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Gen-Umwelt-Interaktionen haben einen wichtigen Stellenwert für das Verständnis der Entstehung psychiatrischer Erkrankungen. Für die Catechol-O-Methyltransferase (COMT)konnte kürzlich gezeigt werden, dass diese die Gehirnaktivität moduliert, während der Verarberitung negativer Stimuli. Für positive Stimuli konnte kein Effekt nachgewiesen werden. In der vorliegenden Arbeit sollte nun geprüft werden, ob Lebensereignisse, als ein Umweltfaktor, für die emotionale Verarbeitung eine Rolle spielen. Um das herauszufinden untersuchten wir 81 gesunde Probanden mittels EEG während der Darbietung positiver und negativer emotionaler Bilder. Wie erwartet moduliert COMT die EPN (early posterior negativity) für negative Bilder, aber nicht für positive. Unter Berücksichtigung der Lebensereignisse konnte der fehlende Effekt der COMT bei der positiven Bedingung aufgelöst werden. Eine hohe Lebensereignis-Last führt dabei zu einer verminderten Gehirnaktivität für positive Stimuli, was sich aber nur für den Met/Met-Genotyp zeigt. Relevant scheint das vor allem für die Entwicklung von Depressionen zu sein, da depressive Patienten häufig ihre Umwelt als weniger positiv bewerten.
Einleitung: SSEP sind etabliert, um Patienten intraoperativ zu überwachen, wenn sie sich Operationen im zerebrovaskulären System unterziehen. Das EEG ist eine weitere Methode zur neurophysiologischen Überwachung. In dieser Studie wurde die Wertigkeit des simultanen Ableitens von SSEP und EEG Signalen untersucht. Methode: Dreizehn Patienten (7 Frauen, 6 Männer, mittleres Alter 53.5 Jahre), welche sich dem Clipping eines intrakraniellen Aneurysma unterzogen, wurden eingeschlossen. Die SSEP Latenz 1 (Lat1), Latenz 2 (Lat2) und Amplitude (Amp) wurden kontinuierlich gemessen. Verminderung der Amplitude > 50% oder Verlängerungen der Latenzen > 10% gegenüber den Ausgangswerten wurden als signifikante Ereignisse bewertet. Das EEG wurde mittels einer subduralen Grid-Elektrode gemessen. Alpha % (Al%), Alpha-Delta-Ratio (ADR) und Total Power (TP) wurden ausgewertet. Resultate: Circa 9000 Einzelwerte wurden analysiert. Statistisch signifikante Korrelationen traten zwischen Al% und Amp (K=0.5) auf. Dabei zeigten sich die Veränderungen im EEG (Al%) 6 Minuten vor Ereignissen im SSEP (Amp). Statistisch signifikante Korrelationen traten ebenfalls zwischen Al% und Amp-Ereignissen (K=-0.4) auf. In 6/7 Patienten traten die Al%-Änderungen 7 Minuten vor den Amp-Änderungen auf. Noch stärkere Beziehungen ergaben sich zwischen Lat2 und allen EEG Modalitäten, jedoch reichte die Gesamtzahl der Datenpunkte nicht aus, um statistische Signifikanzen herzuleiten. Schlussfolgerung: Dies ist die erste Beschreibung von signifikanten Beziehungen zwischen quantitativem SSEP und EEG während zerebrovaskulären Operationen. Das quantitative EEG hat das Potenzial, frühe ischämische Ereignisse eher zu detektieren als dies mit SSEP möglich ist.
The present dissertation aims to shed light on different mechanisms of socio-emotional feedback in social decision-making situations. The objective is to evaluate emotional facial expressions as feedback stimuli, i.e., responses of interaction partners to certain social decisions. In addition to human faces, artificial emojis are also examined due to their relevance for modern digital communication. Previous research on the influence of emotional feedback suggests that a person's behavior can be effectively reinforced by rewarding stimuli. In the context of this dissertation, the differences in the feedback processing of human photographs and emojis, but also the evaluation of socially expected versus socially unexpected feedback were examined in detail in four studies. In addition to behavioral data, we used the electroencephalogram (EEG) in all studies to investigate neural correlates of social decision-making and emotional feedback.
As the central paradigm, all studies were based on a modified ultimatum game. The game is structured as follows: there is a so-called proposer who holds a specific amount of money (e.g., 10 cents) and offers the responder a certain amount (e.g., 3 cents). The responder then decides whether to accept or reject the offer. In the version of the ultimatum game presented here, different types of proposers are introduced. After the participants have accepted or rejected in the role of the responder, the different proposers react to the participant’s decision with specific emotional facial expressions. Different feedback patterns are used for the individual experiments conducted in the course of this dissertation.
In the first study, we investigated the influence of emotional feedback on decision-making in the modified version of the ultimatum game. We were able to show that a proposer who responds to the acceptance of an offer with a smiling face achieves more accepted offers overall than a control proposer who responds to both accepted and rejected offers with a neutral facial expression. Consequently, the smile served as a positive reinforcement. Similarly, a sad expression in response to a rejected offer also resulted in higher acceptance rates as compared to the control identity, which could be considered an expression of compassion for that proposer. On a neuronal level, we could show that there are differences between simply looking at negative emotional stimuli (i.e., sad and angry faces) and their appearance as feedback stimuli after rejected offers in the modified ultimatum game. The so-called feedback-related negativity was reduced (i.e., more positive) when negative emotions appeared as feedback from the proposers. We argued that these findings might show that the participants wanted to punish the proposers by rejecting an offer for its unfairness and therefore the negative feedback met their expectations. The altered processing of negative emotional facial expressions in the ultimatum game could therefore indicate that the punishment is interpreted as successful. This includes the expectation that the interaction partner will change his behavior in the future and eventually make fairer offers.
