Goal-directed actions frequently require a balance between antagonistic processes (e.g., executing and inhibiting a response), often showing an interdependency concerning what constitutes goal-directed behavior. While an inter-dependency of antagonistic actions is well described at a behavioral level, a possible inter-dependency of underlying processes at a neuronal level is still enigmatic. However, if there is an interdependency, it should be possible to predict the neurophysiological processes underlying inhibitory control based on the neural processes underlying speeded automatic responses. Based on that rationale, we applied artificial intelligence and source localization methods to human EEG recordings from N = 255 participants undergoing a response inhibition experiment (Go/Nogo task). We show that the amplitude and timing of scalp potentials and their functional neuroanatomical sources during inhibitory control can be inferred by conditional generative adversarial networks (cGANs) using neurophysiological data recorded during response execution. We provide insights into possible limitations in the use of cGANs to delineate the interdependency of antagonistic actions on a neurophysiological level. Nevertheless, artificial intelligence methods can provide information about interdependencies between opposing cognitive processes on a neurophysiological level with relevance for cognitive theory.

Executive functions, like the capacity to control and organize thoughts and behavior, develop from childhood to young adulthood. Although task switching and working memory processes are known to undergo strong developmental changes from childhood to adulthood, it is currently unknown how task switching processes are modulated between childhood and adulthood given that working memory processes are central to task switching. The aim of the current study is therefore to examine this question using a combined cue- and memory-based task switching paradigm in children (N = 25) and young adults (N = 25) in combination with neurophysiological (EEG) methods. We obtained an unexpected paradoxical effect suggesting that memory-based task switching is better in late childhood than in young adulthood. No group differences were observed in cue-based task switching. The neurophysiological data suggest that this effect is not due to altered attentional selection (P1, N1) or processes related to the updating, organization, and implementation of the new task-set (P3). Instead, alterations were found in the resolution of task-set conflict and the selection of an appropriate response (N2) when a task has to be switched. Our observation contrasts findings showing that cognitive control mechanisms reach their optimal functioning in early adulthood.

Longitudinal developmental fMRI studies just recently began to focus on within-subject reliability using the intraclass coefficient (ICC). It remains largely unclear which degree of reliability can be achieved in developmental studies and whether this depends on the type of task used. Therefore, we aimed to systematically investigate the reliability of three well-classified tasks: an emotional attention, a cognitive control, and an intertemporal choice paradigm. We hypothesized to find higher reliability in the cognitive task than in the emotional or reward-related task. 104 healthy mid-adolescents were scanned at age 14 and again at age 16 within M = 1.8 years using the same paradigms, scanner, and scanning protocols. Overall, we found both variability and stability (i.e. poor to excellent ICCs) depending largely on the region of interest (ROI) and task. Contrary to our hypothesis, whole brain reliability was fair for the cognitive control task but good for the emotional attention and intertemporal choice task. Subcortical ROIs (ventral striatum, amygdala) resulted in lower ICCs than visual ROIs. Current results add to the yet sparse overall ICC literature in both developing samples and adults. This study shows that analyses of stability, i.e. reliability, are helpful benchmarks for longitudinal studies and their implications for adolescent development.

Longitudinal developmental fMRI studies just recently began to focus on within-subject reliability using the intraclass coefficient (ICC). It remains largely unclear which degree of reliability can be achieved in developmental studies and whether this depends on the type of task used. Therefore, we aimed to systematically investigate the reliability of three well-classified tasks: an emotional attention, a cognitive control, and an intertemporal choice paradigm. We hypothesized to find higher reliability in the cognitive task than in the emotional or reward-related task. 104 healthy mid-adolescents were scanned at age 14 and again at age 16 within M = 1.8 years using the same paradigms, scanner, and scanning protocols. Overall, we found both variability and stability (i.e. poor to excellent ICCs) depending largely on the region of interest (ROI) and task. Contrary to our hypothesis, whole brain reliability was fair for the cognitive control task but good for the emotional attention and intertemporal choice task. Subcortical ROIs (ventral striatum, amygdala) resulted in lower ICCs than visual ROIs. Current results add to the yet sparse overall ICC literature in both developing samples and adults. This study shows that analyses of stability, i.e. reliability, are helpful benchmarks for longitudinal studies and their implications for adolescent development.

