TY  - THES
A1  - Patzwald, Christiane
T1  - Actions through the lens of communicative cues
BT  - the influence of verbal cues and emotional cues on action processing and action selection in the second year of life
N2  - The PhD thesis entitled “Actions through the lens of communicative cues. The influence of verbal cues and emotional cues on action processing and action selection in the second year of life” is based on four studies, which examined the cognitive integration of another person’s communicative cues (i.e., verbal cues, emotional cues) with behavioral cues in 18- and 24-month-olds. In the context of social learning of instrumental actions, it was investigated how the intention-related coherence of either a verbally announced action intention or an emotionally signaled action evaluation with an action demonstration influenced infants’ neuro-cognitive processing (Study I) and selection (Studies II, III, IV) of a novel object-directed action. Developmental research has shown that infants benefit from another’s behavioral cues (e.g., action effect, persistency, selectivity) to infer the underlying goal or intention, respectively, of an observed action (e.g., Cannon & Woodward, 2012; Woodward, 1998). Particularly action effects support infants in distinguishing perceptual action features (e.g., target object identity, movement trajectory, final target object state) from conceptual action features such as goals and intentions. However, less is known about infants’ ability to cognitively integrate another’s behavioral cues with additional action-related communicative cues. There is some evidence showing that in the second year of life, infants selectively imitate a novel action that is verbally (“There!”) or emotionally (positive expression) marked as aligning with the model’s action intention over an action that is verbally (“Whoops!”) or emotionally (negative expression) marked as unintentional (Carpenter, Akhtar, & Tomasello, 1998; Olineck & Poulin-Dubois, 2005, 2009; Repacholi, 2009; Repacholi, Meltzoff, Toub, & Ruba, 2016). Yet, it is currently unclear which role the specific intention-related coherence of a communicative cue with a behavioral cue plays in infants’ action processing and action selection that is, whether the communicative cue confirms, contrasts, clarifies, or is unrelated to the behavioral cue. Notably, by using both verbal cues and emotional cues, we examined not only two domains of communicative cues but also two qualitatively distinct relations between behavioral cues on the one hand and communicative cues on the other hand. More specifically, a verbal cue has the potential to communicate an action intention in the absence of an action demonstration and thus a prior-intention (Searle, 1983), whereas an emotional cue evaluates an ongoing or past action demonstration and thus signals an intention-in-action (Searle, 1983). In a first research focus, this thesis examined infants’ capacity to cognitively integrate another’s intention-related communicative cues and behavioral cues, and also focused on the role of the social cues’ coherence in infants’ action processing and action selection. In a second research focus, and to gain more elaborate insights into how the sub-processes of social learning (attention, encoding, response; cf. Bandura, 1977) are involved in this coherence-sensitive integrative processing, we employed a multi-measures approach. More specifically, we used Electroencephalography (EEG) and looking times to examine how the cues’ coherence influenced the compound of attention and encoding, and imitation (including latencies to first-touch and first-action) to address the compound of encoding and response. Based on the action-reconstruction account (Csibra, 2007), we predicted that infants use extra-motor information (i.e., communicative cues) together with behavioral cues to reconstruct another’s action intention. Accordingly, we expected infants to possess a flexibly organized internal action hierarchy, which they adapt according to the cues’ coherence that is, according to what they inferred to be the overarching action goal. More specifically, in a social-learning situation that comprised an adult model, who demonstrated an action on a novel object that offered two actions, we expected the demonstrated action to lead infants’ action hierarchy when the communicative (i.e., verbal, emotional) cue conveyed similar (confirming coherence) or no additional (un-related coherence) intention-related information relative to the behavioral cue. In terms of action selection, this action hierarchy should become evident in a selective imitation of the demonstrated action. However, when the communicative cue questioned (contrasting coherence) the behaviorally implied action goal or was the only cue conveying meaningful intention-related information (clarifying coherence), the verbally/emotionally intended action should ascend infants’ action hierarchy. Consequently, infants’ action selection should align with the verbally/emotionally intended action (goal emulation). Notably, these predictions oppose the direct-matching perspective (Rizzolatti & Craighero, 2004), according to which the observation of another’s action directly resonates with the observer’s motor repertoire, with this motor resonance enabling the identification of the underlying action goal. Importantly, the direct-matching perspective predicts a rather inflexible action hierarchy inasmuch as the process of goal identification should solely rely on the behavioral cue, irrespective of the behavioral cue’s coherence with extra-motor intention-related information, as it may be conveyed via communicative cues. As to the role of verbal cues, Study I used EEG to examine the influence of a confirming (Congruent) versus contrasting (Incongruent) coherence of a verbal action intention with the same action demonstration on 18-month-olds’ conceptual action processing (as measured via mid-latency mean negative ERP amplitude) and motor activation (as measured via central mu-frequency band power). The action was demonstrated on a novel object that offered two action alternatives from a neutral position. We expected mid-latency ERP negativity to be enhanced in Incongruent compared to Congruent, because past EEG research has demonstrated enhanced conceptual processing for stimuli that mismatched rather than matched the semantic context (Friedrich & Friederici, 2010; Kaduk et al., 2016). Regarding motor activation, Csibra (2007) posited that the identification of a clear action goal constitutes a crucial basis for motor activation to occur. We therefore predicted reduced mu power (indicating enhanced motor activation) for Congruent than Incongruent, because in Congruent, the cues’ match provides unequivocal information about the model’s action