In the second study we wanted to show that smiling and sad emojis as feedback stimuli in the modified ultimatum game can also lead to increased acceptance rates. Contrary to our assumptions, this effect could not be observed. At the neural level as well, the findings did not correspond to our assumptions and differed strongly from those of the first study. One finding, however, was that the neural P3 component showed how the use of emojis as feedback stimuli particularly characterizes certain types of proposers. This is supported by the fact that the P3 is increased for the proposer who rewards an acceptance with a smile as well as for the proposer who reacts to rejection with a sad emoji compared to the neutral control proposer.
The third study examined the discrepancy between the findings of the first and second study. Accordingly, both humans and emojis representing the different proposers were presented in the ultimatum game. In addition, emojis were selected that showed a higher similarity to known emojis from common messenger services compared to the second study. We were able to replicate that the proposers in the ultimatum game, who reward an acceptance of the offer with a smile, led to an increased acceptance rate compared to the neutral control proposers. This difference is independent of whether the proposers are represented by emojis or human faces. With regard to the neural correlates, we were able to demonstrate that emojis and human faces differ strongly in their neural processing. Emojis showed stronger activation than human faces in the face-processing N170 component, the feedback-related negativity and the P3 component. We concluded that the results of the N170 and feedback-related negativity could indicate a signal for missing social information of emojis compared to faces. The increased P3 amplitude for emojis might imply that emojis appear unexpectedly as reward stimuli in a social decision task compared to human faces.
The last study of this project dealt with socially unexpected feedback. In comparison to the first three studies, new proposer identities were implemented. In particular, the focus was on a proposer who reacted to the rejection of an offer unexpectedly with a smile and to the acceptance with a neutral facial expression. According to the results, participants approach this unexpected smile through increased rejection, although it is accompanied by financial loss. In addition, as reported in studies one and three, we were able to show that proposers who respond to the acceptance of an offer with a smiling face and thus meet the expectations of the participants have higher offer acceptance rates than the control proposer. At the neuronal level, especially the feedback from the socially unexpected proposer led to an increased P3 amplitude, which indicates that smiling after rejection is attributed a special subjective importance.
The experiments provide new insights into the social influence through emotional feedback and the processing of relevant social cues. Due to the conceptual similarity of the studies, it was possible to differentiate between stable findings and potentially stimulus-dependent deviations, thus creating a well-founded contribution to the current research. Therefore, the novel paradigm presented here, and the knowledge gained from it could also play an important role in the future for clinical questions dealing with limited social competencies.
The maximum of the brain electrical field after NoGo stimuli is located more anteriorly than that after stimuli that tells participants to respond. The difference in topography was called NoGo-Anteriorization (NGA). Recently, there was a debate, whether the NGA is related to a central inhibitory process or not. However, experiments showed that the NGA is not the result of motor potentials during Go trials, the NGA does not represent higher response conflict and or higher mental effort in NoGo trials, and the NGA is not based on less cognitive response selection in NoGo trials. Therefore, the experiments support the assumption that the NGA is connected to an inhibitory mechanism in NoGo conditions.
Recent research suggests that the P3b may be closely related to the activation of the locus coeruleus-norepinephrine (LC-NE) system. To further study the potential association, we applied a novel technique, the non-invasive transcutaneous vagus nerve stimulation (tVNS), which is speculated to increase noradrenaline levels. Using a within-subject cross-over design, 20 healthy participants received continuous tVNS and sham stimulation on two consecutive days (stimulation counterbalanced across participants) while performing a visual oddball task. During stimulation, oval non-targets (standard), normal-head (easy) and rotated-head (difficult) targets, as well as novel stimuli (scenes) were presented. As an indirect marker of noradrenergic activation we also collected salivary alpha-amylase (sAA) before and after stimulation. Results showed larger P3b amplitudes for target, relative to standard stimuli, irrespective of stimulation condition. Exploratory post hoc analyses, however, revealed that, in comparison to standard stimuli, easy (but not difficult) targets produced larger P3b (but not P3a) amplitudes during active tVNS, compared to sham stimulation. For sAA levels, although main analyses did not show differential effects of stimulation, direct testing revealed that tVNS (but not sham stimulation) increased sAA levels after stimulation. Additionally, larger differences between tVNS and sham stimulation in P3b magnitudes for easy targets were associated with larger increase in sAA levels after tVNS, but not after sham stimulation. Despite preliminary evidence for a modulatory influence of tVNS on the P3b, which may be partly mediated by activation of the noradrenergic system, additional research in this field is clearly warranted. Future studies need to clarify whether tVNS also facilitates other processes, such as learning and memory, and whether tVNS can be used as therapeutic tool.
Gambling is a popular activity in Germany, with 40% of a representative sample reporting having gambled at least once in the past year (Bundeszentrale für gesundheitliche Aufklärung, 2014). While the majority of gamblers show harmless gambling behavior, a subset develops serious problems due to their gambling, affecting their psychological well-being, social life and work. According to recent estimates, up to 0.8% of the German population are affected by such pathological gambling. People in general and pathological gamblers in particular show several cognitive distortions, that is, misconceptions about the chances of winning and skill involvement, in gambling. The current work aimed at elucidating the biopsychological basis of two such kinds of cognitive distortions, the illusion of control and the gambler’s and hot hand fallacies, and their modulation by gambling problems. Therefore, four studies were conducted assessing the processing of near outcomes (used as a proxy for the illusion of control) and outcome sequences (used as a proxy for the gambler’s and hot hand fallacies) in samples of varying degrees of gambling problems, using a multimethod approach.
