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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Cerebral Asymmetries, Motivation, and Cognitive Processing: An Analysis of Individual Differences

Düsing, Rainer 17 July 2015 (has links)
Everyday life experience tells us that individual differences apparently matter. Although confronted with the same situation, individuals seem to act and react in different ways. On a behavioral and self-report level, individual differences are well documented. Over the past decades, they have been systematically assessed and embedded in complex theories of personality. On the other hand, the influence of personality differences on cognitive processes and their cerebral substrate is far from being entirely understood. Especially the complex interplay of two or more aspects, like individual differences (e.g., in motivational processes), cognitive functions (e.g., intuition), cerebral activation and lateralization, and humoral processes (e.g., cortisol), are seldom aim of psychological research. The Personality Systems Interaction (PSI) theory (Kuhl, 2000, 2001) provides a theoretical framework, which tries to incorporate the above-mentioned aspects. On the background of PSI theory, the aim of the present work was to investigate differences in motivational processing and how they are related to hemispherical asymmetries, cognitive processing, and humoral reactivity. Each of the three research articles presented throughout the present work tackles different aspects of this general research question. For this, a variety of different methodological techniques were used (e.g., questionnaires, implicit measures, electroencephalography, etc.) to approach the aforementioned goal. The first research paper presented in the current work examines the relationship between the implicit affiliation motive and intuition, as a form cognitive processing. Previous research already demonstrated that affiliation-laden primes facilitate intuitive thought (Kuhl & Kazén, 2008). Therefore, it could be expected that trait affiliation motive would also be correlated with intuition. Intuition in turn is thought to be a function of right hemispheric processes. An association between trait affiliation and intuition could therefore indirectly indicate a lateralization to the right side for affiliation. With the first study of the present work, the author tested this association. Thirty-nine students filled in the Operant Motive Test for the assessment of implicit affiliation, a variant of the Thematic Apperception Test. Then, 9 months later, participants engaged in a Remote Associates Test in which they intuitively had to indicate whether three words are semantically related. As expected, the implicit affiliation motive significantly predicted the accuracy of identifying related word triads. No other implicit or explicit measure, nor state or trait positive affect was associated with intuition. With the second research article, the aforementioned indirect association between affiliation and lateralized processing was investigated more directly. Previous research on relationships between personality and EEG resting state frontal asymmetries mainly focused on individual differences with respect to motivational direction (i.e., approach vs. withdrawal). By contrast, the second article investigated frontal asymmetries as a function of individual differences in implicit affiliation motive. The goal was not only to contribute to the validation of PSI theory and to the investigation of the laterality of the affiliation motive, but also to disentangle the contribution of different social motives to frontal EEG asymmetries. The consideration of social motives, such as the affiliation motive, seemed to be necessary, because a recent meta-analysis showed that the association between approach motivation and frontal asymmetries is negligible or that unidentified moderators drive this association. From previous research and the results from the first paper presented in the current work, an association between affiliation motive and right frontal activity was predicted. Additionally, to control for possible associations with motivational direction, trait behavioral inhibition, behavioral activation, and anger were assessed and correlated with frontal asymmetries. Seventy-two right-handed students were tested. As expected and in accordance with the findings from the first paper, the author found that relative right frontal activity (indicated by low alpha frequency power) was associated with the affiliation motive. To explore brain regions responsible for this association at scalp sites, a source localization algorithm was applied. Intracranial distribution of primary current densities for the alpha band spectrum in source space was estimated and correlated with implicit affiliation scores. A significantly correlating area could be identified in the right ventromedial prefrontal cortex (Brodmann Area 10). No other associations at scalp sites or in source space could be found for motivational direction. The third research article presented in the current work highlights motivational differences slightly different from those presented above. It deals with dynamic motivational processes, such as action orientation, and how they moderate the association between cerebral asymmetries and the physiological stress reaction. Hypothalamus pituitary adrenocortical (HPA) system activity and frontal brain asymmetries have both been linked to stress and emotion but their relationship remains unclear, especially when additionally considering individual differences. Therefore, participants were exposed to public speaking stress while salivary cortisol levels (as a marker of HPA activity) and resting frontal EEG alpha asymmetries were assessed before and after stress induction. The results indicate that higher post stressor cortisol levels were associated with higher relative left frontal activity. State oriented participants showed a stronger association between cortisol response and left frontal activity than action oriented participants. The above-mentioned findings are discussed referring to PSI theory and their possible implications. Additionally, shortcomings of the present research and possible remedies will be presented.
2