goal, whereas in Incongruent, the conflict may render the model’s action goal more unclear. Unexpectedly, in the entire sample, 18-month-olds’ mid-latency ERP negativity during the observation of the same action demonstration did not differ significantly depending on whether this action was congruent or incongruent with the model’s verbal action intention. Yet, post hoc analyses revealed the presence of two subgroups of infants, each of which exhibited significantly different mid-latency ERP negativity for Congruent versus Incongruent, but in opposing directions. The subgroups differed in their productive action-related language skills, with the linguistically more advanced infants exhibiting the expected response pattern of enhanced ERP mean negativity in Incongruent than Congruent, indicating enhanced conceptual processing of an action demonstration that was contrasted rather than confirmed by the verbal action context. As expected, central mu power in the entire sample was reduced in Congruent relative to Incongruent, indicating enhanced motor activation when the action demonstration was preceded by a confirming relative to a contrasting verbal action intention. This finding may indicate the covert preparation for a preferential imitation of the congruent relative to the incongruent action (Filippi et al., 2016; Frey & Gerry, 2006). Overall, these findings are in line with the action-reconstruction account (Csibra, 2007), because they suggest a coherence-sensitive attention to and encoding of the same perceptual features of another’s behavior and thus a cognitive integration of intention-related verbal cues and behavioral cues. Yet, because the subgroup constellation in infants’ ERPs was only discovered post hoc, future research is clearly required to substantiate this finding. Also, future research should validate our interpretation that enhanced motor activation may reflect an electrophysiological marker of subsequent imitation by employing EEG and imitation in a within-subjects design. Study II built on Study I by investigating the impact of coherence of a verbal cue and a behavioral cue on 18- and 24-month-olds’ action selection in an imitation study. When infants of both age groups observed a confirming (Congruent) or unrelated (Pseudo-word: action demonstration was associated with novel verb-like cue) coherence, they selectively imitated the demonstrated action over the not demonstrated, alternative action, with no difference between these two conditions. These findings suggest that, as expected, infants’ action hierarchy was led by the demonstrated action when the verbal cue provided similar (Congruent) or no additional (Pseudo-word) intention-related information relative to a meaningful behavioral cue. These findings support the above-mentioned interpretation that enhanced motor activation during action observation may reflect a covert preparation for imitation (Study I). Interestingly, infants did not seem to benefit from the intention-highlighting effect of the verbal cue in Congruent, suggesting that the verbal cue had an unspecific (e.g., attention-guiding) effect on infants’ action selection. Contrary, when infants observed a contrasting (Incongruent) or clarifying (Failed-attempt: model failed to manipulate the object but verbally announced a certain action intention) coherence, their action selection varied with age and also varied across the course of the experiment (block 1 vs. block 2). More specifically, the 24-month-olds made stronger use of the verbal cue for their action selection in block 1 than did the 18-month-olds. However, while the 18-month-olds’ use of the verbal cue increased across blocks, particularly in Incongruent, the 24-month-olds’ use of the verbal cue decreased across blocks. Overall, these results suggest that, as expected, infants’ action hierarchy in Incongruent (both age groups) and Failed-attempt (only 24-month-olds) drew on the verbal action intention, because in both age groups, infants emulated the verbal intention about as often as they imitated the demonstrated action or even emulated the verbal action intention preferentially. Yet, these findings were confined to certain blocks. It may be argued that the younger age group had a harder time inferring and emulating the intended, yet never observed action, because this requirement is more demanding in cognitive and motor terms. These demands may explain why the 18-month-olds needed some time to take account of the verbal action intention. Contrary, it seems that the 24-month-olds, although demonstrating their principle capacity to take account of the verbal cue in block 1, lost trust in the model’s verbal cue, maybe because the verbal cue did not have predictive value for the model’s actual behavior. Supporting this interpretation, research on selective trust has demonstrated that already infants evaluate another’s reliability or competence, respectively, based on how that model handles familiar objects (behavioral reliability) or labels familiar objects (verbal reliability; for reviews, see Mills, 2013; Poulin-Dubois & Brosseau-Liard, 2016). Relatedly, imitation research has demonstrated that the interpersonal aspects of a social-learning situation gain increasing relevance for infants during the second year of life (Gellén & Buttelmann, 2019; Matheson, Moore, & Akhtar, 2013; Uzgiris, 1981). It may thus be argued that when the 24-month-olds were repeatedly faced with a verbally unreliable model, they de-evaluated the verbal cue as signaling the model’s action intention and instead relied more heavily on alternative cues such as the behavioral cue (Incongruent) or the action context (e.g., object affordances, salience; Failed-attempt). Infants’ first-action latencies were higher in Incongruent and Failed-attempt than in both Congruent and Pseudo-word, and were also higher in Failed-attempt than in Incongruent. These latency-findings thus indicate that situations involving a meaningful verbal cue that deviated from the behavioral cue are cognitively more demanding, resulting in a delayed initiation of a behavioral response. In sum, the findings of Study II suggest that both age groups were highly flexible in their integration of a verbal cue and behavioral cue. Moreover, our results do not indicate a general superiority of either cue. Instead, it seems to depend on the informational gain conveyed by the verbal cue whether it exerts a specific, intention-highlighting effect (Incongruent, Failed-attempt) or an unspecific (e.g., attention-guiding) effect (Congruent, Pseudo-word). Studies III and IV investigated the impact of another’s action-related emotional cues on 18-month-olds’ action selection. In Study III, infants observed a model, who demonstrated two actions on a novel object in direct succession, and who combined one of the two