The first study analyzed the processing and evaluation of near outcomes as well as choice behavior in a wheel of fortune paradigm using electroencephalography (EEG). To assess the influence of gambling problems, a group of problem gamblers was compared to a group of controls. The results showed that there were no differences in the processing of near outcomes between the two groups. Near compared to full outcomes elicited smaller P300 amplitudes. Furthermore, at a trend level, the choice behavior of participants showed signs of a pattern opposite to the gambler’s fallacy, with longer runs of an outcome color leading to increased probabilities of choosing this color again on the subsequent trial. Finally, problem gamblers showed smaller feedback-related negativity (FRN) amplitudes relative to controls.
The second study also targeted the processing of near outcomes in a wheel of fortune paradigm, this time using functional magnetic resonance imaging and a group of participants with varying degrees of gambling problems. The results showed increased activity in the bilateral superior parietal cortex following near compared to full outcomes.
The third study examined the peripheral physiology reactions to near outcomes in the wheel of fortune. Heart period and skin conductance were measured while participants with varying degrees of gambling problems played on the wheel of fortune. Near compared to full outcomes led to increased heart period duration shortly after the outcome. Furthermore, heart period reactions and skin conductance responses (SCRs) were modulated by gambling problems. Participants with high relative to low levels of gambling problems showed increased SCRs to near outcomes and similar heart period reactions to near outcomes and full wins.
The fourth study analyzed choice behavior and sequence effects in the processing of outcomes in a coin toss paradigm using EEG in a group of problem gamblers and controls. Again, problem gamblers showed generally smaller FRN amplitudes compared to controls. There were no differences between groups in the processing of outcome sequences. The break of an outcome streak led to increased power in the theta frequency band. Furthermore, the P300 amplitude was increased after a sequence of previous wins. Finally, problem gamblers compared to controls showed a trend of switching the outcome symbol relative to the previous outcome symbol more often.
In sum, the results point towards differences in the processing of near compared to full outcomes in brain areas and measures implicated in attentional and salience processes. The processing of outcome sequences involves processes of salience attribution and violation of expectations. Furthermore, problem gamblers seem to process near outcomes as more win-like compared to controls. The results and their implications for problem gambling as well as further possible lines of research are discussed.
Spontaneous brain activity builds the foundation for human cognitive processing during external demands. Neuroimaging studies based on functional magnetic resonance imaging (fMRI) identified specific characteristics of spontaneous (intrinsic) brain dynamics to be associated with individual differences in general cognitive ability, i.e., intelligence. However, fMRI research is inherently limited by low temporal resolution, thus, preventing conclusions about neural fluctuations within the range of milliseconds. Here, we used resting-state electroencephalographical (EEG) recordings from 144 healthy adults to test whether individual differences in intelligence (Raven’s Advanced Progressive Matrices scores) can be predicted from the complexity of temporally highly resolved intrinsic brain signals. We compared different operationalizations of brain signal complexity (multiscale entropy, Shannon entropy, Fuzzy entropy, and specific characteristics of microstates) regarding their relation to intelligence. The results indicate that associations between brain signal complexity measures and intelligence are of small effect sizes (r ∼ 0.20) and vary across different spatial and temporal scales. Specifically, higher intelligence scores were associated with lower complexity in local aspects of neural processing, and less activity in task-negative brain regions belonging to the default-mode network. Finally, we combined multiple measures of brain signal complexity to show that individual intelligence scores can be significantly predicted with a multimodal model within the sample (10-fold cross-validation) as well as in an independent sample (external replication, N = 57). In sum, our results highlight the temporal and spatial dependency of associations between intelligence and intrinsic brain dynamics, proposing multimodal approaches as promising means for future neuroscientific research on complex human traits.
The effect of inherently threatening contexts on visuocortical engagement to conditioned threat
(2023)
Fear and anxiety are crucial for adaptive responding in life‐threatening situations. Whereas fear is a phasic response to an acute threat accompanied by selective attention, anxiety is characterized by a sustained feeling of apprehension and hypervigilance during situations of potential threat. In the current literature, fear and anxiety are usually considered mutually exclusive, with partially separated neural underpinnings. However, there is accumulating evidence that challenges this distinction between fear and anxiety, and simultaneous activation of fear and anxiety networks has been reported. Therefore, the current study experimentally tested potential interactions between fear and anxiety. Fifty‐two healthy participants completed a differential fear conditioning paradigm followed by a test phase in which the conditioned stimuli were presented in front of threatening or neutral contextual images. To capture defense system activation, we recorded subjective (threat, US‐expectancy), physiological (skin conductance, heart rate) and visuocortical (steady‐state visual evoked potentials) responses to the conditioned stimuli as a function of contextual threat. Results demonstrated successful fear conditioning in all measures. In addition, threat and US‐expectancy ratings, cardiac deceleration, and visuocortical activity were enhanced for fear cues presented in threatening compared with neutral contexts. These results are in line with an additive or interactive rather than an exclusive model of fear and anxiety, indicating facilitated defensive behavior to imminent danger in situations of potential threat.
Anxiety is characterized by anxious anticipation and heightened vigilance to uncertain threat. However, if threat is not reliably indicated by a specific cue, the context in which threat was previously experienced becomes its best predictor, leading to anxiety. A suitable means to induce anxiety experimentally is context conditioning: In one context (CTX+), an unpredictable aversive stimulus (US) is repeatedly presented, in contrast to a second context (CTX−), in which no US is ever presented. In this EEG study, we investigated attentional mechanisms during acquisition and extinction learning in 38 participants, who underwent a context conditioning protocol. Flickering video stimuli (32 s clips depicting virtual offices representing CTX+/−) were used to evoke steady‐state visual evoked potentials (ssVEPs) as an index of visuocortical engagement with the contexts. Analyses of the electrocortical responses suggest a successful induction of the ssVEP signal by video presentation in flicker mode. Furthermore, we found clear indices of context conditioning and extinction learning on a subjective level, while cortical processing of the CTX+ was unexpectedly reduced during video presentation. The differences between CTX+ and CTX− diminished during extinction learning. Together, these results indicate that the dynamic sensory input of the video presentation leads to disruptions in the ssVEP signal, which is greater for motivationally significant, threatening contexts.
