Bei altersbedingt abnehmender kognitiver Funktion stellt das steigende Renteneintrittsalter Arbeitgeber und -nehmer vor wachsende Herausforderungen. Der Aufbau der kognitiven Reserve (CR) durch geistig stimulierende Aktivitäten verspricht eine Resilienz gegenüber neuropathologisch bedingten kognitiven Defiziten. In der vorliegenden Arbeit wird die Rolle der CR in Bezug auf die kognitive Leistungsfähigkeit und die neuronale Informationsverarbeitung gesunder Erwachsener im Berufsalter untersucht. Unter Ableitung des Elektroenzephalogramms bearbeiteten Probanden mittleren und hohen Erwerbsalters (34-45 J. und 46-62 J.) im 2-Jahres-Abstand Aufgaben zu drei Domänen exekutiver Funktionen: Arbeitsgedächtnis (AG), kognitive Flexibilität und Inhibitionskontrolle. Hoch-CR-Probanden wiesen aufgabenübergreifend schnellere Reaktionen und geringere Fehlerraten auf. Reduzierte Leistung ließ sich in der Gering-CR-Gruppe tendenziell bei älteren Probanden und in anspruchsvollen Aufgabenbedingungen beobachten. Nach 2 Jahren zeigten Gering-CR-Ältere eine numerisch abnehmende AG-Kapazität, während Hoch-CR-Ältere ihre hohe Leistung steigern konnten. Die P3-Amplitude variierte in Abhängigkeit von der CR und dem Alter. Hoch-CR-Jüngere wiesen im Vergleich zu Gering-CR-Jüngeren höhere P3-Amplituden auf, während Hoch-CR-Ältere im Gegensatz zu Gering-CR-Älteren kleinere P3-Amplituden generierten. Zudem legten kürzere P3-Latenzen in der Hoch-CR-Gruppe eine schnellere neuronale Verarbeitungsgeschwindigkeit nahe. In der Aufgabe zur kognitiven Flexibilität ließ sich bei Gering-CR-Probanden ein Anterior-Shift der P3 beobachten. Die Untersuchungsergebnisse konnten nach 2 Jahren repliziert werden. Alterungsrelevante Leistungsvariablen und neuronale Informationsverarbeitungsprozesse zeigten sich bereits im Berufsalter sensitiv gegenüber der CR. Das mittlere Erwachsenenalter sollte bei der Erarbeitung und Evaluation CR-basierter Maßnahmen zur Prävention kognitiver Defizite stärker berücksichtigt werden. / The increasing retirement date accompanied by an age-associated decline of cognitive functions poses growing challenges to employers and employees. The cognitive reserve (CR) promises a resilience to brain damage-associated cognitive deficits through intellectually stimulating lifestyle activities. The present study examines the role of CR relating to cognitive performance and neuronal information processing of healthy adults in working age. Using an electroencephalogram, subjects of middle and high working age (34-45 years and 46-62 years of age, respectively) completed tasks on three domains of executive functions: working memory, cognitive flexibility and inhibition control. Follow-up assessments were conducted after two years. High-CR subjects performed better across tasks than Low-CR subjects, with faster reaction times and lower error rates. Reduced performance in the Low-CR group tended to be more common among older participants and during the more challenging task conditions. In addition, after two years, Low-CR older workers showed a decreased working memory capacity while older High-CR individuals improved their higher performance. The P3 amplitude of the event-related brain potential varied systematically as a function of CR and age. High-CR younger individuals revealed higher P3 amplitudes compared to Low-CR younger individuals, while High-CR older individuals generated smaller P3 amplitudes than Low-CR older individuals. The shorter P3 peak-latencies of the High-CR group suggested moreover a difference in neural processing speed. When testing cognitive flexibility an anterior shift of the P3 was observed in older Low-CR subjects. The results were almost completely replicated after two years. Age-related performance variables and neuronal information processes revealed to be sensitive to CR already at working age. These findings recommend more research on early adulthood in the development and evaluation of CR-based programs to prevent cognitive deficits.

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.

<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>

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).