Stress effects on human fear conditioning and the role of female sex hormones

Antov, Martin I. 18 December 2015 (has links)
Classical fear conditioning – including acquisition and extinction – is a model for fear learning and memory in health and disease. Moreover, trauma-related disorders can be viewed as comprising fear acquisition under severe stress. Yet, in humans, we know comparatively little about how acute stress affects fear conditioning. Therefore, the first aim of this thesis was to investigate the effect of stress on fear acquisition or extinction. Stress induces multiple hormonal and neurotransmitter changes dynamically developing over time, including a fast first-wave and a slower second-wave stress response. Models derived from avoidance learning and declarative memory studies suggest that stress effects on memory depend on the temporal proximity between learning and stressor: encoding close to the stressor will be enhanced, but encoding and recall later in time (during the second-wave) will be suppressed (e.g., Schwabe, Joëls, Roozendaal, Wolf, & Oitzl, 2012). So far, these predictions were not related to fear conditioning. Therefore, we investigated if the model-based predictions are also valid in human fear conditioning. We used two stressors to investigate first-wave and second-wave stress effects: the cold pressor test (CPT) inducing a strong first-wave but little second-wave activation and a psychosocial stressor, reliably inducing both, first- and second-wave stress responses. Conditioning was measured via skin conductance responses (SCRs). Investigating the first-wave (Experiment 2), we placed fear acquisition and immediate extinction directly after the CPT (n = 20) or after the control treatment (n = 20). We found no group difference in acquisition performance, but significantly increased extinction resistance in the stressed CPT group. In Experiment 3, CPT (n = 20) or control (n = 20) was placed after acquisition but directly prior to extinction training. Here, we found improved extinction and 24h-delayed extinction recall after CPT. Investigating the second-wave (Experiment 1), we placed fear acquisition and immediate extinction 45 min after the psychosocial stressor (i.e., at the peak of salivary cortisol, n = 12) or after control (n = 12). Here, we found no significant stress effects. Sex and female sex hormones also influence fear conditioning: Women are at a higher risk to develop anxiety and stressor-related disorders than men. Interestingly, patients with these disorders show impaired fear extinction and extinction recall, and low levels of the sex hormone 17β-estradiol (E2) are linked to impaired extinction in both, healthy and patient female samples. So far, there is little data on how acute stress and circulating E2-levels might interact in fear acquisition and especially in fear extinction. Therefore, the second aim of this thesis was to explore this possible interaction in healthy women in different cycle phases compared to men. Thus, in Experiment 4, we included hormone status as a quasi-experimental variable and compared free cycling women in the midcycle phase (high E2, low progesterone, n = 24), women in the early follicular phase of the menstrual cycle (low E2, low progesterone, n = 24), and men (n = 24). We placed fear acquisition and extinction 45 min after the psychosocial stressor (n = 36) or control (n = 36), and tested extinction recall after 24 h. In line with Experiment 1, the second-wave stressor did not affect fear acquisition and immediate extinction. However, we found a stress by hormone status interaction within women at the 24h-delayed extinction recall test: in the stressed group, early follicular women showed impaired extinction recall and a higher return of fear compared to midcycle women, whereas there was no difference between early follicular and midcycle women after control treatment. Collectively our results support a different role for the first- and second-wave stress response in human fear conditioning. Fear acquisition near the first-wave stress response results in enhanced fear memory, which is resistant to extinction. Extinction training near the first-wave enhances extinction learning. In contrast, fear conditioning at the peak of the peripheral second-wave cortisol response had no effect on acquisition or extinction performance. However, second-wave stress interacted with the hormone status of women, where only women in a low E2 state were vulnerable to negative stress effects in extinction recall. The last result will encourage further investigation of the interplay between E2 and stress in fear extinction. Enhancement of extinction by the CPT could – if replicated – be translated into strategies for optimizing exposure therapy.
3