Adapting defensive behavior to the characteristics of a threatening situation is a fundamental function of the brain. Particularly, threat imminence plays a major role for the organization of defensive responses. Acute threat prompts phasic physiological responses, which are usually associated with an intense feeling of fear. In contrast, diffuse and potentially threatening situations elicit a sustained state of anxious apprehension. Detection of the threatening stimulus defines the key event in this framework, initiating the transition from potential to acute threat. Consequently, attention to threat is crucial for supporting defensive behavior. The functions of attention are finely tuned to the characteristics of a threatening situation. Potential threat is associated with hypervigilance, in order to facilitate threat detection. Once a threatening stimulus has been identified, attention is selectively focused on the source of danger. Even though the concepts of selective attention and hypervigilance to threat are well established, evidence for their neural correlates remain scarce. Therefore, a major goal of this thesis is to elucidate the neural correlates of selective attention to acute threat and hypervigilance during potential threat. A second aim of this thesis is to provide a mechanistic account for the interaction of fear and anxiety. While contemporary models view fear and anxiety as mutually exclusive, recent findings for the neural networks of fear and anxiety suggest potential interactions. In four studies, aversive cue conditioning was used to induce acute threat, while context conditioning served as a laboratory model of potential threat. To quantify neural correlates of selective attention and hypervigilance, steady-state visual evoked potentials (ssVEPs) were measured as an index of visuocortical responding. Study 1 compared visuocortical responses to acute and potential threat for high versus low trait-anxious individuals. All individuals demonstrated enhanced electrocortical responses to the central cue in the acute threat condition, suggesting evidence for the neural correlate of selective attention. However, only low anxious individuals revealed facilitated processing of the contexts in the potential threat condition, reflecting a neural correlate of hypervigilance. High anxious individuals did not discriminate among contexts. These findings contribute to the notion of aberrational processing of potential threat for high anxious individuals. Study 2 and 3 realized orthogonal combinations of cue and context conditioning to investigate potential interactions of fear and anxiety. In contrast to Study 1 and 2, Study 3 used verbal instructions to induce potentially threatening contexts. Besides ssVEPs, threat ratings and skin conductance responses (SCRs) were recorded as efferent indices of defensive responding. None of these studies found further evidence for the neural correlates of hypervigilance and selective attention. However, results for ratings and SCRs revealed additive effects of fear and anxiety, suggesting that fear and anxiety are not mutually exclusive, but interact linearly to organize and facilitate defensive behavior. Study 4 tested ssVEPs to more ecologically valid forms of context conditioning, using flickering video stimuli of virtual offices to establish context representations. Contrary to expectations, results revealed decreased visuocortical responses during sustained presentations of anxiety compared to neutral contexts. A disruption of ssVEP signals eventually suggests interferences by continuously changing video streams which are enhanced as a function of motivational relevance. In summary, this thesis provided evidence for the neural correlates of attention only for isolated forms of fear and anxiety, but not for their interaction. In contrast, an additive interaction model of fear and anxiety for measures of defensive responding offers a new perspective on the topography of defensive behavior.
Für den Bispektral Index (BIS) ist eine gute Korrelation zum Grad der Sedierung, hervorgerufen durch unterschiedliche Sedativa wie auch zum Teil in Verbindung mit Opioiden, nachgewiesen [16]. Ziel dieser prospektiven Studie war es, die Eignung des BIS für das Sedationsmonitoring auf der Intensivstation zu überprüfen, da hier nach wie vor mangels valider Überwachungssysteme hauptsächlich klinische Scoringverfahren zum Einsatz kommen. Nach Zustimmung der örtlichen Ethikkommission wurde bei 19 beatmeten, operativen Intensivpatienten ohne zentralneurologische Vorerkrankungen zweimal täglich bis zur Extubation der BIS Vs. 3.11 (Aspect Medical Systems, Natick, MA, USA) soweit der entsprechende Score der modifizierten Ramsay-Scale, Cook-Scale, Glasgow-Coma-Scale, Sedation-/Agitation-Scale und der Obeserver´s Assessment of Altertness Scale erhoben und miteinander korreliert. Erfasst wurden ferner alle Labor- und Kreislaufparameter wie auch die Medikation. Insgesamt wurden 247 Messungen durchgeführt. Nur bei 11 von 19 Patienten (58%) lässt sich eine positive Korrelation zwischen BIS und allen Scores zeigen (0.64    0,7, p < 0,0001). Verlässliche Hinweise zur Unterscheidung zwischen Patienten mit und ohne Korrelation zeigten sich nach 4–15 Messungen (Mittel 8,4). Bei Patienten mit Korrelation waren die Steigungen der jeweiligen Regressionsgeraden signifikant verschieden voneinander (p < 0,05).