actions with a positive (happy) emotional expression and the other action with a negative (sad) emotional expression. As expected, infants imitated the positively emoted (PE) action more often than the negatively emoted (NE) action. This preference arose from an increase in infants’ readiness to perform the PE action from the baseline period (prior to the action demonstrations) to the test period (following the action demonstrations), rather than from a decrease in readiness to the perform the NE action. The positive cue thus had a stronger behavior-regulating effect than the negative cue. Notably, infants’ more general object-directed behavior in terms of first-touch latencies remained unaffected by the emotional cues’ valence, indicating that infants had linked the emotional cues specifically to the corresponding action and not the object as a whole (Repacholi, 2009). Also, infants’ looking times during the action demonstration did not differ significantly as a function of emotional valence and were characterized by a predominant attentional focus to the action/object rather than to the model’s face. Together with the findings on infants’ first-touch latencies, these results indicate a sensitivity for the notion that emotions can have very specific referents (referential specificity; Martin, Maza, McGrath, & Phelps, 2014). Together, Study III provided evidence for selective imitation based on another’s intention-related (particularly positive) emotional cues in an action-selection task, and thus indicates that infants’ action hierarchy flexibly responds to another’s emotional evaluation of observed actions. According to Repacholi (2009), we suggest that infants used the model’s emotional evaluation to re-appraise the corresponding action (effect), for instance in terms of desirability. Study IV followed up on Study III by investigating the role of the negative emotional cue for infants’ action selection in more detail. Specifically, we investigated whether a contrasting (negative) emotional cue alone would be sufficient to differentially rank the two actions along infants’ action hierarchy or whether instead infants require direct information about the model’s action intention (in the form of a confirming action-emotion pair) to align their action selection with the emotional cues. Also, we examined whether the absence of a direct behavior-regulating effect of the negative cue in Study III was due to the negative cue itself or to the concurrently available positive cue masking the negative cue’s potential effect. To this end, we split the demonstration of the two action-emotion pairs across two trials. In each trial, one action was thus demonstrated and emoted (PE, NE action), and one action was not demonstrated and un-emoted (UE action). For trial 1, we predicted that infants, who observed a PE action demonstration, would selectively imitate the PE action, whereas infants, who observed a NE action demonstration would selectively emulate the UE action. As to trial 2, we expected the complementary action-emotion pair to provide additional clarifying information as the model’s emotional evaluation of both actions, which should either lead to adaptive perseveration (if infants’ action selection in trial 1 had already drawn on the emotional cue) or adaptive change (if infants’ action selection in trial 1 signaled a disregard of the emotional cue). As to trial 1, our findings revealed that, as expected, infants imitated the PE action more often than they emulated the UE action. Like in Study III, this selectivity arose from an increase in infants’ propensity to perform the PE action from baseline to trial 1. Also like in Study III, infants performed the NE action about equally often in baseline and trial 1, which speaks against a direct behavior-regulating effect of the negative cue also when presented in isolation. However, after a NE action demonstration, infants emulated the UE action more often in trial 1 than in baseline, suggesting an indirect behavior-regulating effect of the negative cue. Yet, this indirect effect did not yield a selective emulation of the UE action, because infants performed both action alternatives about equally often in trial 1. Unexpectedly, infants’ action selection in trial 2 was unaffected by the emotional cue. Instead, infants perseverated their action selection of trial 1 in trial 2, irrespective of whether it was adaptive or non-adaptive with respect to the model’s emotional evaluation of the action. It seems that infants changed their strategy across trials, from an initial adherence to the emotional (particularly positive) cue, towards bringing about a salient action effect (Marcovich & Zelazo, 2009). In sum, Studies III and IV indicate a dynamic interplay of different action-selection strategies, depending on valence and presentation order. Apparently, at least in infancy, action reconstruction as one basis for selective action performance reaches its limits when infants can only draw on indirect intention-related information (i.e., which action should be avoided). Overall, our findings favor the action-reconstruction account (Csibra, 2007), according to which actions are flexibly organized along a hierarchy, depending on inferential processes based on extra-motor intention-related information. At the same time, the findings question the direct-matching hypothesis (Rizzolatti & Craighero, 2004), according to which the identification (and pursuit) of action goals hinges on a direct simulation of another’s behavioral cues. Based on the studies’ findings, a preliminary working model is introduced, which seeks to integrate the two theoretical accounts by conceptualizing the routes that activation induced by social cues may take to eventually influence an infant’s action selection. Our findings indicate that it is useful to strive a differentiated conceptualization of communicative cues, because they seem to operate at different places within the process of cue integration, depending on their potential to convey direct intention-related information. Moreover, we suggest that there is bidirectional exchange within each compound of adjacent sub-processes (i.e., between attention and encoding, and encoding and response), and between the compounds. Hence, our findings highlight the benefits of a multi-measures approach when studying the development of infants’ social-cognitive abilities, because it provides a more comprehensive picture how the concerted use of social cues from different domains influences infants’ processing and selection of instrumental actions. Finally, this thesis points to potential future directions to substantiate our current interpretation of the findings.. Moreover, an extension to additional kinds of coherence is suggested to get closer to infants’ everyday-world of experience.
