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- Kognition (5) (entfernen)
The distractor-response binding effect (Frings & Rothermund, 2011; Frings, Rothermund, & Wentura, 2007; Rothermund, Wentura, & De Houwer, 2005) is based on the idea that irrelevant information will be integrated with the response to the relevant stimuli in an episodic memory trace. The immediate re-encounter of any aspect of this saved episode " be it relevant or irrelevant " can lead to retrieval of the whole episode. As a consequence, the previously executed and now retrieved response may influencing the response to the current relevant stimulus. That is, the current response may either be facilitated or be impaired by the retrieved response, depending on whether it is compatible or incompatible to the currently demanded response. Previous research on this kind of episodic retrieval focused on the influence on action control. I examined if distractor response binding also plays a role in decision making in addition to action control. To this end I adapted the distractor-to-distractor priming paradigm (Frings et al., 2007) and conducted nine experiments in which participants had to decide as fast as possible which disease a fictional patient suffered from. To infer the correct diagnosis, two cues were presented; one did not give any hint for a disease (the irrelevant cue), whereas the other did (the relevant cue). Experiments 1a to 1c showed that the distractor-response binding effect is present in deterministic decision situations. Further, experiments 2a and 2b indicate that distractor-response binding also influences decisions under uncertainty. Finally, experiments 3a to 3d were conducted to test some constraints and underlying mechanisms of the distractor-response binding effect in decision making under uncertainty. In sum, these nine experiments provide strong evidence that distractor-response binding influences decision making.
Fast and Slow Effects of Cortisol on Several Functions of the Central Nervous System in Humans
(2014)
Cortisol is one of the key substances released during stress to restore homeostasis. Our knowledge of the impact of this glucocorticoid on cognition and behavior in humans is, however, still limited. Two modes of action of cortisol are known, a rapid, nongenomic and a slow, genomic mode. Both mechanisms appear to be involved in mediating the various effects of stress on cognition. Here, three experiments are presented that investigated fast and slow effects of cortisol on several functions of the human brain. The first experiment investigated the interaction between insulin and slow, genomic cortisol effects on resting regional cerebral blood flow (rCBF) in 48 young men. A bilateral, locally distinct increase in rCBF in the insular cortex was observed 37 to 58 minutes after intranasal insulin admission. Cortisol did not influence rCBF, neither alone nor in interaction with insulin. This finding suggests that cortisol does not influence resting cerebral blood flow within a genomic timeframe. The second experiment examined fast cortisol effects on memory retrieval. 40 participants (20 of them female) learned associations between neutral male faces and social descriptions and were tested for recall one week later. Cortisol administered intravenously 8 minutes before retrieval influenced recall performance in an inverted U-shaped dose-response relationship. This study demonstrates a rapid, presumably nongenomic cortisol effect on memory retrieval in humans. The third experiment studied rapid cortisol effects on early multisensory integration. 24 male participants were tested twice in a focused cross-modal choice reaction time paradigm, once after cortisol and once after placebo infusion. Cortisol acutely enhanced the integration of visual targets and startling auditory distractors, when both stimuli appeared in the same sensory hemi-field. The rapidity of effect onset strongly suggests that cortisol changes multisensory integration by a nongenomic mechanism. The work presented in this thesis highlights the essential role of cortisol as a fast acting agent during the stress response. Both the second and the third experiment provide new evidence of nongenomic cortisol effects on human cognition and behavior. Future studies should continue to investigate the impact of rapid cortisol effects on the functioning of the human brain.
