Herrmann, Manfred
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Herrmann, Manfred
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Herrmann, Manfred
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Item-typ:Veröffentlichung, Neurobiological Correlates of Pathological Gambling: Temporo-Spatial Evidence Derived from fMRI and EEG Studies(2009-12-02); ; ; In the first study functional magnetic resonance imaging (fMRI) data in occasional gamblers (OG) and pathological gamblers (PG) were obtained during a quasi-realistic blackjack game. The present experiment focused on neuronal correlates of risk assessment and reward processing. Participants had to decide whether to draw or not to draw a card in a high-risk or low-risk blackjack situation. It was assumed, that PG would show differences in prefrontal and ventral striatal brain regions in comparison to OG during risk assessment and as a consequence of winning or losing money. Although both groups did not differ with respect to behavioral data, blood oxygen level dependent (BOLD) signals in PG and OG significantly differed in thalamic, inferior frontal, and superior temporal regions. Whereas PG demonstrated a consistent signal increase during high-risk situations and a decrease in low-risk situations, OG presented the opposite pattern. During reward processing as derived from contrasting winning vs. losing situations, both PG and OG groups showed an enhancement of ventral striatal and posterior cingulate activity. Furthermore, PG demonstrated a distinct fronto-parietal activation pattern which has been discussed to reflect a cue-induced addiction memory network triggered by gambling-related cues. The second experiment investigated event-related potentials (ERPs) in occasional gamblers (OG) and pathological gamblers (PG) during a quasi-realistic blackjack scenario to examine regional source (RS) models of risk assessment and reward processing based on fMRI activation patterns from experiment 1. Participants had to decide whether (to draw) or not to draw a card in a high-risk or low-risk blackjack situation. Although both groups did not differ in behavioral data, ERP signals in PG and OG significantly differed in P3b and late positive potential (LPP) amplitudes on high-risk vs. low-risk decisions. An fMRI constrained RS model during risk assessment yielded larger source moments in PG in the high-risk vs. low-risk comparison during early time windows in frontal and temporal brain regions, followed by thalamic, frontal, and temporal activations within later time windows. During reward processing, as derived from contrasting winning vs. losing situations, PG demonstrated enhanced fronto-central N1 amplitude and centro-parietal differences in the P3b time window. There were larger source moments in PG during early time windows in fronto-central and parietal networks, followed by middle frontal source activity in the 400-450 ms (millisecond) time window. Pathological gambling (PGG) is suggested to be reflected by early risk-related frontal and temporal modulations, which became not significant in ERPs, followed by enhanced P3b amplitude, probably associated with intensified evaluation processing or context updating in high-risk decisions. LPP enhancement in high-risk decisions in PG might represent stronger cue-related craving or arousal, potentially triggered by thalamic, frontal, and temporal generators. Early N1 enhancement in PG during win trials might reflect early attentional processing, probably generated in anterior cingulate cortex. Later valence-related P3b modulations in PG point to increased context updating with underlying frontal sources. To conclude, high-risk as well as win situations might serve as cues in PG reflected in stronger activations in arousal-related brain networks.Dissertation312 202 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Multimodale Charakterisierung von Patienten mit Vertebralarteriendissektion, funktionelles Outcome und Lebensqualität sowie Korrelation zu psychischen, kognitiven und neurologischen Merkmalen - eine explorative Untersuchung(2016-11-17); ; ; Background and Purpose: Cervical artery dissections may cause cerebral ischemia and impair quality of life despite of good functional outcome. The aim of this study was the multimodal analysis of such patients. Methods: In a prospective exploratory study consecutive patients with vertebral artery dissection, patients with cerebral ischemia without dissection and stroke mimics were examined for psychological, cognitive and neurological factors, functional outcome and quality of life. Results: About 40% of patients with vertebral artery dissection showed reduced quality of life despite of good mid-term functional outcome. Subgroup analysis yielded significantly higher screening scores for posttraumatic stress symptoms predictive for quality of life. This finding could be interpreted as maladaptive psychological reaction. Conclusion: Posttraumatic stress symptoms are significantly important for the quality of life after vertebral artery dissection. The screening tools used in this study may enable the early detection of psychological, neurological and cognitive impairments, therapeutic interventions and a better quality of life.Dissertation406 835 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Emotions in Motion: Processing of Dynamic and Static