder.Through our studies, we have shown difficulties to handle semantic inhibition in the two explored populations with, at an electrophysiological level, a reduced N400 amplitude during semantic inhibition process, correlated to Social Vitality score (hypomanic personality traits) in non-clinic population, and to hypomania score in bipolar patients. In the fMRI studies, activations of the superior frontal gyrus and of the inferior parietal lobule were correlated to hypomanic traits and were also found in bipolar patients when compared to the control group. Supplementary right fronto-temporal activations were observed in bipolar patients. Our results imply an impairment of the semantic inhibition process already present in people with bipolar disorders and people with hypomanic traits. These results combined with the existing literature suggest that N400 modulations and fronto-temporo-parietal activations found might be transnosographic biomarkers of thought and language disorders, in bipolar spectrum disorders but also in other disorders like schizophrenia spectrum disorders.

Within the field of computational linguistics, recent research has made successful advances in integrating word space models with n-gram models. This is of particular interest when a model that encapsulates both semantic and syntactic information is desirable. A potential application for this can be found in the field of psycholinguistics, where the neural response N400 has been found to occur in contexts with semantic incongruities. Previous research has found correlations between cloze probabilities and N400, while more recent research has found correlations between cloze probabilities and language models. This essay attempts to uncover whether or not a more direct connection between integrated models and N400 can be found, hypothesizing that low probabilities elicit strong N400 responses and vice versa. In an EEG experiment, participants read a text manipulated using a language model, and a text left unchanged. Analysis of the results shows that the manipulations to some extent yielded results supporting the hypothesis. Further results are found when analysing responses to the unchanged text. However, no significant correlations between N400 and the computational model are found. Future research should improve the experimental paradigm, so that a larger scale EEG recording can be used to construct a large EEG corpus. / Innom datalingvistikken har tidligere forskning gjort framsteg når det gjelder å kombinere ordromsmodeller og n-grammodeller. Dette er av spesiell interesse når det er ønskelig å ha en modell som fanger både semantisk og syntaktisk informasjon. Et potensielt bruksområde for en slik modell finnes innom psykolingvistikk, der en neural respons som kalles N400 vist seg å oppstå i kontekster med semantisk inkongruens. Tidligere forskning har oppdaget en sterk korrelasjon mellom cloze probabilities og N400, og nylig forskning har funnet korrelasjoner mellom cloze probabilities og sannsynlighetsmodeller fra datalingvistikk. Denne oppgaven har som mål å undersøke hvorvidt en mer direkte kobling mellom slike kombinerte modeller og N400 finnes, med hypotesen at lave sannsynligheter leder til store N400-responser og omvendt. Et antall forsøkspersoner leste en tekst manipulert ved hjelp av en slik modell, og en naturlig tekst, i et EEG-eksperiment. Resultatsanalysen viser at manipuleringene til en viss grad gav resultat som støtter hypotesen. Tilsvarende resultat ble funnet under resultatanalysen av responsene til den naturlige teksten. Ingen signifikante korrelasjoner ble oppdaget mellom N400 og den kombinerte modellen. Forbedringer for videre forskning involverer å blant annet forbedre eksperimentparadigmet slik at en storstilt EEG-inspilling kan gjennomføres for å konstruere en EEG-korpus. / Inom datalingvistiken har tidigare forskning visat lovande resultat vid kombinering av ordrumsmodeller och n-gramsmodeller. Detta är av speciellt intresse när det är önskvärt att ha en modell som fångar både semantisk och syntaktisk information. Ett potensielt användningsområde för en sådan modell finns inom psykolingvistiken, där en neural respons kallad N400 visat sig uppstå i situationer med semantisk inkongruens. Tidigare forskning har upptäckt en stark korrelation mellan cloze probabilities och N400, medan en nyare studie har upptäckt en korrelation mellan cloze probabilities och sannolikhetsmodeller från datalingvistiken. Denna uppsats har som mål att undersöka huruvida en mer direkt koppling mellan sådana kombinerade modeller och N400 finns, med hypotesen att låga sannolikheter leder till stora N400-responser och vice versa. Ett antal försökspersoner läste en text manipulerad med hjälp av en probabilistisk modell, och en naturlig text, i ett EEG-experiment. Resultatsanalysen visar att manipuleringen till viss grad gav resultat som stödjer hypotesen. Motsvarande resultat hittades under resultatanalysen av responserna till den naturliga texten. Inga signifikanta korrelationer blev upptäckta mellan N400 och den kombinerade modellen. Förbättringar för vidare forskning involverar bland annat att förbättra experimentparadigmet så att en storskalig EEG-inspelning kan genomföras för att konstruera en EEG-korpus.