The neurophysiological processes underlying the inhibition of impulsive responses have been studied extensively. While also the role of theta oscillations during response inhibition is well examined, the relevance of resting-state theta activity for inhibitory control processes is largely unknown. We test the hypothesis that there are specific relationships between resting-state theta activity and sensory/motor coding levels during response inhibition using EEG methods. We show that resting theta activity is specifically linked to the stimulus-related fraction of neurophysiological activity in specific time windows during motor inhibition. In contrast, concomitantly coded processes related to decision-making or response selection as well as the behavioral inhibition performance were not associated with resting theta activity. Even at the peak of task-related theta power, where task-related theta activity and resting theta activity differed the most, there was still predominantly a significant correlation between both types of theta activity. This suggests that aspects similar to resting dynamics are evident in the proportion of inhibition-related neurophysiological activity that reflects an “alarm” signal, whose function is to process and indicate the need for cognitive control. Thus, specific aspects of task-related theta power may build upon resting theta activity when cognitive control is necessary.

Executive functions, like the capacity to control and organize thoughts and behavior, develop from childhood to young adulthood. Although task switching and working memory processes are known to undergo strong developmental changes from childhood to adulthood, it is currently unknown how task switching processes are modulated between childhood and adulthood given that working memory processes are central to task switching. The aim of the current study is therefore to examine this question using a combined cue- and memory-based task switching paradigm in children (N = 25) and young adults (N = 25) in combination with neurophysiological (EEG) methods. We obtained an unexpected paradoxical effect suggesting that memory-based task switching is better in late childhood than in young adulthood. No group differences were observed in cue-based task switching. The neurophysiological data suggest that this effect is not due to altered attentional selection (P1, N1) or processes related to the updating, organization, and implementation of the new task-set (P3). Instead, alterations were found in the resolution of task-set conflict and the selection of an appropriate response (N2) when a task has to be switched. Our observation contrasts findings showing that cognitive control mechanisms reach their optimal functioning in early adulthood.

Das Wortlernen begleitet unser Leben von der Kindheit bis ins Alter. Kleinkinder lernen ihre Muttersprache(n), aber auch Erwachsene lernen neue Wörter, z.B. beim Fremdspracherwerb. Unter gewissen Umständen muss eine neue Sprache wieder erlernen werden, wie z.B. nach einer Gehirnläsion. Wie meistert unser Gehirn diese herausfordernden Wortlernsituationen? Um die Neuroplastizität des Wortlernens zu untersuchen, wurden unterschiedliche neurowissenschaftliche Methoden (Elektroenzephalographie, funktionelle Nahinfrarotspektroskopie, voxel-basierte Läsion-Verhalten/EEG Mapping), teilweise in Kombination, bei Kleinkindern, Kindern und Erwachsenen sowie Patienten mit einer Gehirnläsion im Vergleich zu älteren Kontrollprobanden angewendet. 5 Experimente untersuchten die neuronale Verarbeitung von Pseudowörtern, welche mutter- und fremdsprachlichen phonotaktischen Regeln (d.h. die Kombination von verschiedenen Phonemen) folgten, in unterschiedlichen Lernsettings bei monolingualen Teilnehmern. Gesunde Erwachsene aber auch 6monatige und ältere Teilnehmer und Patienten konnten diese Regeln differenzieren. Beteiligte Gehirnareale umfassten ein links-hemisphärisches fronto-temporales Netzwerk. Die Verarbeitung universeller Spracheigenschaften, andererseits, zeigte sich in parietalen Regionen. Während Erwachsene eine klare Dominanz der linken Hemisphäre aufwiesen, nutzten 6monatige noch beide Gehirnhälften. Unterschiedliche Sprachtrainings (semantische Trainings oder Passives Zuhören) an drei aufeinanderfolgenden Tagen veränderten auch die Gehirnaktivität der Kleinkinder und der Erwachsenen und wiesen auf eine erhöhte Lernflexibilität hin. Im 6. Experiment lernten 5jährige bilinguale Kinder anhand pragmatischer Eigenschaften neue Adjektive und zeigten effizientere neuronale Mechanismen als Monolinguale. Die Ergebnisse unterstreichen die Wichtigkeit multi-methodologischer Ansätze, um genauere Einblicke in die komplexen Mechanismen der Neuroplastizität zu erlangen. / Word learning accompanies our everyday life from infancy to advanced age. Infants have to learn the native language(s) but also during adulthood word learning can take place, for example if we learn a new foreign language. Sometimes people are confronted with a situation in which they have to re-learn a language because of a brain lesion. How does the brain master these challenging word learning settings? To assess neuroplasticity of word learning several neuroscientific methods (electroencephalography, functional near-infrared spectroscopy, voxel-based lesion-behavior/EEG mapping), partially in combination, were used in infants, children, and adults as well as in patients suffering from a brain lesion compared to matched elderly controls. In 5 experiments neuronal processing of pseudowords corresponding to native and non-native phonotactic rules (i.e., the combination of different phonemes) was investigated under different learning conditions in monolingual participants. Healthy adults but also 6-month-old infants and elderly subjects and patients were able to differentiate these rules. Involved brain areas included a left-hemispheric network of fronto-temporal regions. When processing universal linguistic features, however, more parietal regions were involved. While adults revealed a clear left-dominant network, 6-month-olds still recruited bilateral brain areas. Differential language trainings (semantic or passive listening trainings) over three consecutive days also modulated brain activation in both infants and adults suggesting a high flexibility for learning native and non-native linguistic regularities. In a 6th experiment, bilingual 5-year-old children learned novel adjectives by means of pragmatic cues and revealed more efficient neuronal mechanisms compared to monolingual children. Findings underline the importance of multi-methodological approaches to get clearer insights into the complex machinery of neuroplasticity.