Facial Expressions of Happiness and Disgust Investigated by FMRI and EEG(2008-11-05); ; ; The aim of the present dissertation was to reveal the spatio-temporal processing of dynamic and static facial expressions of happiness and disgust investigated by fMRI and EEG. The fMRI study resulted in stronger and more widespread activation patterns for the processing of happy and disgusted compared to neutral faces in, e.g., the amygdala, inferior frontal, occipital, superior temporal regions and the fusiform gyrus (FuG). The time course of static and dynamic emotional face processing was investigated with a high-resolution EEG using the same study design. ERP data of static facial expressions indicated a stronger deflection of the N170 in right-lateralized posterior electrode sites for emotional compared to neutral stimuli. Both, static and dynamic facial expressions showed a sustained positivity (LPP) over centro-parietal areas for emotional compared to neutral. Among other, a constrained regional source model of static stimuli revealed an emotional modulation of the insula with an enhancement of activity of disgust compared to neutral stimuli between 300 and 350 ms. Source power in dynamic stimuli yielded an enhancement of left superior temporal gyrus (STG) (200 ms), left precentral gyrus (250 ms, 400ms), and right inferior frontal gyrus (300, 450 ms) for disgust, and an enhancement of left cuneus (200 ms, 500 ms), left FuG (250ms), inferior frontal gyrus (250 ms), and right medial frontal gyrus (400 ms) for the happy compared to the neutral faces.The results of the study support the view that a combined fMRI and EEG approach of studying emotional perception enhances our knowledge about the time course of activation of different sources and reveals sources which have not reached significance in fMRI. The modality aspects of static compared to dynamic stimuli are discussed as well as functional aspects of sources in the context of e.g. disgust perception (insula), biological motion (STG), and facial identity perception (FuG).Dissertation329 156 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Temporo-Spatial Characteristics in Working Memory Processes Investigated with Static and Dynamic Complex Stimuli - Functional Magnetic Resonance Imaging, Event-Related Potentials and fMRI-Constrained Source Analysis(2008-11-24); ; ; Experiment 1:In the majority of experiments studying working memory (WM) tasks either delayed match-to-sample (DMTS) or n-back tasks were used to assess WM operations. In n-back tasks, however, a separation of different WM processes is impossible, whereas in DMTS tasks it is usually not required to monitor the WM content.In Experiment 1, a variant of a DMTS task with continuously morphing stimuli was applied, requiring human participants to continuously monitor and compare the currently presented stimulus to the held-in-mind target shape during the retention period. To asses changes caused by cognitive load two different types of stimuli were employed: Complex curved shapes and a simple circle. Furthermore four different delay durations (3, 6, 9, 12 s) have been applied. The goal of the present fMRI study was to characterize brain areas responsible for WM maintenance under continuous monitoring conditions in a WM task with morphing shapes. Moreover, the influence of cognitive load on maintenance activity in motion-sensitive area MT should be investigated. Data from 15 study participants are presented. Conjunction analysis including the contrasts complex versus simple shapes over all delay durations revealed activations in a widespread fronto-parietal network, which has been discussed to be involved in WM by a large body of literature. Area MT showed an association with target complexity, resulting in a significant signal enhancement while monitoring complex shapes (compared with simple circle trials).The present results demonstrate that the level of activation during the maintenance interval might be dependent on target complexity, because complex targets caused a stronger activation than simple circle targets in brain areas associated with WM processes even during similar visual stimulation.Experiment 2:So far, WM retrieval has been investigated only in a few studies. In Experiment 2, a DMTS task using static stimuli was applied to examine differences in the processing of different probe types (targets, non-targets) during the retrieval epoch. Probe stimuli were presented at different positions in the trial (trial position A, B, and C), resulting in parametrically increasing delay durations (3, 7, and 11 seconds) before probe presentation.Twenty individuals completed a similar WM task in an fMRI session as well as in an EEG session.The objective of the present study was to characterize differences in the cognitive processing of target probes and non-target probes by using different methodological approaches (behavioral, fMRI, EEG, and SA data) and to examine the influence of delay duration (cognitive load) on these differences.P3b mean amplitudes showed higher values for target trials compared with non-target trials at electrode position Cz, corroborating old/new effects reported from long-term memory research.The majority of brain regions which showed activation in fMRI in the probe epoch regardless of probe type (probe epoch versus fixation) did also show activation when