By rodent studies it has been shown that the mineralocorticoid receptor (MR) is a candidate gene for the investigation of cognitive functions comparable to human executive function. The present work addresses the question if polymorphisms in the MR gene can act as a "probe" to explain a part of the interindividual variance of human executive functions. For this purpose, 72 healthy young participants were assigned to four equally sized groups, concerning their particular MR genotype for two common MR polymorphisms. They were investigated in an electroencephalogram (EEG) test session, accomplishing two cognitive tests while delivering saliva samples for subsequent cortisol measures. The two tests chosen for the assessment of executive functions were the Attention Network Task (ANT) and a modified version of the Wisconsin Card Sorting Test (WCST).Chapter 1 of the present work reports of the rational bases for the empirical approach, which were built up on a broad theoretical background presented in Chapter 2. In the third chapter, the investigation and results of the statistical analysis for behavioral data (i.e. reaction times, accuracy/error rates) are presented. No association with MR polymorphisms was found for the reaction times of both tests. For the accuracy rate, differences between genotype groups were found for ANT and WCST, indicating an association of MR polymorphisms and accuracy in the Alertness and Executive Control network of the ANT and during the detection of an intradimensional shift in the WCST. Data acquisition and the results for EEG data analyses are presented in Chapter 4. The results show that groups differing for MR genotype show different activity over prefrontal motor areas during the process of answering to the ANT. Those group differences again were prominent for the Alertness and Executive Control network. A tendency for further significant group differences was found for activity on frontopolar positions in extradimensional rule switching. Chapter 5 summarizes the findings for the analysis of salivary free cortisol, showing a tendency for an association between MR polymorphisms and a mildly stimulated Hypothalamus-pituitary-adrenal (HPA) axis during the test situation. The results of the different measures are integrated and discussed in Chapter 6 within the scope of novel findings in investigating the functionality of the chosen MR polymorphisms. Finally, Chapter 7 gives an outlook on the methodology and constraints of future research strategies to further describe the role of the MR in human cognitive function.
This thesis presents a study of the visual change detection mechanism. This mechanism is thought to be responsible for the detection of sudden and unexpected changes in our visual environment. As the brain is a capacity limited system and has to deal with a continuous stream of information from its surroundings only a part of the vast amount of information can be completely processed and be brought to conscious awareness. This information, which passes through attentional filters, is used for goal-directed behaviour. Therefore, the change detection mechanism is a very useful aid to cope with important information which is outside the focus of our attention. rnIt is thought that a neural memory trace of repetitive visual information is stored. Each new information input is compared to this existing memory trace by a so-called change or mismatch detection system. Following a sudden change, the comparison process leads to a mismatch and the detection system elicits a warning signal, to which an orienting response can follow. This involves a change in the focus of attention towards this sudden environmental change which can then be evaluated for potential danger and allows for a behavioural adaptation to the new situation. rnTo this purpose a paradigm was developed combining a 2-choice response time task with in the background a mismatch detection task of which the subjects were not aware. This paradigm was implemented in an ERP and an fMRI study and was used to study the the change detection mechanism and its relationship with impulsivity.rnIn previous studies a change detection system for auditory information had already been established. As the brain is a very efficient system it was thought to be unlikely that this change detection system is only available for the processing of auditory information. rnIndeed, a modality specific mismatch response at the sensory specific occipital cortex and a more general response at the frontocentral midline, both resembling the components shown in auditory research, were found in