KW  - infancy
KW  - social cognition
KW  - action processing
KW  - emotions
KW  - language
KW  - imitation
KW  - EEG
Y1  - 2020
ER  - 
TY  - JOUR
A1  - Gebel, Arnd
A1  - Lehmann, Tim
A1  - Granacher, Urs
T1  - Balance task difficulty affects postural sway and cortical activity in healthy adolescents
JF  - Experimental brain research
N2  - Electroencephalographic (EEG) research indicates changes in adults' low frequency bands of frontoparietal brain areas executing different balance tasks with increasing postural demands. However, this issue is unsolved for adolescents when performing the same balance task with increasing difficulty. Therefore, we examined the effects of a progressively increasing balance task difficulty on balance performance and brain activity in adolescents. Thirteen healthy adolescents aged 16-17 year performed tests in bipedal upright stance on a balance board with six progressively increasing levels of task difficulty. Postural sway and cortical activity were recorded simultaneously using a pressure sensitive measuring system and EEG. The power spectrum was analyzed for theta (4-7 Hz) and alpha-2 (10-12 Hz) frequency bands in pre-defined frontal, central, and parietal clusters of electrocortical sources. Repeated measures analysis of variance (rmANOVA) showed a significant main effect of task difficulty for postural sway (p < 0.001; d = 6.36). Concomitantly, the power spectrum changed in frontal, bilateral central, and bilateral parietal clusters. RmANOVAs revealed significant main effects of task difficulty for theta band power in the frontal (p < 0.001, d = 1.80) and both central clusters (left: p < 0.001, d = 1.49; right: p < 0.001, d = 1.42) as well as for alpha-2 band power in both parietal clusters (left: p < 0.001, d = 1.39; right: p < 0.001, d = 1.05) and in the central right cluster (p = 0.005, d = 0.92). Increases in theta band power (frontal, central) and decreases in alpha-2 power (central, parietal) with increasing balance task difficulty may reflect increased attentional processes and/or error monitoring as well as increased sensory information processing due to increasing postural demands. In general, our findings are mostly in agreement with studies conducted in adults. Similar to adult studies, our data with adolescents indicated the involvement of frontoparietal brain areas in the regulation of postural control. In addition, we detected that activity of selected brain areas (e.g., bilateral central) changed with increasing postural demands.
KW  - balance
KW  - postural control
KW  - EEG
KW  - Theta
KW  - Alpha-2
KW  - ICA
KW  - youth
Y1  - 2020
U6  - https://doi.org/10.1007/s00221-020-05810-1
SN  - 0014-4819
SN  - 1432-1106
VL  - 238
IS  - 5
SP  - 1323
EP  - 1333
PB  - Springer
CY  - New York
ER  - 
TY  - THES
A1  - Ziehe, Andreas
T1  - Blind source separation based on joint diagonalization of matrices with applications in biomedical signal processing
T1  - Blinde Signalquellentrennung beruhend auf simultaner Diagonalisierung von Matrizen mit Anwendungen in der biomedizinischen Signalverarbeitung
T1  - Blinde Signalquellentrennung beruhend auf simultaner Diagonalisierung von Matrizen mit Anwendungen in der biomedizinischen Signalverarbeitung
N2  - This thesis is concerned with the solution of the blind source separation problem (BSS). The BSS problem occurs frequently in various scientific and technical applications. In essence, it consists in separating meaningful underlying components out of a mixture of a multitude of superimposed signals.  In the recent research literature there are two related approaches to the BSS problem: The first is known as Independent Component Analysis (ICA), where the goal is to transform the data such that the components become as independent as possible. The second is based on the notion of diagonality of certain characteristic matrices derived from the data. Here the goal is to transform the matrices such that they become as diagonal as possible. In this thesis we study the latter method of approximate joint diagonalization (AJD) to achieve a solution of the BSS problem. After an introduction to the general setting, the thesis provides an overview on particular choices for the set of target matrices that can be used for BSS by joint diagonalization.  As the main contribution of the thesis, new algorithms for approximate joint diagonalization of several matrices with non-orthogonal transformations are developed.  These newly developed algorithms will be tested on synthetic benchmark datasets and compared to other previous diagonalization algorithms.  Applications of the BSS methods to biomedical signal processing are discussed and exemplified with real-life data sets of multi-channel biomagnetic recordings.