3D visualization of movements can amplify motor cortex activation during subsequent motor imagery
(2015)
A repetitive movement practice by motor imagery (MI) can influence motor cortical excitability in the electroencephalogram (EEG). This study investigated if a realistic visualization in 3D of upper and lower limb movements can amplify motor related potentials during subsequent MI. We hypothesized that a richer sensory visualization might be more effective during instrumental conditioning, resulting in a more pronounced event related desynchronization (ERD) of the upper alpha band (10–12 Hz) over the sensorimotor cortices thereby potentially improving MI based brain-computer interface (BCI) protocols for motor rehabilitation. The results show a strong increase of the characteristic patterns of ERD of the upper alpha band components for left and right limb MI present over the sensorimotor areas in both visualization conditions. Overall, significant differences were observed as a function of visualization modality (VM; 2D vs. 3D). The largest upper alpha band power decrease was obtained during MI after a 3-dimensional visualization. In total in 12 out of 20 tasks the end-user of the 3D visualization group showed an enhanced upper alpha ERD relative to 2D VM group, with statistical significance in nine tasks.With a realistic visualization of the limb movements, we tried to increase motor cortex activation during subsequent MI. The feedback and the feedback environment should be inherently motivating and relevant for the learner and should have an appeal of novelty, real-world relevance or aesthetic value (Ryan and Deci, 2000; Merrill, 2007). Realistic visual feedback, consistent with the participant’s MI, might be helpful for accomplishing successful MI and the use of such feedback may assist in making BCI a more natural interface for MI based BCI rehabilitation.
Feedback efficiency and training effects during alpha band modulation over the sensorimotor cortex
(2015)
Neural oscillations can be measured by electroencephalography (EEG) and these oscillations can be characterized by their frequency, amplitude and phase. The mechanistic properties of neural oscillations and their synchronization are able to explain various aspects of many cognitive functions such as motor control, memory, attention, information transfer across brain regions, segmentation of the sensory input and perception (Arnal and Giraud, 2012). The alpha band frequency is the dominant oscillation in the human brain. This oscillatory activity is found in the scalp EEG at frequencies around 8-13 Hz in all healthy adults (Makeig et al., 2002) and considerable interest has been generated in exploring EEG alpha oscillations with regard to their role in cognitive (Klimesch et al., 1993; Hanselmayr et al., 2005), sensorimotor (Birbaumer, 2006; Sauseng et al., 2009) and physiological (Lehmann, 1971; Niedermeyer, 1997; Kiyatkin, 2010) aspects of human life. The ability to voluntarily regulate the alpha amplitude can be learned with neurofeedback training and offers the possibility to control a brain-computer interface (BCI), a muscle independent interaction channel. BCI research is predominantly focused on the signal processing, the classification and the algorithms necessary to translate brain signals into control commands than on the person interacting with the technical system. The end-user must be properly trained to be able to successfully use the BCI and factors such as task instructions, training, and especially feedback can therefore play an important role in learning to control a BCI (Neumann and Kübler, 2003; Pfurtscheller et al., 2006, 2007; Allison and Neuper, 2010; Friedrich et al., 2012; Kaufmann et al., 2013; Lotte et al., 2013).
The main purpose of this thesis was to investigate how end-users can efficiently be trained to perform alpha band modulation recorded over their sensorimotor cortex. The herein presented work comprises three studies with healthy participants and participants with schizophrenia focusing on the effects of feedback and training time on cortical activation patterns and performance. In the first study, the application of a realistic visual feedback to support end-users in developing a concrete feeling of kinesthetic motor imagery was tested in 2D and 3D visualization modality during a single training session. Participants were able to elicit the typical event-related desynchronisation responses over sensorimotor cortex in both conditions but the most significant decrease in the alpha band power was obtained following the three-dimensional realistic visualization. The second study strengthen the hypothesis that an enriched visual feedback with information about the quality of the input signal supports an easier approach for motor imagery based BCI control and can help to enhance performance. Significantly better performance levels were measurable during five online training sessions in the groups with enriched feedback as compared to a conventional simple visual feedback group, without significant differences in performance between the unimodal (visual) and multimodal (auditory–visual) feedback modality. Furthermore, the last study, in which people with schizophrenia participated in multiple sessions with simple feedback, demonstrated that these patients can learn to voluntarily regulate their alpha band. Compared to the healthy group they required longer training times and could not achieve performance levels as high as the control group. Nonetheless, alpha neurofeedback training lead to a constant increase of the alpha resting power across all 20 training session.
To date only little is known about the effects of feedback and training time on BCI performance and cortical activation patterns. The presented work contributes to the evidence that healthy individuals can benefit from enriched feedback: A realistic presentation can support participants in getting a concrete feeling of motor imagery and enriched feedback, which instructs participants about the quality of their input signal can give support while learning to control the BCI. This thesis demonstrates that people with schizophrenia can learn to gain control of their alpha oscillations recorded over the sensorimotor cortex when participating in sufficient training sessions. In conclusion, this thesis improved current motor imagery BCI feedback protocols and enhanced our understanding of the interplay between feedback and BCI performance.
Brain-computer interfaces (BCIs) can serve as muscle independent communication aids. Persons, who are unable to control their eye muscles (e.g., in the completely locked-in state) or have severe visual impairments for other reasons, need BCI systems that do not rely on the visual modality. For this reason, BCIs that employ auditory stimuli were suggested. In this study, a multiclass BCI spelling system was implemented that uses animal voices with directional cues to code rows and columns of a letter matrix. To reveal possible training effects with the system, 11 healthy participants performed spelling tasks on 2 consecutive days. In a second step, the system was tested by a participant with amyotrophic lateral sclerosis (ALS) in two sessions. In the first session, healthy participants spelled with an average accuracy of 76% (3.29 bits/min) that increased to 90% (4.23 bits/min) on the second day. Spelling accuracy by the participant with ALS was 20% in the first and 47% in the second session. The results indicate a strong training effect for both the healthy participants and the participant with ALS. While healthy participants reached high accuracies in the first session and second session, accuracies for the participant with ALS were not sufficient for satisfactory communication in both sessions. More training sessions might be needed to improve spelling accuracies. The study demonstrated the feasibility of the auditory BCI with healthy users and stresses the importance of training with auditory multiclass BCIs, especially for potential end-users of BCI with disease.