the ERP study.rnAdditionally, magnetic resonance imaging revealed a possible functional network of regions, which responded specifically to the processing of a deviant. These regions included the occipital gyrus, premotor cortex, inferior frontal cortex, thalamas, insula, and parts of the cingular cortex. rnThe relationship between impulsivity measures and visual change detection was established in an additional study. More impulsive subjects showed less detection of deviant stimuli, which was most likely due to too fast and imprecise information processing.rnIn summary it can be said, that the work presented in this thesis demonstrates that visual mismatch negativity was established, a number of regions could be associated with change detection and additionally the relevance of change detection in information processing was shown.rn
Mit der Übernahme eines Ziels oder einer Aufgabe wird die Aufmerksamkeit auf ziel- bzw. aufgabenbezogene Informationen fokussiert. Bei dieser Fokussierung können zwei Komponenten unterschieden werden: (1) eine erhöhte kognitive Resonanz für relevante Informationen und (2) eine Blockierung der Verarbeitung irrelevanter Informationen. Die zielbezogene kognitive Fokussierung wird typischerweise wieder aufgehoben, wenn das Ziel erreicht bzw. die Aufgabe erfolgreich bearbeitet ist. Aber was geschieht mit der zielbezogenen Aufmerksamkeitseinstellung nach einem definitiven Scheitern der Zielverfolgung? In einer ersten Experimentalserie wurde die kognitive Resonanz für zielbezogene Information nach induziertem Mißerfolg untersucht. In der ersten Phase der Experimente erhielten die Untersuchungsteilnehmer positive oder negative Leistungsrückmeldung bei der Bearbeitung einer komplexen Labyrinthaufgabe (Experiment 1) bzw. mehrerer Synonymaufgaben (Experiment 2). In der zweiten Phase der Experimente wurden automatische Aufmerksamkeitsbindungen für Stimuli gemessen, die einen inhaltlichen Bezug zu den vorher bearbeiteten Labyrinth- bzw. Synonymaufgaben besitzen. Hierzu wurden die Stimuli als Distraktoren in einer Wort-Lese-Aufgabe dargeboten. In beiden Experimenten waren die Interferenzeffekte für die Distraktoren in der Mißerfolgsbedingung erhöht. In einer zweiten Experimentalserie wurde die Inhibition aufgabenirrelevanter Information nach Mißerfolg analysiert. In einer ersten Studie mußten die Teilnehmer ein lösbares oder unlösbares Labyrinth bearbeiten. Währenddessen wurden akustisch Distraktorwörter dargeboten (Experiment 3). Während der Bearbeitung der Labyrinthaufgabe wurde die Inhibition der irrelevanten Stimuli kontinuierlich erfaßt, indem die Distraktorwörter als Stimuli in einer simultan zu bearbeitenden Farbbenennaufgabe präsentiert wurden. Bei der unlösbaren Labyrinthaufgabe nahmen die Interferenzeffekte der Distraktoren während der Bearbeitung zu, nicht aber bei der Bearbeitung der lösbaren Aufgabe. In zwei weiteren Experimenten wurde untersucht, ob vormals ausgeblendete irrelevante Information nach einem Scheitern der Zielverfolgung disinhibiert wird (Experimente 4 und 5). Hierbei mußten die Teilnehmer eine Reihe von Konzeptidentifikationsaufgaben bearbeiten. Während der Aufgabenbearbeitung wurde die kognitive Zugänglichkeit der verschiedenen Objektmerkmale über Interferenzeffekte in einer zusätzlich zu bearbeitenden Farbbenennaufgabe gemessen. Die Zurückweisung eines Merkmals in der Konzeptidentifikationsaufgabe führte zu einer Inhibition des korrespondierenden Merkmalsbegriffs. Durch Einstreuen invalider Rückmeldungen konnte eine Situation hergestellt werden, in der alle möglichen Merkmale der Konzeptidentifikationsaufgabe widerlegt wurden. In dieser Situation war die globale Suchstrategie als Ganze gescheitert und die vorher inhibierten Merkmale wurden wieder zugänglich. Zusammengenommen stützen die Experimente die Hypothese, daß Mechanismen einer bevorzugten Verarbeitung relevanter Information und einer Ausblendung irrelevanter Information durch Mißerfolg unterschiedlich beeinflußt werden. Eine erhöhte kognitive Resonanz für zielbezogene Information persistiert auch nach einem definitiven Scheitern der Zielverfolgung. Diese Perseveranz der Sensitivität für zielbezogene Information garantiert, daß mögliche zukünftige Gelegenheiten für eine erfolgreiche Zielverfolgung nicht übersehen werden. Eine Inhibition irrelevanter Informationen wird angesichts eines Scheiterns der Zielverfolgung allerdings nicht aufrechterhalten. Die Erfahrung wiederholter erfolgloser Bemühungen der Zielerreichung induziert einen offenen, defokalisierten Modus der Informationsverarbeitung, der für eine Neuorientierung nach Mißerfolg funktional ist.