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Fear conditioning is an efficient model of associative learning, which has greatly improved our knowledge of processes underlying the development and maintenance of pathological fear and anxiety. In a differential fear conditioning paradigm, one initially neutral stimulus (NS) is paired with an aversive event (unconditioned stimulus, US), whereas another stimulus does not have any consequences. After a few pairings the NS is associated with the US and consequently becomes a conditioned stimulus (CS+), which elicits a conditioned response (CR).
The formation of explicit knowledge of the CS/US association during conditioning is referred to as contingency awareness. Findings about its role in fear conditioning are ambiguous. The development of a CR without contingency awareness has been shown in delay fear conditioning studies. One speaks of delay conditioning, when the US coterminates with or follows directly on the CS+. In trace conditioning, a temporal gap or “trace interval” lies between CS+ and US. According to existing evidence, trace conditioning is not possible on an implicit level and requires more cognitive resources than delay conditioning.
The associations formed during fear conditioning are not exclusively associations between specific cues and aversive events. Contextual cues form the background milieu of the learning process and play an important role in both acquisition and the extinction of conditioned fear and anxiety. A common limitation in human fear conditioning studies is the lack of ecological validity, especially regarding contextual information. The use of Virtual Reality (VR) is a promising approach for creating a more complex environment which is close to a real life situation.
I conducted three studies to examine cue and contextual fear conditioning with regard to the role of contingency awareness. For this purpose a VR paradigm was created, which allowed for exact manipulation of cues and contexts as well as timing of events. In all three experiments, participants were guided through one or more virtual rooms serving as contexts, in which two different lights served as CS and an electric stimulus as US. Fear potentiated startle (FPS) responses were measured as an indicator of implicit fear conditioning. To test whether participants had developed explicit awareness of the CS-US contingencies, subjective ratings were collected.
The first study was designed as a pilot study to test the VR paradigm as well as the conditioning protocol. Additionally, I was interested in the effect of contingency awareness. Results provided evidence, that eye blink conditioning is possible in the virtual environment and that it does not depend on contingency awareness. Evaluative conditioning, as measured by subjective ratings, was only present in the group of participants who explicitly learned the association between CS and US.
To examine acquisition and extinction of both fear associated cues and contexts, a novel cue-context generalization paradigm was applied in the second study. Besides the interplay of cues and contexts I was again interested in the effect of contingency awareness. Two different virtual offices served as fear and safety context, respectively. During acquisition, the CS+ was always followed by the US in the fear context. In the safety context, none of the lights had any consequences. During extinction, a additional (novel) context was introduced, no US was delivered in any of the contexts. Participants showed enhanced startle responses to the CS+ compared to the CS- in the fear context. Thus, discriminative learning took place regarding both cues and contexts during acquisition. This was confirmed by subjective ratings, although only for participants with explicit contingency awareness. Generalization of fear to the novel context after conditioning did not depend on awareness and was observable only on trend level.
In a third experiment I looked at neuronal correlates involved in extinction of fear memory by means of functional magnetic resonance imaging (fMRI). Of particular interest were differences between extinction of delay and trace fear conditioning. I applied the paradigm tested in the pilot study and additionally manipulated timing of the stimuli: In the delay conditioning group (DCG) the US was administered with offset of one light (CS+), in the trace conditioning group (TCG) the US was presented 4s after CS+ offset. Most importantly, prefrontal activation differed between the two groups. In line with existing evidence, the ventromedial prefrontal cortex (vmPFC) was activated in the DCG. In the TCG I found activation of the dorsolateral prefrontal cortex (dlPFC), which might be associated with modulation of working memory processes necessary for bridging the trace interval and holding information in short term memory.
Taken together, virtual reality proved to be an elegant tool for examining human fear conditioning in complex environments, and especially for manipulating contextual information. Results indicate that explicit knowledge of contingencies is necessary for attitude formation in fear conditioning, but not for a CR on an implicit level as measured by FPS responses. They provide evidence for a two level account of fear conditioning. Discriminative learning was successful regarding both cues and contexts. Imaging results speak for different extinction processes in delay and trace conditioning, hinting that higher working memory contribution is required for trace than for delay conditioning.