contrasting target trials with non-target trials. This indicated a specific involvement of these brain areas in the processing of target stimuli. Altogether, behavioral, fMRI and EEG data indicated probe type-related processing differences, which might have been influenced by the ratio of target stimuli to non-target stimuli and also by the presence of distracting probe stimuli during longer delay periods (7, 11 s).Source analysis revealed a sequence of source activities during probe type processing starting with activity in occipital and temporal brain regions. This was presumably linked to the processing of stimulus features, followed by a simultaneous involvement of parietal and frontal brain regions and later processing in superior frontal gyrus (pre-SMA).Differences in source activity between targets and non-targets indicated a specific involvement of left fusiform gyrus in the non-target condition, probably associated with the mental imagination of the target stimulus during non-target probe processing.Furthermore, source activities showed specific engagements in target processing for the regional source in anterior cingulate cortex (ACC) before response execution and also for the regional source in superior frontal gyrus (SFG) before and simultaneously to response execution. These findings might be an indicator for the involvement of both regions in different stages of conflict managing operations because target trials had a lower stimulus frequency compared with non-target trials (at trial positions A and B).Summarized, different WM processes (maintenance, retrieval) were investigated in both experiments, and different methodological approaches were applied. In the general discussion, findings from both experiments are linked to each other, considering brain regions which were involved in the processing of both tasks.Dissertation313 136 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Neural correlates of decision making in quasi-realistic binary decision situations : an EEG and fMRI study(2019-11-07); ; ; A central aspect of daily life is decision making, often under uncertain and ill-defined conditions. This may be why there is huge and continuously growing scientific interest in human decision making. Research of decision making was dominated by mathematical and economic models at first, which led to abstract problems and decision situations, but recent years have seen a growing trend to orient research towards realistic scenarios. The relatively young branch of Naturalistic Decision Making (NDM) placed analyzing real world decision processes of experts at its very core and emphasizes the importance of recognizing the situation to come to a quick yet reliable decision. Uncertainty is a constant aspect of decision making and can be defined as a feeling of doubt that delays or impedes the decision. The aim of this study was to investigate the neural correlates of decision making under certainty and uncertainty in a quasi-realistic setting, that approached the principles of NDM as much as possible in neuroscience. Participants were presented with variations of a simple binary choice. Two types of information from different sources were presented to them: a weather forecast on the probability of rain and a picture of the sky. Based on this information the participants decided whether they would want to take an umbrella with them in a hypothetical context situation. This information varied in its conclusiveness and in its congruency, evoking either certainty or uncertainty in the decision makers, depending on their decision strategies. Each participant undertook the experiment twice; their neural activity was measured once with the EEG and once with fMRI. To account for said individual decision strategies, uncertain and certain decision making during the experiment was identified for each participant individually. This categorization was based on the congruency of the participants' choices. Multiple analyses were conducted to investigate the data, namely: statistical analyses of the behavioral data, including visualization and parameterization of decision strategies; a contrast and conjunction analysis of the fMRI data, and an additional analysis of individual voxel based activation; an ERP analysis, and a frequency analysis of the EEG data. Overall, this study has shown two things. One concerns the neural correlates of decision making: The processing of uncertain and certain decision making seems to have some differences, as addressed in the relevant literature, but seems to be mostly driven by the same fronto-parietal network. The second concerns the nature of quasi-realistic research, which seems to be possible in a laboratory context and offers much needed ecological validity, but requires attention to detail and individual variations. To properly use quasi-realistic designs, the standard procedures of analysis have to be adapted. During the analysis of the data, a number of limitations of the experimental design became apparent, mostly stemming from an initial underestimation of the participant's individually varying decision strategies. Many possible improvements and alternative approaches to design and analysis could be devised based on these realizations, which may be beneficial to future studies in this general field.Dissertation520 301 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Interference