<p> Hearing provides a vital means for infants to discover their environment and communicate with their caregivers. Identifying and discriminating the pitch of sounds is critical for infants in order to acquire information from speech and music. Therefore, how infants process pitch is a fundamental question in research on auditory development. The focus of this dissertation is the use of auditory event related potentials (ERPs) derived from electroencephalogram (EEG) recordings to examine the maturation of pitch perception in early infancy. </p> <p> Pitch perception in adults has been extensively studied, but little is known about the development of pitch perception during early infancy. Infant mismatch responses (MMRs) are ERP components that are elicited by infrequent changes in auditory stimuli. MMR is a promising tool to study infant pitch perception because it can be elicited without attention or a behavioural response. However, previous studies on MMRs in infants have reported inconsistent results, some reporting frontally positive responses while others report frontally negative mismatch responses. In Chapter 2, we examined MMRs to simple pitch changes in infants between 2 and 4 months of age and found both types of infant MMRs are present, but the morphological distributions and developmental trajectories are different. In Chapter 3, we reported that both types of infant MMRs are affected similarly by the amplitude of pitch change but only the positive MMR becomes stronger when stimulus presentation rate increases, which suggests different neural mechanisms for the two types of infant MMRs. The studies reported in Chapter 4 found that only the negative MMR can be elicited readily by changes in pitch patterns, suggesting that it may be functionally similar to mismatch negativity (MMN) in adults. </p> <p> The experiments in Chapter 5 used MMR as the indication of whether infants automatically integrate the frequency components of a complex tone into a single pitch percept, even when the fundamental frequency component (corresponding to the pitch) is removed. Previous studies show that adult MMN is elicited by a pitch change in such tones missing the fundamental. Previous behavioural studies using a conditioned head tum method show that 7-month-olds also perceive pitch with tones missing the fundamental. The results of the present study indicate that infants as young as 4 months of age integrate components into a single pitch percept, but evidence for this in younger infants could not be found. </p> <p> In conclusion, the current dissertation established a promising procedure utilizing infant MMR to study infant pitch perception and contributed to the knowledge of early development of pitch perception by demonstrating dramatic changes in brain response to pitch in harmonic tones in infants between 2 and 4 months old, and to pitch in tones in infants missing the fundamental between 3 and 4 months old . </p> / Thesis / Doctor of Philosophy (PhD)

Die Reaktionsauswahl und die visuelle Aufmerksamkeit sind kapazitätslimitiert. In Doppelaufgaben des Paradigmas der Psychologischen Refraktärperiode (PRP) wird angenommen, dass die Reaktionsauswahlstufen in Aufgabe 1 und Aufgabe 2 sequentiell verarbeitet werden. Für Konjunktionssuchaufgaben wird angenommen, dass die visuelle Aufmerksamkeit Objekte selektiert und Objektmerkmale zusammen bindet, was zu einem seriellen Suchprozess führt. In der vorliegenden Dissertation wurde untersucht, ob die visuelle Aufmerksamkeit (d.h. Merkmalsbindung) demselben zentralen Verarbeitungsengpass wie die Reaktionsauswahl in Doppelaufgaben unterliegt. Sequentielle Verarbeitung von Reaktionsauswahl und visueller Aufmerksamkeit würde Evidenz dafür zeigen, dass beide Prozesse derselben Kapazitätslimitation unterliegen, während parallele Verarbeitung Evidenz dafür zeigen würde, dass beide Prozesse unterschiedlichen Kapazitätslimitationen unterliegen. Um diese Frage zu untersuchen, wurden Reaktionszeitmaße (locus-of-slack Methode), Targetdetektionsmaße (d’) und Ereigniskorrelierte Potentiale (EKPs; N2pc (N2 posterior contralateral)) gemessen. Schwerpunkt aller Analysen war der visuelle Aufmerksamkeitsprozess in einer Konjunktionssuche, die als Aufgabe 2 in Doppelaufgaben implementiert wurde. Aufgabe 1 war stets eine Wahlunterscheidungsaufgabe. Die Verhaltens- und elektrophysiologischen Ergebnisse zeigten, dass die Reaktionsauswahl in Aufgabe 1 und die visuelle Aufmerksamkeit (d.h. Merkmalsbindung) in Aufgabe 2 parallel verarbeitet wurden unabhängig von der Stimulusmodalität in Aufgabe 1, der Schwierigkeit der Reaktionsauswahl in Aufgabe 1 und der Darbietungsform des Stimulusdisplays in Aufgabe 2. Außerdem wurde eine Methode entwickelt, um die Anzahl der Objekte zu berechnen, die parallel zur Reaktionsauswahl verarbeitet wurden. Die Berechnungen stützten die Konklusion, dass die Reaktionsauswahl und die visuelle Aufmerksamkeit unterschiedlichen Kapazitätslimitationen unterliegen. / Response selection and visual attention are limited in capacity. Concerning dual-tasks of the Psychological Refractory Period (PRP) paradigm, it is assumed that response selection of Task 1 and Task 2 are processed sequentially. On the other hand, concerning conjunction search, it is assumed that visual attention selects the items and binds the item features resulting in a serial search process. In the present dissertation I investigated whether visual attention (i.e., feature binding) is subject to the same bottleneck mechanism as response selection in dual-tasks. Sequential processing of response selection and visual attention would provide evidence that both processes rely on a common capacity limitation, whereas concurrent processing would provide evidence that they rely on distinct capacity limitations. Reaction time (RT) measures based on the locus-of-slack method, target detectability measures based on d’, and the event-related potential (ERP) technique to measure the N2pc (N2 posterior contralateral) were combined to investigate this question. Analyses focused on visual attention deployment in a conjunction search task, which was implemented as Task 2 in dual-task situations. Task 1 was a choice discrimination task. Both tasks were presented at variable temporal overlap (Stimulus Onset Asynchrony, SOA). The behavioral and N2pc results showed that response selection in Task 1 and visual attention (i.e., feature binding) in Task 2 operated concurrently irrespective of the stimulus modality in Task 1, the response selection difficulty in Task 1 and the type of presentation of the search display in Task 2. Based on a method that was developed in the present dissertation, it was possible to calculate how many items of the search display were processed in parallel to response selection. The results supported the conclusion that response selection and visual attention rely on distinct capacity limitations.