Cochlea-Implantate sind Neuroprothesen, die es Gehörlosen ermöglichen, Zugang zu auditiver Information wieder zu erlangen. Allerdings ist das resultierende Signal stark verzerrt bzw. degradiert und eine erfolgreiche Adaptation oft unvollständig. Das Verständnis zugrundeliegender perzeptueller Lernprozesse ist somit von enormer klinischer Bedeutung. Perzeptuelles Lernen degradierter Sprache lässt sich mittels Noise-Vokodierung bei Hörgesunden simulieren. In Bildgebungsstudien konnte anhand funktioneller Magnetresonanztomographie gezeigt werden, dass perzeptuelles Lernen degradierter Sprache mit einer Aktivitätssteigerung im linken inferior frontal gyrus (IFG) und linken inferior parietal cortex (IPC) assoziiert war. Die vorliegende Studie untersucht den Einfluss von fazilitierender, nicht-invasiver Hirnstromstimulation (anodale transkranielle Gleichstromstimulation, tDCS) über dem linken IFG und linken IPC auf das perzeptuelle Lernen {\\itshape{Noise}}-vokodierter Sprache. Die Probanden trainierten die Diskrimination von Minimal- (\"Tisch\"- \"Fisch\") und identen (\"Tisch\"- \"Tisch\") Wortpaaren, während der erste Stimulus akustisch degradiert, der zweite in geschriebener Form präsentiert wurden. Vor und nach dem Training wurden die trainierten Stimuli und eine gleiche Anzahl untrainierter Stimuli präsentiert. Perzeptuelles Lernen wurde in unserer Studie als eine Verbesserung der Diskriminationsleistung untrainierter Wortpaare operationalisiert. Zudem wurde vor und nach dem Training ein Elektroenzephalogramm abgeleitet. Auf elektrophysiologischer Ebene wurde der Einfluss des Lernvorgangs und der tDCS auf die N400 untersucht, welche mit der Verarbeitung lexiko-semantischer Informationen assoziiert ist. Unsere Ergebnisse zeigen, dass eine anodale tDCS über dem linken IFG perzeptuelles Lernen stark degradierter Sprache fazilitierte, während bei einer Placebo- bzw. einer Stimulation über dem linken IPC kein perzeptuelles Lernen stattfand.

Information theoretical approaches to language state that the most efficient communication oc­curs when the amount of information transmitted is distributed as uniformly as possible over time. Previous research has shown that speakers tend to adhere to strategies for distributing information efficiently, using mechanisms at multiple linguistic levels. This study aims to in­vestigate whether articulation rate (AR) is used in continuous speech to achieve a more uniform distribution of information within sentences, quantified as surprisal estimated by the state­-of-­the-­art language model GPT-­2, and if this has an effect on the amplitude of the N400 brain response in listeners. In neurolinguistics, surprisal has been observed to be a good predictor of the N400, which is related to processing of semantics and meaning in general. The results showed a significant, though small, effect of surprisal on AR, indicating that AR may have some role in achieving more uniform distribution of information on the word level. In line with previous research, surprisal showed an effect on the N400 where higher surprisal led to larger amplitudes. Results regarding AR and distributional effects on the N400 were inconclusive, although some independent effects of AR were found that could be further explored in more controlled experimental settings. / Informationsteoretiska perspektiv på språk säger att den mest effektiva kommunikationen sker när information sänds ut så jämnt fördelat som möjligt över tid. Tidigare studier har visat att talare tenderar att följa vissa strategier för att distribuera information jämnt, vilket de gör på flera språkliga nivåer. Denna studie ämnar att undersöka om artikulationshastighet (eng. articulation rate (AR)) används i kontinuerligt tal för att uppnå en mer jämn distribution av information inom meningar, kvantifierat som informationsteoretisk surprisal med hjälp av språkmodellen GPT-­2, samt om detta ger effekt på hjärnresponsen N400:s amplitud hos lyssnare. Inom neurolingvistik har surprisal visats kunna predicera N400, som är kopplad till bearbetning av semantik och meningsfullhet generellt. Resultaten visade en signifikant, om än liten, effekt av surprisal på AR, en indikator på att AR kan ha en roll i att uppnå mer jämn distribution av information på ordnivå. I linje med tidigare forskning så hade surprisal en inverkan på N400, där högre surprisal gav större amplituder. Resultaten utifrån AR och distribution av information var inte entydiga, däremot observerades vissa självständiga effekter av AR på amplituden av N400 och dessa skulle kunna vidare undersökas i mer kontrollerade experiment.