Der Einfluss von Aufmerksamkeit und Interferenzkontrolle auf die Verarbeitung visueller Stimuli
(2008)
Gegenstand der vorliegenden Arbeit war die Frage, inwieweit die neuronale Verarbeitung visueller Stimuli durch Prozesse der Aufmerksamkeit und des Arbeitsgedächtnisses moduliert werden kann. Darüber hinaus wurde untersucht, welche „top down“ Prozesse diese Modulation steuern. Dabei wurden zwei konkurrierende Ansichten als mögliche Erklärungsmodelle zugrunde gelegt und überprüft. Zum einen wäre es möglich, dass selektive Aufmerksamkeit zwei qualitativ unterschiedliche Mechanismen beinhaltet. Demnach würde neben dem Fokussieren auf relevante Informationen auch ein aktiver Prozess der Inhibition der Verarbeitung irrelevanter Stimuli existieren. Zum anderen ist es aber auch denkbar, dass aufgrund begrenzter Verarbeitungsressourcen das Fokussieren auf relevante Reize automatisch mit dem Nichtbeachten irrelevanter Stimuli einhergeht und nur ein Mechanismus existiert. In einem ersten Experiment wurde vorab die Alertness als ein grundlegender Prozess der Aufmerksamkeit mit der Nah-Infrarot Spektroskopie (NIRS) untersucht. Mittels eines zweigestuften Studiendesigns wurden in einem ersten Schritt für die Alertness relevante Regionen über fronto-temporalen Hirnarealen definiert. Als relevant erwiesen sich Areale des mittleren und superioren temporalen Kortex der rechten Hemisphäre und der ventrale Teil des inferioren frontalen Kortex der linken Hemisphäre. In einer zweiten Datenerhebung konnte für diese Regionen eine signifikant höhere Aktivierung während der Alertnessbedingung im Vergleich zu einer visuellen und motorischen Kontrollbedingung gefunden werden. Mit dem zweiten Experiment sollten bestehende, mit dem Elektroenzephalogramm (EEG) erhobene, Befunde zur Modulation der neuronalen Verarbeitung visueller Stimuli repliziert werden. Dies geschah mithilfe eines neu entwickelten Untersuchungsparadigmas, einer modifizierten n-back Aufgabe. Wie erwartet fand sich eine erhöhte Verarbeitung aufgaben-relevanter Reize im Vergleich zu einer perzeptuellen Kontrollbedingung. Die Verarbeitung irrelevanter Reize wurde allerdings nicht unterdrückt. Explorativ fand sich ein entsprechendes Korrelat der Aufmerksamkeitslenkung über frontalen Elektroden. In einem dritten Experiment wurde das modifizierte n-back Paradigma an die Anforderungen einer NIRS Messung angepasst, um frontale Effekte der Aufmerksamkeitslenkung direkter erfassen zu können als mit dem EEG. Wie erwartet fand sich bezüglich des Beachtens wie auch des Ignorierens von Stimuli eine Beteiligung frontaler Strukturen. Auf beachtete Stimuli folgte eine bilaterale Aktivierung des dorsolateralen präfrontalen Kortex (DL-PFK) und eine Aktivierung des linken inferioren frontalen Kortex bis hin zum prä- und postzentralen Kortex. Das Ignorieren visueller Stimuli führte zu einer weitläufigen Aktivierung des rechten präfrontalen Kortex (PFK). Eine Beteiligung des linken inferioren frontalen Gyrus an der Interferenzkontrolle konnte nicht wie erwartet nachgewiesen werden. Der Vergleich der beiden Aktivierungsmuster ergab keine signifikanten Unterschiede. Die zugrunde liegenden Prozesse des Arbeitsgedächtnisses und der Interferenzkontrolle führten also zu einer Aktivierung stark überlappender Hirnregionen. Nachdem die Ergebnisse der Experimente 2 und 3 keinerlei Hinweise auf einen aktiven Prozess der Interferenzinhibition nachweisen konnten, wurde im Experiment 4 die bisher genutzte 1-back Aufgabe durch eine schwierigere 2-back Aufgabe ersetzt. Aufgrund der erhöhten Auslastung des Arbeitsgedächtnisses sollte eine stärkere Anstrengung und damit eine verstärkte frontale Aktivierung bei der Interferenzinhibition auftreten. Diese Hypothese wurde mit einer frontalen NIRS Messung überprüft (Experiment 4a). Wie erwartet führte die erhöhte Auslastung des Arbeitsgedächtnisses zu einer verstärkten Aktivierung des PFK bezüglich beachteter Reize. Hinsichtlich ignorierter Reize fand sich allerdings keine frontale Beteiligung. Parallel erhobene EEG Daten zeigten keinen Unterschied zwischen der Verarbeitung beachteter und ignorierter Gesichter. Die Verarbeitung passiv betrachteter Gesichter war im Gegensatz zu beachteten und ignorierten Gesichtern vermindert. Im zweiten Teil der Studie (Experiment 4b) wurden erstmals die okzipitalen Effekte der Aufmerksamkeitslenkung mit der NIRS erfasst. Im Einklang mit den Ergebnissen der ersten EEG Studie (Experiment 2) fand sich zwar eine verstärkte Verarbeitung beachteter, aber keine verminderte Verarbeitung ignorierter Reize. Zusammengenommen sprechen die fehlende aktive Inhibition von Distraktorreizen im okzipitalen Kortex und die vergleichbaren neuronalen Korrelate von Prozessen des Arbeitsgedächtnisses und der Interferenzinhibition im frontalen Kortex für die Hypothese einer Aufteilung von begrenzten Verarbeitungsressourcen zugunsten beachteter Reize.