Menschliche Hirnsignale von der Kopfhaut bieten einen Einblick in die neuronalen Prozesse, denen Wahrnehmung, Denken und Verhalten zugrunde liegen. Rhythmen, die historisch den Grundstein für die Erforschung großflächiger Hirnsignale legten, sind ein häufiges Zeichen neuronaler Koordination, und damit von weitem Interesse für die kognitiven, systemischen und komputationalen Neurowissenschaften. Typischen Messungen von Rhythmizität fehlt es jedoch an Details, z. B. wann und wie lange Rhythmen auftreten. Darüber hinaus weisen neuronale Zeitreihen zahlreiche dynamische Muster auf, von denen nur einige rhythmisch erscheinen. Obwohl aperiodischen Beiträgen traditionell der Status irrelevanten „Rauschens“ zugeschrieben wird, attestieren neuere Erkenntnisse ihnen ebenfalls eine Signalrolle in Bezug auf latente Hirndynamik. Diese kumulative Dissertation fasst Projekte zusammen, die darauf abzielen, rhythmische und aperiodische Beiträge zum menschlichen Elektroenzephalogramm (EEG) methodisch zu dissoziieren, und ihre Relevanz für die flexible Wahrnehmung zu untersuchen. Projekt 1 ermittelt insbesondere die Notwendigkeit und Durchführbarkeit der Trennung rhythmischer von aperiodischer Aktivität in kontinuierlichen Signalen. Projekt 2 kehrt diese Perspektive um und prüft Multiscale Entropy als Index für die Unregelmäßigkeit von Zeitreihen. Diese Arbeit weist auf methodische Probleme in der klassischen Messung zeitlicher Unregelmäßigkeit hin, und schlägt Lösungen für zukünftige Anwendungen vor. Abschließend untersucht Projekt 3 die neurokognitive Relevanz rhythmischer und aperiodischer Zustände. Anhand eines parallelen multimodalen EEG-fMRT-Designs mit gleichzeitiger Pupillenmessung liefert dieses Projekt erste Hinweise dafür, dass erhöhte kognitive Anforderungen Hirnsignale von einem rhythmischen zu einem unregelmäßigen Regime verschieben und impliziert gleichzeitige Neuromodulation und thalamische Aktivierung in diesem Regimewechsel. / Non-invasive signals recorded from the human scalp provide a window on the neural dynamics that shape perception, cognition and action. Historically motivating the assessment of large-scale network dynamics, rhythms are a ubiquitous sign of neural coordination, and a major signal of interest in the cognitive, systems, and computational neurosciences. However, typical descriptions of rhythmicity lack detail, e.g., failing to indicate when and for how long rhythms occur. Moreover, neural times series exhibit a wealth of dynamic patterns, only some of which appear rhythmic. While aperiodic contributions are traditionally relegated to the status of irrelevant ‘noise’, they may be informative of latent processing regimes in their own right. This cumulative dissertation summarizes and discusses work that (a) aims to methodologically dissociate rhythmic and aperiodic contributions to human electroencephalogram (EEG) signals, and (b) probes their relevance for flexible cognition. Specifically, Project 1 highlights the necessity, feasibility and limitations of dissociating rhythmic from aperiodic activity at the single-trial level. Project 2 inverts this perspective, and examines the utility of multi-scale entropy as an index for the irregularity of brain dynamics, with a focus on the relation to rhythmic and aperiodic descriptions. By highlighting prior biases and proposing solutions, this work indicates future directions for measurements of temporal irregularity. Finally, Project 3 examines the neurocognitive relevance of rhythmic and aperiodic regimes with regard to the neurophysiological context in which they may be engaged. Using a parallel multi-modal EEG-fMRI design with concurrent pupillometry, this project provides initial evidence that elevated demands shift cortical dynamics from a rhythmic to an irregular regime; and implicates concurrent phasic neuromodulation and subcortical thalamic engagement in these regime shifts.