N2  - Diese Arbeit befasst sich mit der Lösung des Problems der blinden Signalquellentrennung (BSS). Das BSS Problem tritt häufig in vielen wissenschaftlichen und technischen Anwendungen auf. Im Kern besteht das Problem darin, aus einem Gemisch von überlagerten Signalen die zugrundeliegenden Quellsignale zu extrahieren.  In wissenschaftlichen Publikationen zu diesem Thema werden hauptsächlich zwei Lösungsansätze verfolgt:  Ein Ansatz ist die sogenannte "Analyse der unabhängigen Komponenten", die zum Ziel hat, eine lineare Transformation <B>V</B> der Daten <B>X</B> zu finden, sodass die Komponenten Un der transformierten Daten <B>U</B> = <B> V X</B> (die sogenannten "independent components") so unabhängig wie möglich sind. Ein anderer Ansatz beruht auf einer simultanen Diagonalisierung mehrerer spezieller Matrizen, die aus den Daten gebildet werden. Diese Möglichkeit der Lösung des Problems der blinden Signalquellentrennung bildet den Schwerpunkt dieser Arbeit.  Als Hauptbeitrag der vorliegenden Arbeit präsentieren wir neue Algorithmen zur simultanen Diagonalisierung mehrerer Matrizen mit Hilfe einer nicht-orthogonalen Transformation.  Die neu entwickelten Algorithmen werden anhand von numerischen Simulationen getestet und mit bereits bestehenden Diagonalisierungsalgorithmen verglichen. Es zeigt sich, dass unser neues Verfahren sehr effizient und leistungsfähig ist. Schließlich werden Anwendungen der BSS Methoden auf Probleme der biomedizinischen Signalverarbeitung erläutert und anhand von realistischen biomagnetischen Messdaten wird die Nützlichkeit in der explorativen Datenanalyse unter Beweis gestellt.
KW  - Signaltrennung
KW  - Mischung <Signalverarbeitung>
KW  - Diagonalisierung
KW  - Bioelektrisches Signal
KW  - Magnetoencephalographie
KW  - Elektroencephalographie
KW  - Signalquellentrennung
KW  - Matrizen-Eigenwertaufgabe
KW  - Simultane Diagonalisierung
KW  - Optimierungsproblem
KW  - blind source separation
KW  - BSS
KW  - ICA
KW  - independent component analysis
KW  - approximate joint diagonalization
KW  - EEG
KW  - MEG
Y1  - 2005
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5694
ER  - 
TY  - BOOK
A1  - Dambacher, Michael
T1  - Bottom-up and top-down processes in reading : influences of frequency and predictability on event-related potentials and eye movements
N2  - In reading, word frequency is commonly regarded as the major bottom-up determinant for the speed of lexical access. Moreover, language processing depends on top-down information, such as the predictability of a word from a previous context. Yet, however, the exact role of top-down predictions in visual word recognition is poorly understood: They may rapidly affect lexical processes, or alternatively, influence only late post-lexical stages. To add evidence about the nature of top-down processes and their relation to bottom-up information in the timeline of word recognition, we examined influences of frequency and predictability on event-related potentials (ERPs) in several sentence reading studies. The results were related to eye movements from natural reading as well as to models of word recognition. As a first and major finding, interactions of frequency and predictability on ERP amplitudes consistently revealed top-down influences on lexical levels of word processing (Chapters 2 and 4). Second, frequency and predictability mediated relations between N400 amplitudes and fixation durations, pointing to their sensitivity to a common stage of word recognition; further, larger N400 amplitudes entailed longer fixation durations on the next word, a result providing evidence for ongoing processing beyond a fixation (Chapter 3). Third, influences of presentation rate on ERP frequency and predictability effects demonstrated that the time available for word processing critically co-determines the course of bottom-up and top-down influences (Chapter 4). Fourth, at a near-normal reading speed, an early predictability effect suggested the rapid comparison of top-down hypotheses with the actual visual input (Chapter 5). The present results are compatible with interactive models of word recognition assuming that early lexical processes depend on the concerted impact of bottom-up and top-down information. We offered a framework that reconciles the findings on a timeline of word recognition taking into account influences of frequency, predictability, and presentation rate (Chapter 4).