ZIELSETZUNG Die Aufmerksamkeitsdefizit-/Hyperaktivitätsstörung beinhaltet in ihrer Kernsymptomatik eine Störung der Motorik. Bisher wurden viele Studien zur motorischen Inhibition veröffentlich, wenige jedoch zur Exekution von motorischen Aufgaben. Im der vorliegenden Studie wurden Kinder und Jugendliche mit ADHS und gesunde Kontrollprobanden mittels zweier Aufgaben zur repetitiven Fingerbewegung untersucht. Zeitgleich wurden die Gehirndurchblutung mittels fNIRS sowie die neuronale Aktivität mittels EEG registriert. Ziel unserer Arbeit war es, die Ergebnisse von Romanos et al. (2007) zu replizieren sowie weitere Erkenntnisse über die Korrelation zwischen fNIRS- und EEG-Aktivierungen zu erlangen.
METHODEN Die Patientengruppe wurde jeweils einmal mit und einmal ohne Medikation gemessen, die Kontrollgruppe nur einmal. Die Kinder wurden nach entsprechender Aufklärung mit EEG- und fNIRS-Messeinrichtungen vorbereitet und führten nach einem kurzen Probedurchlauf einfach motorische Fingerbewegungen durch. Es wurden sowohl eine Finger-Daumen-Opposition als auch ein Zeigefinger-Tapping in einem bestimmten Rhythmus und Reihenfolge verlangt. Ergänzend wurde ein Oberflächen-EMG im Bereich der beteiligten Muskulatur am Unterarm aufgezeichnet. EEG-, fNIRS- und EMG-Ergebnisse wurden gemittelt und die unterschiedlichen Gruppen miteinander verglichen.
ERGEBNISSE In unserer Auswertung waren 24 Kinder mit der Diagnose einer ADHS sowie eine nach Alter und IQ vergleichbare Kontrollgruppe mit 16 Kindern. Das mittlere Alter betrug 12,4 (ADHS-Patienten) bzw. 12,10 Jahre (Kontrollen). Aufgrund einer ungleichen Geschlechterverteilung musste das Geschlecht als Kovariate in der Auswertung berücksichtigt werden. Wir konnten sowohl für die fNIRS als auch für die EEG typische Aktivierungsmuster feststellen. Für die medizierten Probanden fanden wir untypische, diffusere Aktivierung außerhalb des Bereichs des Motorkortex mit fNIRS. Im EEG konnte nur die mPINV-Potentialkomponente ausgewertet werden, die iMP-Komponente konnte aufgrund technischer Probleme nicht ausgewertet werden. Die EMG-Messung fiel wie erwartet aus und zeigte für alle Bedingungen signifikante Aktivierung der ipsilateralen Muskulatur.
DISKUSSION Unsere Ergebnisse stehen nicht im Einklang mit der aktuellen Literatur. Teilweise stimmen sie mit der Arbeit von Romanos et al. (2007) aus unserer Arbeitsgruppe überein. Zudem ist zu erwähnen, dass bisher wenige Arbeiten existieren, die sich mit fNIRS-Messungen im Motorkortex beschäftigt haben. Zahlreiche Arbeiten dagegen beschäftigten sich mit der Inhibitionsleistung bei Patienten mit ADHS und zeigen dazu häufig Ergebnisse aus dem präfrontalen Kortex. Hierbei finden sich unterschiedliche Ergebnisse, die sowohl eine Hypo- als auch eine Hyperaktivität nachweisen können. Verschiedene Studien konnten zeigen, dass die Gehirnaktivität durch Methylphenidat normalisiert wird. Wir finden jedoch im – bisher schlecht untersuchten – Motorkortex eine diffusere Aktivierung durch die Medikation. Eine Studie von Lange et al. (2007) zeigte, dass durch MPH die Handschrift langsamer, aber ordentlicher wird. Möglicherweise wird durch die Medikation aus dem automatisierten Prozess des Schreibens ein bewusst kognitiv gesteuerter Prozess, der mit einer veränderten, verstärkten Gehirnaktivierung im Bereich des Motorkortex einhergeht. Dies könnte unseren Befund erklären. MPH wirkt im Bereich des dopaminergen Systems durch Bindung an den Dopamintransporter (K. H. Krause et al., 2000b). Eine besonders hohe Konzentration findet sich im Bereich des Striatums. Wir interpretieren unser Ergebnis so, dass eine Beeinflussung der subkortikalen Strukturen sekundär zu Aktivierungsveränderungen im Bereich des Motorkortex führt und so die diffusere Aktivierung erklärbar ist. Weitere Studien werden nötig sein um dieses Phänomen genauer zu untersuchen. Darüber hinaus zeigte sich, dass die Finger-Daumen-Oppositions-Aufgabe veränderte Gehirnpotentiale im Vergleich zur Tapping-Aufgabe hervorrief, vermutlich durch die erhöhte Komplexität bei der Finger-Daumen-Opposition.
Wir korrelierten die durch fNIRS und EEG gefundenen Aktivierungen und konnten keine aussagekräftige Korrelation finden, anders als in Studien von Ehlis et al. (2009) und Takeuchi et al. (2009).