Task instructions modulate the attentional mode affecting the auditory MMN and the semantic N400
(2014)
Event-related potentials (ERPs) have been proven to be a useful tool to complement clinical assessment and to detect residual cognitive functions in patients with disorders of consciousness. These ERPs are of ten recorded using passive or unspecific instructions. Patient data obtained this way are then compared to data from healthy participants, which are usually recorded using active instructions. The present study investigates the effect of attentive modulations and particularly the effect of activevs. passive instruction on the ERP components mismatch negativity (MMN) and N400. A sample of 18 healthy participants listened to three auditory paradigms: anoddball, aword priming, and a sentence paradigm. Each paradigm was presented three times with different instructions: ignoring auditory stimuli, passive listening, and focused attention on the auditory stimuli. After each task, the participants indicated their subjective effort. The N400 decreased from the focused task to the passive task, and was extinct in the ignore task. The MMN exhibited higher amplitudes in the focused and passive task compared to the ignore task. The data indicate an effect of attention on the supratemporal component of the MMN. Subjective effort was equally high in the passive and focused tasks but reduced in the ignore task. We conclude that passive listening during EEG recording is stressful and attenuates ERPs, which renders the interpretation of the results obtained in such conditions difficult.
Conflict Management
(2014)
Humans have a remarkable ability to plan ahead, set goals for the future and then to act accordingly. Unfortunately, this is not always the case. Everybody has experienced situations in which motivational urges like a tendency to drink another beer, or over-learned behavioral routines like driving on the right side of the road collide with ones´ goals. This tug of war between impulsive or habitual action tendencies and goal-directed actions is called a conflict.
Conflict is ubiquitous and comes in many different ways. Not surprisingly, the means to control conflict are diverse, too. Clearly, people can manage conflict in multiple ways: When expecting a conflict situation to occur in the future, one can recruit more effort to resolve the conflict, for instance by inhibiting unwanted urges or habits. Alternatively one can avoid the conflict situation and thereby circumvent possible failures to control habits and impulses. Furthermore, when currently facing a conflict, people can mobilize more effort to overcome the conflict. Alternatively they can withdraw from the conflict situation to minimize the risk of indulging in their impulses and habits.
To account for these different ways to master a conflict, the present thesis takes an initial step towards a characterization of the variability of control. To this aim, two dimensions of control will be identified that result from partially incompatible constraints on action control. These dimensions depict a trade-off between flexibility and stability and between anticipatory early selection and reactive late correction of control parameters. To describe how these control trade-offs interact and to explain how conflict is handled to ensure adaptation behavior, the conflict management framework is proposed. A corollary of this framework suggests that one strategy to control conflict comprises of a tendency to withdraw from a conflict situation.
The empirical part probed this behavioral response to conflict and tested whether participants withdraw from conflict situations. To approach this hypothesis, three series of experiments are presented that employ free choice paradigms, speeded response classification tasks and continuous movement tracking tasks to reveal withdrawal from conflict. Results show that conflict caused motivational avoidance tendencies (Experiment 1 &2), biased decision making away from conflict tasks (Experiment 3 & 5) and affected the execution of more complex courses of action (Experiment 6 & 7).
The results lend support for the proposed conflict management framework and provide the ground for a more thorough treatment of how the different conflict strategies can be integrated. As a first step, a connectionist model is presented that accounts for the simultaneous implementation of two conflict strategies observed in Experiments 3 – 5. The remainder of the present thesis analyses failures to integrate different conflict strategies. It is discussed how the conflict management framework can shed light on selected psychopathologies, inter-individual differences in control and break-downs of self-control.
Lesen ist keine passive Rezeption schriftlichen Materials, sondern eine aktive, wechselseitige Beeinflussung von Text und Leser. Der Erwerb von Lesekompetenz ist daher ein komplexer und langwieriger Prozess, der nicht mit der Alphabetisierung in der Grundschule endet, sondern bis ins Erwachsenenalter hinein andauert.
In nationalen und internationalen Studien zeigten deutsche Jugendliche zum Teil gravierende Defizite im Hinblick auf die Lesekompetenz. Inzwischen wurden zwar zahlreiche Einflussfaktoren und Ansatzpunkte für Fördermaßnahmen identifizifiziert und Interventionen konzipiert. Um diese Maßnahmen jedoch gezielt und gewinnbringend einsetzen und evaluieren zu können, ist es erforderlich, den Leistungsstand der Schüler umfassend zu erheben. Bislang fehlten hierfür geeignete Diagnoseinstrumente für die mittleren und höheren Klassenstufen. Daher wurden im Projekt "LESEN - Lesen ermöglicht Sinnentnahme" zwei Lesetests für die Sekundarstufe entwickelt: LESEN 6-7 für die Klassenstufen sechs und sieben sowie LESEN 8-9 für die Klassenstufen acht und neun.