Difficulties in speech production are often marked by disfluency; fillers, hesitations, prolongations, repetitions and repairs. In recent years a body of work has emerged that demonstrates that listeners are sensitive to disfluency, and that this affects their expectations for upcoming speech, as well as their attention to the speech stream. This thesis investigates the extent to which delay may be responsible for triggering these effects. The experiments reported in this thesis build on an Event Related Potential (ERP) paradigm developed by Corley et al., (2007), in which participants listened to sentences manipulated by both fluency and predictability. Corley et al. reported an attenuated N400 effect for words following disfluent ers, and interpreted this as indicating that the extent to which listeners made predictions was reduced following an er. In the current set of experiments, various noisy interruptions were added to Corley et al.,'s paradigm, time matched to the disfluent fillers. These manipulations allowed investigation of whether the same effects could be triggered by delay alone, in the absence of a cue indicating that the speaker was experiencing difficulty. The first experiment, which contrasted disfluent ers with artificial beeps, revealed a small but significant reduction in N400 effect amplitude for words affected by ers but not by beeps. The second experiment, in which ers were contrasted with speaker generated coughs, revealed no fluency effects on the N400 effect. A third experiment combined the designs of Experiments 1 and 2 to verify whether the difference between them could be characterised as a context effect; one potential explanation for the difference between the outcomes of Experiments 1 and 2 is that the interpretation of an er is affected by the surrounding stimuli. However, in Experiment 3, once again no effect of fluency on the magnitude of the N400 effect was found. Taken together, the results of these three studies lead to the question of whether er's attenuation effect on the N400 is robust. In a second part to each study, listeners took part in a surprise recognition memory test, comprising words which had been the critical words in the previous task intermixed with new words which had not appeared anywhere in the sentences previously heard. Participants were significantly more successful at recognising words which had been unpredictable in their contexts, and, importantly, for Experiments 1 and 2, were significantly more successful at recognising words which had featured in disfluent or interrupted sentences. There was no difference between the recognition rates of words which had been disfluent and those which were affected by a noisy interruption. Collard et al., (2008) demonstrated that disfluency could raise attention to the speech stream, and the finding that interrupted words are equally well remembered leads to the suggestion that any noisy interruption can raise attention. Overall, the finding of memory benefits in response to disfluency, in the absence of attenuated N400 effects leads to the suggestion that different elements of disfluencies may be responsible for triggering these effects. The studies in this thesis also extend previous work by being designed to yield enough trials in the memory test portion of each experiment to permit ERP analysis of the memory data. Whilst clear ERP memory effects remained elusive, important progress was made in that memory ERPs were generated from a disfluency paradigm, and this provided a testing ground on which to demonstrate the use of linear mixed-effects modelling as an alternative to ANOVA analysis for ERPs. Mixed-effects models allow the analysis of unbalanced datasets, such as those generated in many memory experiments. Additionally, we demonstrate the ability to include crossed random effects for subjects and items, and when this is applied to the ERPs from the listening section of Experiment 1, the effect of fluency on N400 amplitude is no longer significant. Taken together, the results from the studies reported in this thesis suggest that temporal delay or disruption in speech can trigger raised attention, but do not necessarily trigger changes in listeners' expectations.

In order to investigate the temporal characteristics of cognitive processing, we apply multivariate phase synchronization analysis to event-related potentials. The experimental design combines a semantic incongruity in a sentence context with a physical mismatch (color change). In the ERP average, these result in an N400 component and a P300-like positivity, respectively. The synchronization analysis shows an effect of global desynchronization in the theta band around 288ms after stimulus presentation for the semantic incongruity, while the physical mismatch elicits an increase of global synchronization in the alpha band around 204ms. Both of these effects clearly precede those in the ERP average. Moreover, the delay between synchronization effect and ERP component correlates with the complexity of the cognitive processes.

In this study, the effect of semantic information processing was investigated by the oddball paradigm, by presenting consecutive Turkish words or word-like non-words while EEG signals are recorded. In an oddball paradigm, a series of events are presented of which one class is rarer than the other. Subjects are asked to respond to the infrequent stimuli (e.g. press a button, or count the number). The event related potential (ERP) component P300 obtained from EEG is considered as the marker of this attention capturing paradigm. P300 is obtained consistently for both visual and verbal stimulus. On the other hand, the ERP component N400 is consistently associated with semantic processing in neurolinguistics. Additionally, Late Positive Component (LPC) is a marker for the top-down attention mechanism during word comprehension. Moreover, there are other components, called early ERPs, which occur between 100-200 ms after the stimulus onset. These components orthographically and phonologically reflect low-level features of words. The target words chosen for our study are strictly limited to belong to a neutral category and not consist of any emotional content, to rule out emotional interference in semantic processing. Based on the ERP components that were obtained from this study, the LPC potential exhibited for words had higher amplitude than that of non-words consistently and statistically significantly. However, our study was confounded with the heterogeneity of non-words because some of the non-words were non-sense letter sequences while others were pseudowords. Due to this, although we observed the P300 and N400 ERPs consistently for all stimuli, we did not find significant differences for these potentials between words and non-words. To the best of our knowledge, our investigation is one of the few studies conducted with EEG recordings in a task that involved lexical decision making in Turkish.

Language is an essential component of human behavior. It is ubiquitous, but more importantly, it is malleable and it is constantly changing. Part of the dynamic nature of informal communication is the introduction and adoption of new linguistic elements. Online communication provides a window into this informal public discourse; therefore, it may be useful for testing hypotheses about the processes underlying the acquisition and use of new words. The comprehension of informal language may lead to an understanding of how these new informal words are integrated into our mental lexicon. The current study was an electroencephalographic (EEG) investigation of the brain processes that underlie informal language. We recorded event-related potentials while participants engaged in a lexical decision task. For this experiment, participants made judgments about Twitter targets primed with semantically related or unrelated words. Classic psycholinguistic studies have shown very specific event-related potentials (ERPs) for semantic processing. Most notably, the N400 event-related potential component is an index of lexical expectancy and semantic relatedness. In contrast to the literature, we did not find classic N400 priming effects. However, our results revealed marked differences between informal and traditional targets. Our results suggest that informal language is more difficult to process than traditional language.