Wie bereits mehrfach in anderen Studien beschrieben (Falkenstein et al., 1991; Gehring et al., 1993; Holroyd & Coles, 2002) konnte ein signifikanter Unterschied im EEG nach richtigen Antworten im Vergleich zu Fehlern in einem Zeitfenster von -35 bis 108 ms und von 110 bis 450 ms gezeigt werden. Die als Differenz aus den negativsten beziehungsweise positivsten Peaks nach falschen und richtigen Antworten berechnete „error-related negativity“ (ERN) und „error positivity“ (Pe) als wichtigste Komponenten der Fehlerverarbeitung zeigten im Vergleich zu anderen Studien zwar geringere, aber trotzdem vergleichbare Werte. Um den Einfluss von genetischen Unterschieden auf die Fehlerverarbeitung deutlich zu machen, wurde in dieser Studie untersucht, inwieweit Polymorphismen des Dopamintransporters (DAT), der Catechol-O-Methyl-Transferase (COMT) und des Phosphoproteins Stathmin Einfluss auf die Ausprägung der ERN und der Pe nehmen. Bezüglich des DAT-Polymorphismus konnte ein signifikanter Einfluss weder auf die ERN noch auf die Pe nachgewiesen werden. Hier ist zu vermuten, dass der Polymorphismus den Dopaminhaushalt der Basalganglien nicht nennenswert beeinträchtigt und demnach keinen Einfluss auf die Fehlerverarbeitung hat. Im Hinblick auf den COMT – Polymorphismus zeigte sich zwar kein Effekt auf die ERN, bei der Pe konnte man allerdings signifikante Unterschiede zwischen den Gruppen feststellen. Hier zeigten die homozygoten Träger des „val“ – Allels signifikant höhere Pe – Amplituden als die homozygoten Träger des „met“ – Allels. Heterozygote Personen lagen hinsichtlich der Pe – Amplitude zwischen den beiden anderen Gruppen. Dieser Effekt entspricht zwar nicht den Ergebnissen von anderen Studien (Egan et al., 2005; Frank et al., 2007), sollte aber dennoch Gegenstand weiterführender Forschung sein. Der Polymorphismus im Gen des Phosphoproteins Stathmin beeinflusste zwar die Amplitude der Pe nicht, zeigte aber signifikante Auswirkungen auf die ERN, wobei hier Träger des T-Allels signifikant kleinere ERN-Amplituden aufwiesen als Probanden, die dieses Allel nicht trugen. Allerdings wurde deutlich, dass dieser Effekt nach genauerer Analyse nicht stabil gegenüber Veränderungen war. Trotzdem ist davon auszugehen, dass dieser Polymorphismus die Funktion des ACC und damit auch die Fehlerverarbeitung beeinflusst, wodurch die Notwendigkeit weiterer Untersuchungen auf dem Gebiet des Phosphoproteins Stathmin gegeben ist.
Previous EEG research only investigated one stage ultimatum games (UGs). We investigated the influence of a second bargaining stage in an UG concerning behavioral responses, electro-cortical correlates and their moderations by the traits altruism, anger, anxiety, and greed in 92 participants. We found that an additional stage led to more rejection in the 2-stage UG (2SUG) and that increasing offers in the second stage compared to the first stage led to more acceptance. The FRN during a trial was linked to expectance evaluation concerning the fairness of the offers, while midfrontal theta was a marker for the needed cognitive control to overcome the respective default behavioral pattern. The FRN responses to unfair offers were more negative for either low or high altruism in the UG, while high trait anxiety led to more negative FRN responses in the first stage of 2SUG, indicating higher sensitivity to unfairness. Accordingly, the mean FRN response, representing the trait-like general electrocortical reactivity to unfairness, predicted rejection in the first stage of 2SUG. Additionally, we found that high trait anger led to more rejections for unfair offer in 2SUG in general, while trait altruism led to more rejection of unimproving unfair offers in the second stage of 2SUG. In contrast, trait anxiety led to more acceptance in the second stage of 2SUG, while trait greed even led to more acceptance if the offer was worse than in the stage before. These findings suggest, that 2SUG creates a trait activation situation compared to the UG.
Background: Since the replication crisis, standardization has become even more important in psychological science and neuroscience. As a result, many methods are being reconsidered, and researchers’ degrees of freedom in these methods are being discussed as a potential source of inconsistencies across studies.
New Method: With the aim of addressing these subjectivity issues, we have been working on a tutorial-like EEG (pre-)processing pipeline to achieve an automated method based on the semi-automated analysis proposed by Delorme and Makeig.
Results: Two scripts are presented and explained step-by-step to perform basic, informed ERP and frequency-domain analyses, including data export to statistical programs and visual representations of the data. The open-source software EEGlab in MATLAB is used as the data handling platform, but scripts based on code provided by Mike Cohen (2014) are also included.
Comparison with existing methods: This accompanying tutorial-like article explains and shows how the processing of our automated pipeline affects the data and addresses, especially beginners in EEG-analysis, as other (pre)-processing chains are mostly targeting rather informed users in specialized areas or only parts of a complete procedure. In this context, we compared our pipeline with a selection of existing approaches.
Conclusion: The need for standardization and replication is evident, yet it is equally important to control the plausibility of the suggested solution by data exploration. Here, we provide the community with a tool to enhance the understanding and capability of EEG-analysis. We aim to contribute to comprehensive and reliable analyses for neuro-scientific research.
We investigated the influence of mental imagery expertise in 15 pen and paper role-players as an expert group compared to the gender-matched control group of computer role-players in the difficult Vandenberg and Kuse mental rotation task. In this task, the participants have to decide which two of four rotated figures match the target figure. The dependent measures were performance speed and accuracy. In our exploratory investigation, we further examined midline frontal theta band activation, parietal alpha band activation, and parietal alpha band asymmetry in EEG as indicator for the chosen rotation strategy. Additionally, we explored the gender influence on performance and EEG activation, although a very small female sample section was given. The expected gender difference concerning performance accuracy was negated by expertise in pen and paper role-playing women, while the gender-specific difference in performance speed was preserved. Moreover, gender differences concerning electro-cortical measures revealed differences in rotation strategy, with women using top-down strategies compared to men, who were using top-down strategies and active inhibition of associative cortical areas. These strategy uses were further moderated by expertise, with higher expertise leading to more pronounced activation patters, especially during successful performance. However, due to the very limited sample size, the findings of this explorative study have to be interpreted cautiously.