N2  - Wortfrequenz wird in der Leseforschung als wesentliche Bottom-up Determinante für die Geschwindigkeit des lexikalischen Zugriffs betrachtet. Darüber hinaus spielen Top-down Informationen, wie die kontextbasierte Wortvorhersagbarkeit, in der Sprachverarbeitung eine wichtige Rolle. Bislang ist die exakte Bedeutung von Top-down Vorhersagen in der visuellen Worterkennung jedoch unzureichend verstanden: Es herrscht Uneinigkeit darüber, ob ausschließlich späte post-lexikalische, oder auch frühe lexikalische Verarbeitungsstufen durch Vorhersagbarkeit beeinflusst werden. Um ein besseres Verständnis von Top-down Prozessen und deren Zusammenhänge mit Bottom-up Informationen in der Worterkennung zu gewährleisten, wurden in der vorliegenden Arbeit Einflüsse von Frequenz und Vorhersagbarkeit auf ereigniskorrelierte Potentiale (EKPs) untersucht. Die Ergebnisse aus mehreren Satzlesestudien wurden mit Blickbewegungen beim natürlichen Lesen sowie mit Modellen der Worterkennung in Beziehung gesetzt. Als primärer Befund zeigten sich in EKP Amplituden konsistent Interaktionen zwischen Frequenz und Vorhersagbarkeit. Die Ergebnisse deuten auf Top-down Einflüsse während lexikalischer Wortverarbeitungsstufen hin (Kapitel 2 und 4). Zweitens mediierten Frequenz und Vorhersagbarkeit Zusammenhänge zwischen N400 Amplituden und Fixationsdauern; die Modulation beider abhängigen Maße lässt auf eine gemeinsame Wortverarbeitungsstufe schließen. Desweiteren signalisierten längere Fixationsdauern nach erhöhten N400 Amplituden das Andauern der Wortverarbeitung über die Dauer einer Fixation hinaus (Kapitel 3). Drittens zeigten sich Einflüsse der Präsentationsrate auf Frequenz- und Vorhersagbarkeitseffekte in EKPs. Der Verlauf von Bottom-up und Top-down Prozessen wird demnach entscheidend durch die zur Wortverarbeitung verfügbaren Zeit mitbestimmt (Kapitel 4). Viertens deutete ein früher Vorhersagbarkeitseffekt bei einer leseähnlichen Präsentationsgeschwindigkeit auf den schnellen Abgleich von Top-down Vorhersagen mit dem tatsächlichen visuellen Input hin (Kapitel 5). Die Ergebnisse sind mit interaktiven Modellen der Worterkennung vereinbar, nach welchen Bottom-up und Top-down Informationen gemeinsam frühe lexikalische Verarbeitungsstufen beeinflussen. Unter Berücksichtigung der Effekte von Frequenz, Vorhersagbarkeit und Präsentationsgeschwindigkeit wird ein Modell vorgeschlagen, das die vorliegenden Befunde zusammenführt (Kapitel 4).
T3  - Potsdam Cognitive Science Series - 1 
KW  - Lesen
KW  - visuelle Worterkennung
KW  - Bottom-up
KW  - Top-down
KW  - Frequenz
KW  - Vorhersagbarkeit
KW  - Stimulus-Onset Asynchrony
KW  - EEG
KW  - ereigniskorrelierte Potentiale
KW  - reading
KW  - visual word recognition
KW  - bottom-up
KW  - top-down
KW  - frequency
KW  - predictability
KW  - stimulus-onset asynchrony
KW  - EEG
KW  - event-related potentials
Y1  - 2010
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-42024
SN  - 978-3-86956-059-5
PB  - Universitätsverlag Potsdam
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Dornhege, Guido
A1  - Blankertz, Benjamin
A1  - Krauledat, Matthias
A1  - Losch, Florian
A1  - Curio, Gabriel
A1  - Müller, Klaus-Robert
T1  - Combined optimization of spatial and temporal filters for improving brain-computer interfacing
JF  - IEEE transactions on bio-medical electronics
N2  - Brain-computer interface (BCI) systems create a novel communication channel from the brain to an output de ice by bypassing conventional motor output pathways of nerves and muscles. Therefore they could provide a new communication and control option for paralyzed patients. Modern BCI technology is essentially based on techniques for the classification of single-trial brain signals. Here we present a novel technique that allows the simultaneous optimization of a spatial and a spectral filter enhancing discriminability rates of multichannel EEG single-trials. The evaluation of 60 experiments involving 22 different subjects demonstrates the significant superiority of the proposed algorithm over to its classical counterpart: the median classification error rate was decreased by 11%. Apart from the enhanced classification, the spatial and/or the spectral filter that are determined by the algorithm can also be used for further analysis of the data, e.g., for source localization of the respective brain rhythms.
KW  - brain-computer interface
KW  - common spatial patterns
KW  - EEG
KW  - event-related desynchronization
KW  - single-trial-analysis
Y1  - 2006
U6  - https://doi.org/10.1109/TBME.2006.883649
SN  - 0018-9294
VL  - 53
IS  - 11
SP  - 2274
EP  - 2281
PB  - IEEE
CY  - New York
ER  - 
TY  - JOUR
A1  - Dimigen, Olaf
A1  - Sommer, Werner
A1  - Hohlfeld, Annette
A1  - Jacobs, Arthur M.
A1  - Kliegl, Reinhold
T1  - Coregistration of eye movements and EEG in natural reading analyses and review
JF  - Journal of experimental psychology : General
N2  - Brain-electric correlates of reading have traditionally been studied with word-by-word presentation, a condition that eliminates important aspects of the normal reading process and precludes direct comparisons between neural activity and oculomotor behavior. In the present study, we investigated effects of word predictability on eye movements (EM) and fixation-related brain potentials (FRPs) during natural sentence reading. Electroencephalogram (EEG) and EM (via video-based eye tracking) were recorded simultaneously while subjects read heterogeneous German sentences, moving their eyes freely over the text. FRPs were time-locked to first-pass reading fixations and analyzed according to the cloze probability of the currently fixated word. We replicated robust effects of word predictability on EMs and the N400 component in FRPs. The data were then used to model the relation among fixation duration, gaze duration, and N400 amplitude, and to trace the time course of EEG effects relative to effects in EM behavior. In an extended Methodological Discussion section, we review 4 technical and data-analytical problems that need to be addressed when FRPs are recorded in free-viewing situations (such as reading, visual search, or scene perception) and propose solutions. Results suggest that EEG recordings during normal vision are feasible and useful to consolidate findings from EEG and eye-tracking studies.