control in healthy and pathological ageing(2015-04-22); ; ; Age-associated cognitive decline is particularly pronounced in executive functions such as interference control - the ability to suppress the processing of irrelevant information. These deficits are also evident in patients with amnestic Mild Cognitive Impairment (aMCI), a preclinical phase of Alzheimer s dementia. In recent years, various studies have demonstrated that interference control consists of distinct subcomponents that are associated with different conflict tasks such as the Flanker conflict and the stimulus-response-conflict (SRC) task. Moreover, these subcomponents rely on distinct neural networks and exhibit specific temporal characteristics of neural processing. The present thesis investigates the effects of healthy and pathological ageing on different components of interference control. A combined Flanker and SRC task was conducted by young adults, healthy elderly and elderly with aMCI during electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) recording. Data analysis revealed that healthy elderly exhibit additional recruitment of fronto-parietal networks and increased modulation of the P2 component in response to incongruent information, probably as a compensatory mechanism. The deterioration of this effect in elderly with aMCI points to a decompensation in pathological ageing. Furthermore, the effects of healthy and pathological ageing on interference control are specific for different subcomponents, whereas SRC-related processing seems to be particularly susceptible to ageing effects.Dissertation290 226 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Cognitive Control of coherent motion perception:functional MRI studies of response selection(2008-08-13); ; ; Executive control is a human ability that allows to overcome automatic stimulus-responsemappings and to act appropriate in the context of a task where the selection of relevant stimuliand the suppression of interfering information are crucial. The first study (Chapter 2) aimed atcharacterizing the neural correlates of conflict resolution in two variations of the Simoneffect. Two different Simon tasks were introduced where subjects had to identify shapes onthe basis of form-from-motion perception (FFM) within a randomly moving dot field, while(1) motion direction (motion-based Simon task) or (2) stimulus location (location-basedSimon task) had to be ignored. Behavioral data revealed that both types of Simon tasksinduced highly significant interference effects. Using event-related fMRI we coulddemonstrate that both tasks share a common cluster of activated brain regions during conflictresolution (pre-supplementary motor area (pre-SMA), superior parietal lobule (SPL), andcuneus) but also show task-specific activation patterns (left superior temporal cortex in themotion-based, and the left fusiform gyrus in the location-based Simon task). Althoughmotion-based and location-based Simon tasks are conceptually very similar (Type-3 stimulusresponseensembles according to the taxonomy of Kornblum&Stevens (2002)) conflictresolution in both tasks results in the activation of different task-specific regions probablyrelated to the different sources of task-irrelevant information. The second experiment(Chapter 3) aimed at investigating the influence of the degree of interfering information onerror processing. The ability to detect errors is a crucial prerequisite for the appropriateadjustment of behavior to future situations. By means of fMRI, we provide evidence for theexistence of different error-related networks within the human brain. While errors related toincompatible trials were mainly associated with activation of the rostral anterior cingulatecortex (rACC) and the precuneus / posterior cingulate, errors related to trials without preresponseconflict showed specific activation in right inferior parietal cortex. Despite thisfunctional dissociation of brain networks, conjunction analysis revealed common clusters ofactivation in the medial wall (dorsal anterior cingulate cortex (dACC) and medial superiorfrontal cortex (msFC)), and bilateral inferior frontal gyrus / insula, consistent with earlierreports of error-related BOLD-signal increases. The results support the view that despite of anoverlapping core system of error processing, additional brain areas come into play dependingon the existence or absence of cognitive conflict. In order to address the question which brainareas are involved in the detection and processing of two simultaneously operating sources ofinterference derived from a spatial incompatibility task, we used fMRI to directly contrastneural activity related to a double conflict situation to single incompatibility conditions(Chapter 6). Results show signal increase of left dorsolateral prefrontal cortex whenmonitoring simultaneously presented conflict. There was no additional activity in the medialprefrontal cortex or anterior cingulate cortex although these regions are expected to play animportant role in all types of conflict monitoring. Further analyses also suggest a major rolefor the basal ganglia during error detection and resolution.Dissertation244 127 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Klinisch-neuropsychologische und funktionell-bildgebende Korrelate exekutiver Funktionen unter besonderer