Informelle Berichte zeigten größere Amplituden der durch Gesichter ausgelösten N170 Komponente im Ereigniskorrelierten Potenzial (EKP) bei asiatischen als bei kaukasischen Probanden. Als mögliche Ursache vermutete ich unterschiedliche Erfahrungen mit logographischen bzw. alphabetischen Schriftsystemen (Schriftsystem-Hypothese) oder die verstärkte Exposition mit unbekannten Gesichtern während der Immersion in eine neue soziale oder ethnische Umgebung (soziale Immersions-Hypothese). Zur Überprüfung dieser Hypothesen führte ich zwei kulturvergleichende Studien mit Erwachsenen bzw. Kindern durch. In Studie 1 untersuchte ich einheimische Chinesen und nicht-chinesische Auswärtige in Hongkong und deutsche Einheimische und chinesische Auswärtige in Berlin. Die Auswärtigen an beiden Orten zeigten größere N170 Amplituden auf Gesichter als die Einheimischen. Außerdem zeigten Deutsche, die erst kurze Zeit in Berlin lebten ähnliche Amplituden wie langjährige Einheimische. Insgesamt unterstützt Studie 1 die soziale Immersions-Hypothese, dass die Immersion in eine neue ethnische Umgebung zu einer Vergrößerung der N170 führt. Studie 2 untersuchte die Schriftsystem-Hypothese bei chinesischen und deutschen Erstlesern am Ende der ersten oder zu Beginn des zweiten Schuljahres an ihrem jeweiligen Heimatort. Die Ergebnisse unterstützen die Schriftsystem-Hypothese, dass chinesische Kinder eine größere N170 auf Gesichter zeigen als deutsche. Insgesamt konnte die vorliegende Dissertation zwei neue Einfluss-Faktoren auf das Gesichterverarbeitungs-System nachweisen, das erworbene Schriftsystem (logographische versus alphabetisch) und die Erfahrung sozialer Immersion in eine neue ethnische Umgebung. Diese Effekte zu ganz unterschiedlichen Zeitpunkten der Entwicklung (Kindheit vs. junges Erwachsenen-Alter) zeigen, dass das Gesichterverarbeitungs-System über lange Zeit seine Plastizität behält. / Informal reports have shown larger face-elicited N170 component of event-related potential (ERP) in Asians than Caucasians participants. I proposed that different experience with logographic versus alphabetic scripts (script system hypothesis) or by exposure to abundant novel faces during the immersion into a new social and/or ethnic environment (social immersion hypothesis) as a possible cause. To test these hypotheses, I conducted two cross-cultural ERP studies with adults and Children. In Study 1, I examined Chinese locals and non-Chinese foreigners in Hongkong, and German locals and Chinese foreigners in Berlin. It turned out that the foreigners in both locations showed larger N170 amplitudes to faces than the locals. In addition, Germans who had only lived in Berlin for a short time showed similar face N170 amplitudes as long-term Berlin residents. In sum, Study 1 supports the social immersion hypothesis that immersing into a new ethnic environment drives an increase of face N170. Study 2 investigated the scripts system hypothesis in Chinese and German early readers assessed at the end of the first-grade or at the beginning of the second grade in their respective home towns. The findings support the script system hypothesis that Chinese children showed larger face N170 amplitudes than German children. Overall, the present thesis demonstrated two new influencing factors on the face processing system, the acquired script system (logographic vs. alphabetic) and the social immersion experience in a new ethnic environment. More specifically, learning to read a visually complex logographic Chinese script or immersing into an other-ethnic social environment facilitates early perceptual processing of faces. These effects acquired at different stages of development (early childhood versus young adulthood) show that the face processing system retains its plasticity over a long period of time.