LESEN 6-7 und LESEN 8-9 sind zwei analog aufgebaute Lesetests, die vor allem auf die kognitiven Aspekte der Lesekompetenz, also das Leseverständnis, fokussieren. Beide Tests enthalten jeweils zwei Subtests: Basale Lesekompetenz (BLK) und Textverständnis (TV). Der Subtest BLK besteht aus einer Satzleseaufgabe und erfasst die Lesegeschwindigkeit und das Verständnis einfacher, kurzer Sätze. Der Subtest TV enthält einen expositorischen und einen narrativen Text mit geschlossenen Verständnisfragen, die die inhaltliche Verarbeitung prüfen. Damit orientiert sich der Aufbau der Tests am aktuellen Forschungsstand, demzufolge Leseverständnis sich aus basalen Prozessen und hierarchiehöheren Verständnisleistungen zusammensetzt. Bezüglich des Verständnisses werden in der Literatur verschiedene Verarbeitungsebenen beschrieben, die bei der Konstruktion des Subtests TV explizit Berücksichtigung fanden.
Methodisch orientierte sich die Konstruktion von LESEN 6-7 und LESEN 8-9 zunächst an der Klassischen Testtheorie (KTT). Während für den Subtest BLK darüber hinaus kein Testmodell nötig war, da die Anzahl der in der vorgegebenen Zeit gelesenen Sätze bereits eine metrische Variable darstellt, wurde dem Subtest TV das dichotome Rasch-Modell zugrunde gelegt. Bei Letzterem wurden daher zusätzlich entsprechende Rasch-Kennwerte für die Itemselektion herangezogen. Beide Tests wurden an einer großen Stichprobe, die jeweils Schüler mehrerer deutscher Bundesländer und verschiedener Schularten einschloss, normiert. Zudem wurden jeweils beide Subtests eingehend auf Reliabilität und Validität sowie weitere gängige Testgütekriterien geprüft. Der Subtest TV wurde darüber hinaus auf Rasch-Modell-Konformität untersucht.
Die Ergebnisse der empirischen Erprobung der beiden Tests fallen sehr zufriedenstellend aus. Die Normstichprobe umfasst 1.644 Schüler für LESEN 6-7 und 945 Schüler für LESEN 8-9. Sowohl die KTT- als auch die Rasch-Kennwerte für die Reliabilität liegen im mittelhohen bis hohen Bereich. Die inhaltliche Validität ergibt sich aus den stringent aus der Theorie abgeleiteten Iteminhalten. Die Konstruktvalidität wird durch größtenteils hohe bis sehr hohe Korrelationen mit konstruktnahen Skalen gestützt. Im Sinne konvergenter Validität korrelieren die Ergebniswerte von LESEN 6-7 und LESEN 8-9 außerdem höher mit konstruktnahen Außenkriterien (Lehrerurteil zur Lesekompetenz, Deutschnote) als mit konstruktfernen Außenkriterien (Gesamtnotenschnitt, Mathematiknote). Die niedrige bis nicht vorhandene Korrelation mit konstruktfernen Außenkriterien weist auf diskriminante Validität der Tests hin. Weiter sprechen die größtenteils erwartungskonformen Ergebnisse im Hinblick auf verschiedene aus der Theorie und empirischen Vorbefunden abgeleitete Hypothesen u. a. in Bezug auf Klassenstufen- und Schulartunterschiede für die Validität von LESEN 6-7 und LESEN 8-9. Die Ergebnisse der Rasch-Modell-Konformitätsprüfung für den Subtest TV sprechen für das Vorliegen von Itemhomogenität in beiden Tests, jedoch eher gegen das Vorliegen von Personenhomogenität.
Insgesamt erfüllen LESEN 6-7 und LESEN 8-9 gängige Testgütekriterien in zufriedenstellendem
Maße. Sie ermöglichen sowohl auf Gruppen- als auch auf Individualebene eine umfassende Erfassung des Leseverständnisses von Sekundarschülern sowie in allen vier Klassenstufen eine Differenzierung im gesamten Leistungsspektrum.
Our current environment is characterized by the omnipresence of food cues. The sight and smell of real foods, but also graphically depictions of appetizing foods, can guide our eating behavior, for example, by eliciting food craving and influencing food choice. The relevance of visual food cues on human information processing has been demonstrated by a growing body of studies employing food images across the disciplines of psychology, medicine, and neuroscience. However, currently used food image sets vary considerably across laboratories and image characteristics (contrast, brightness, etc.) and food composition (calories, macronutrients, etc.) are often unspecified. These factors might have contributed to some of the inconsistencies of this research. To remedy this, we developed food-pics, a picture database comprising 568 food images and 315 non-food images along with detailed meta-data. A total of N = 1988 individuals with large variance in age and weight from German speaking countries and North America provided normative ratings of valence, arousal, palatability, desire to eat, recognizability and visual complexity. Furthermore, data on macronutrients (g), energy density (kcal), and physical image characteristics (color composition, contrast, brightness, size, complexity) are provided. The food-pics image database is freely available under the creative commons license with the hope that the set will facilitate standardization and comparability across studies and advance experimental research on the determinants of eating behavior. Read F