Berücksichtigung der Inhibitionskontrolle bei Parkinson-Patienten(2005-12-08); ; ; The predominance of executive dysfunctions in patients with Parkinson`s disease (PD) was frequently and consistently reported by neuropsychological and functional brain imaging studies. These disturbances are caused by pathophysiological changes in the dopaminergic system and related circuits linking subcortical and cortical regions, also affecting other neurotransmitter systems. The purpose of this project was the investigation of the neuropsychological profile of PD patients on one hand. On the other hand, neural correlates of interference control as one component of executive functions in healthy controls (young and old) and PD patients were studied using functional magnetic resonance imaging (fMRI) on a spatial stimulus-response compatibility task (Simon effect). Neuropsychologically, PD patients showed slowing in simple motor speed and deficits in measures of executive functioning. Using functional imaging and comparing neuronal patterns of activation during active inhibition, older subjects showed strong bilateral fronto-parietal cortical activations. Successful inhibition in PD patients was associated with focused activations in inferior frontal cortex, insular cortex and the cerebellum. Our findings in PD are discussed in terms of underlying pathophysiological changes, affecting normal functioning of brain networks.Dissertation318 200 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Berufliche Reintegration nach Hirnschädigung(2003-04-30); ; ; Return to work after brain injury is at high risk for failure. It is of critical interest for rehabilitation clinicians to know which key factors influence successful reintegration in working conditions. The vast majority of outcome studies focus solely on injury-related facts. Despite profound knowledge concerning the importance of individual psychological processes they are often neglected in scientific investigations. The aim of the present study was to identify the influence of those psychological processes, e.g. coping strategies, cognitive beliefs, and adaptation skills on successful return to work after neuropsychological rehabilitation. A hierarchical model is presented consisting of the components Potential , Psychic Executive , and Performance . Potential , subsuming demographic, clinical and functional data, is not supposed to directly influence Performance . Performance , the capability of a person to perform sufficiently in work, activities of daily living and therapy is presumed to be strongly determined by Psychic Executive . A cohort of 30 patients (mainly suffering from TBI and Stroke) from an outpatient clinic was comprehensively investigated. Psychic Executive at therapy onset showed a high predictive capability concerning patients Performance at the end of therapy. The self-ratings of activities of daily living turned out to be another important predictor for successful work re-entry. Due to the relatively small study sample the results can only be interpreted as temporary and heuristic. Despite this critique future outcome studies on return to work after brain injuries should urgently include psychological factors related to the rehabilitation process.Dissertation429 1278 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Semantische Interferenzkontrolle im episodischen Gedächtnis(2003-04-10); ; ; Episodic memory retrieval critically depends on the ability to use semantic knowledge. Thus, the investigation of memory performance on semantically related items is a powerful means by which interference effects can be evoked. Control of semantic interference involves executive processes such as monitoring and mobilisation of processing resources engaged in episodic memory retrieval (retrieval effort). The present study aimed to investigate neural correlates of semantic interference control processes using event-related functional magnetic resonance imaging (fMRI and event-related potentials (ERP). Subjects studied two word lists assigned to six semantic categories two of which were identical in each list (interference condition). During the test condition subjects performed source judgements on a mixture of both study lists and new words. Behavioural data demonstrated that semantic similarity induced highly reliable semantic interference effects: source attributions of semantically related items resulted in significantly longer reaction times and higher error rates compared to the non-interference condition.The fMRI-study revealed an interference-specific activation pattern in right ventrolateral (VLPFC) and left dorsolateral prefrontal (DLPFC) cortex. We suggest that VLPFC activity reflects neuronal activity associated with both specification of retrieval cues and inhibition of irrelevant information while DLPFC mediates recollection monitoring. ERP analysis showed no significant main effect of interference condition. A median split was used to separate subjects with high and low retrieval effort. Only subjects with large differences in reaction times for the interference condition compared to the control condition showed left frontal ERPs that were more positive-going for the interference condition compared to the non-interference condition. These differences were interpreted as reflecting processes associated with retrieval effort.Dissertation364 246