KW  - EEG
KW  - eye tracking
KW  - fixation-related potentials
KW  - artifact correction
KW  - natural viewing
Y1  - 2011
U6  - https://doi.org/10.1037/a0023885
SN  - 0096-3445
VL  - 140
IS  - 4
SP  - 552
EP  - 572
PB  - American Psychological Association
CY  - Washington
ER  - 
TY  - JOUR
A1  - McLoughlin, Grainne
A1  - Palmer, Jason
A1  - Makeig, Scott
A1  - Bigdely-Shamlo, Nima
A1  - Banaschewski, Tobias
A1  - Laucht, Manfred
A1  - Brandeis, D.
T1  - EEG Source Imaging Indices of Cognitive Control Show Associations with Dopamine System Genes
JF  - Brain Topography
N2  - Cognitive or executive control is a critical mental ability, an important marker of mental illness, and among the most heritable of neurocognitive traits. Two candidate genes, catechol-O-methyltransferase (COMT) and DRD4, which both have a roles in the regulation of cortical dopamine, have been consistently associated with cognitive control. Here, we predicted that individuals with the COMT Met/Met allele would show improved response execution and inhibition as indexed by event-related potentials in a Go/NoGo task, while individuals with the DRD4 7-repeat allele would show impaired brain activity. We used independent component analysis (ICA) to separate brain source processes contributing to high-density EEG scalp signals recorded during the task. As expected, individuals with the DRD4 7-repeat polymorphism had reduced parietal P3 source and scalp responses to response (Go) compared to those without the 7-repeat. Contrary to our expectation, the COMT homozygous Met allele was associated with a smaller frontal P3 source and scalp response to response-inhibition (NoGo) stimuli, suggesting that while more dopamine in frontal cortical areas has advantages in some tasks, it may also compromise response inhibition function. An interaction effect emerged for P3 source responses to Go stimuli. These were reduced in those with both the 7-repeat DRD4 allele and either the COMT Val/Val or the Met/Met homozygous polymorphisms but not in those with the heterozygous Val/Met polymorphism. This epistatic interaction between DRD4 and COMT replicates findings that too little or too much dopamine impairs cognitive control. The anatomic and functional separated maximally independent cortical EEG sources proved more informative than scalp channel measures for genetic studies of brain function and thus better elucidate the complex mechanisms in psychiatric illness.
KW  - EEG
KW  - Genetics
KW  - DRD4
KW  - COMT
KW  - ICA
KW  - Measure projection
Y1  - 2017
U6  - https://doi.org/10.1007/s10548-017-0601-z
SN  - 0896-0267
SN  - 1573-6792
VL  - 31
IS  - 3
SP  - 392
EP  - 406
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - GEN
A1  - Gebel, Arnd
A1  - Busch, Aglaja
A1  - Stelzel, Christine
A1  - Hortobágyi, Tibor
A1  - Granacher, Urs
T1  - Effects of Physical and Mental Fatigue on Postural Sway and Cortical Activity in Healthy Young Adults
T2  - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe
N2  - Physical fatigue (PF) negatively affects postural control, resulting in impaired balance performance in young and older adults. Similar effects on postural control can be observed for mental fatigue (MF) mainly in older adults. Controversial results exist for young adults. There is a void in the literature on the effects of fatigue on balance and cortical activity. Therefore, this study aimed to examine the acute effects of PF and MF on postural sway and cortical activity. Fifteen healthy young adults aged 28 ± 3 years participated in this study. MF and PF protocols comprising of an all-out repeated sit-to-stand task and a computer-based attention network test, respectively, were applied in random order. Pre and post fatigue, cortical activity and postural sway (i.e., center of pressure displacements [CoPd], velocity [CoPv], and CoP variability [CV CoPd, CV CoPv]) were tested during a challenging bipedal balance board task. Absolute spectral power was calculated for theta (4–7.5 Hz), alpha-2 (10.5–12.5 Hz), beta-1 (13–18 Hz), and beta-2 (18.5–25 Hz) in frontal, central, and parietal regions of interest (ROI) and baseline-normalized. Inference statistics revealed a significant time-by-fatigue interaction for CoPd (p = 0.009, d = 0.39, Δ 9.2%) and CoPv (p = 0.009, d = 0.36, Δ 9.2%), and a significant main effect of time for CoP variability (CV CoPd: p = 0.001, d = 0.84; CV CoPv: p = 0.05, d = 0.62). Post hoc analyses showed a significant increase in CoPd (p = 0.002, d = 1.03) and CoPv (p = 0.003, d = 1.03) following PF but not MF. For cortical activity, a significant time-by-fatigue interaction was found for relative alpha-2 power in parietal (p < 0.001, d = 0.06) areas. Post hoc tests indicated larger alpha-2 power increases after PF (p < 0.001, d = 1.69, Δ 3.9%) compared to MF (p = 0.001, d = 1.03, Δ 2.5%). In addition, changes in parietal alpha-2 power and measures of postural sway did not correlate significantly, irrespective of the applied fatigue protocol. No significant changes were found for the other frequency bands, irrespective of the fatigue protocol and ROI under investigation. Thus, the applied PF protocol resulted in increased postural sway (CoPd and CoPv) and CoP variability accompanied by enhanced alpha-2 power in the parietal ROI while MF led to increased CoP variability and alpha-2 power in our sample of young adults. Potential underlying cortical mechanisms responsible for the greater increase in parietal alpha-2 power after PF were discussed but could not be clearly identified as cause. Therefore, further future research is needed to decipher alternative interpretations.
T3  - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - 793 
KW  - balance
KW  - cognitive/muscular fatigue
KW  - EEG
KW  - theta
KW  - alpha-2
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-564419
SN  - 1866-8364
SP  - 1
EP  - 14
PB  - Universitätsverlag Potsdam
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Gebel, Arnd
A1  - Busch, Aglaja
A1  - Stelzel, Christine
A1  - Hortobágyi, Tibor
A1  - Granacher, Urs
T1  - Effects of Physical and Mental Fatigue on Postural Sway and Cortical Activity in Healthy Young Adults
JF  - Frontiers in Human Neuroscience
N2  - Physical fatigue (PF) negatively affects postural control, resulting in impaired balance performance in young and older adults. Similar effects on postural control can be observed for mental fatigue (MF) mainly in older adults. Controversial results exist for young adults. There is a void in the literature on the effects of fatigue on balance and cortical activity. Therefore, this study aimed to examine the acute effects of PF and MF on postural sway and cortical activity. Fifteen healthy young adults aged 28 ± 3 years participated in this study. MF and PF protocols comprising of an all-out repeated sit-to-stand task and a computer-based attention network test, respectively, were applied in random order. Pre and post fatigue, cortical activity and postural sway (i.e., center of pressure displacements [CoPd], velocity [CoPv], and CoP variability [CV CoPd, CV CoPv]) were tested during a challenging bipedal balance board task. Absolute spectral power was calculated for theta (4–7.5 Hz), alpha-2 (10.5–12.5 Hz), beta-1 (13–18 Hz), and beta-2 (18.5–25 Hz) in frontal, central, and parietal regions of interest (ROI) and baseline-normalized. Inference statistics revealed a significant time-by-fatigue interaction for CoPd (p = 0.009, d = 0.39, Δ 9.2%) and CoPv (p = 0.009, d = 0.36, Δ 9.2%), and a significant main effect of time for CoP variability (CV CoPd: p = 0.001, d = 0.84; CV CoPv: p = 0.05, d = 0.62). Post hoc analyses showed a significant increase in CoPd (p = 0.002, d = 1.03) and CoPv (p = 0.003, d = 1.03) following PF but not MF. For cortical activity, a significant time-by-fatigue interaction was found for relative alpha-2 power in parietal (p < 0.001, d = 0.06) areas. Post hoc tests indicated larger alpha-2 power increases after PF (p < 0.001, d = 1.69, Δ 3.9%) compared to MF (p = 0.001, d = 1.03, Δ 2.5%). In addition, changes in parietal alpha-2 power and measures of postural sway did not correlate significantly, irrespective of the applied fatigue protocol. No significant changes were found for the other frequency bands, irrespective of the fatigue protocol and ROI under investigation. Thus, the applied PF protocol resulted in increased postural sway (CoPd and CoPv) and CoP variability accompanied by enhanced alpha-2 power in the parietal ROI while MF led to increased CoP variability and alpha-2 power in our sample of young adults. Potential underlying cortical mechanisms responsible for the greater increase in parietal alpha-2 power after PF were discussed but could not be clearly identified as cause. Therefore, further future research is needed to decipher alternative interpretations.
KW  - balance
KW  - cognitive/muscular fatigue
KW  - EEG
KW  - theta
KW  - alpha-2
Y1  - 2022
U6  - https://doi.org/10.3389/fnhum.2022.871930
SN  - 1662-5161
VL  - 16
SP  - 1
EP  - 14
PB  - Frontiers Media S.A.
CY  - Lausanne, Schweiz
ER  - 
TY  - GEN
A1  - Ventura-Bort, Carlos
A1  - Wirkner, Janine
A1  - Genheimer, Hannah
A1  - Wendt, Julia
A1  - Hamm, Alfons O.
A1  - Weymar, Mathias
T1  - Effects of Transcutaneous Vagus Nerve Stimulation (tVNS) on the P300 and Alpha-Amylase Level
BT  - A Pilot Study
T2  - Postprints der Universität Potsdam : Humanwissenschaftliche Reihe
N2  - 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.
T3  - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - 473 
KW  - EEG
KW  - P300
KW  - tVNS
KW  - norepinephrine
KW  - locus coeruleus
KW  - salivary alpha-amylase
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-419259
IS  - 473
ER  -