Körperliche Reinigung und psychische Funktionen

Kaspar, Kai 23 December 2015 (has links)
Psychische Ursachen und Effekte körperlicher Reinigung waren lange Zeit nur ein Randthema psychologischer Forschung. Inspiriert durch die in vielen Religionen und Medien häufig thematisierte metaphorische Verbindung zwischen körperlicher und moralischer Reinheit konnte in den letzten Jahren substantielle empirisch Evidenz für einen tatsächlichen psychologischen Mechanismus gefunden werden. Dabei zeigte sich auch, dass körperliche Reinigung über die Domäne moralischer Selbstbilder und Urteile hinaus bedeutsame Effekte auf psychische Funktionen haben kann. Die vorliegende Arbeit stellt die Entwicklung und den aktuellen Stand dieser Forschungslinie dar. Insbesondere beinhaltet sie fünf empirische Studien, die verschiedene Facetten körperlicher Reinheit mit Blick auf psychische Funktionen untersuchen. In Studie 1 wird erstmalig demonstriert, dass Händewaschen nach einem Misserfolgserlebnis in einer kognitiven Problemlöseaufgabe den Optimismus, zukünftig eine bessere Leistung zeigen zu können, signifikant steigerte, dabei jedoch die tatsächliche spätere Leistung reduzierte. In Studie 2 wird vor dem Hintergrund unterschiedlicher theoretischer Annahmen über die Wirkung von körperlicher Reinigung gezeigt, dass Händewaschen die Tendenz verstärkter stereotyper moralischer Urteile abschwächt und gleichzeitig die Herunterregulierung physiologischer Erregung begünstigt. Dabei wird erstmalig eine Blickbewegungs- und Pupillometrie-Messung im Forschungsfeld durchgeführt, um objektive Indikatoren für Informationsaufnahmeprozesse und physiologische Erregung zu nutzen. In Studie 3 wird demonstriert, wie ausgehend von der Annahme einer modulierten Gewichtung kognitiver Information durch Händewaschen dieses die Gedächtnisleistung für moralische und unmoralische Inhalte zugunsten letzterer verändert. Studie 4 untersucht, wie die aktive Reinigung der Hände sowie die bloße Aktivierung von Reinheitskognitionen die eingeschätzte Wahrscheinlichkeit für zukünftige moralische und unmoralische Handlungen beeinflusst. Schließlich untersucht Studie 5 die potentielle Interaktion zweier haptischer Informationseinflüsse, indem Händereinigen und Gewichtsempfindungen kombiniert werden. Die Ergebnisse der Studien liefern eine Vielzahl neuer Befunde, die einem besseren Verständnis psychologischer Effekte körperlicher Reinheit dienen und insbesondere mit Blick auf das konzeptionelle Rahmenmodell der Embodied Cognition wichtige Erkenntnisse liefern.
4

Progression in cognitive-affective research by increasing ecological validity: A series of Virtual Reality studies.

Kisker, Joanna 18 February 2022 (has links)
The ultimate aim of psychological research is to disentangle everyday human functioning. Achieving this goal has always been limited by the necessity of balancing experimental control and ecological validity. Recent technical advances, however, reduce this trade-off immensely, perhaps even rendering it void: Sophisticated virtual reality (VR) systems provide not only high experimental control but also multidimensional and realistic stimuli, tasks, and experimental setups. Yet prior to applying VR as a standalone experimental method, an empirical foundation for its application needs to be established. To this end, this dissertation aims to shed light on whether and which changes in cognitive-affective standard findings result from increasing the ecological validity by means of VR paradigms. The four empirical studies included in this dissertation focus either on the affective or mnemonic processes and mechanisms occurring under immersive VR conditions compared to conventional laboratory setups. Study 1.1 investigated whether the electrophysiological correlates of the approach/avoidance dimension differ depending on the mode of presentation, i.e., immersive VR footage or a virtual 2D desktop. Study 2 was extended by a behavioral component. Full-body responses were enabled within this paradigm to examine holistic fear responses and to put to the test whether the respective electrophysiological responses translate from keystrokes to natural responses. With respect to the retrieval of such immersive experiences, Study 1.2 aimed to replicate the memory superiority effect found for VR conditions compared to conventional conditions. The generalizability of this effect will be examined using complex, multimodal scenes. Going one step further, Study 3 differentiated the retrieval mechanisms underlying VR-based or conventional laboratory engrams on the electrophysiological level. The well-established theta old/new effect served as a benchmark to check whether cognitive processes obtained under conventional conditions translate to VR conditions. The results of these studies are discussed with respect to whether and how increasing ecological validity alters the standard findings expected on the basis of the previous research background. Special attention will be paid to the differences between conventional laboratory setups and sophisticated VR setups with the aim to identify possible sources of the obtained deviations from standard findings. Such changes in the findings that overlap and exceed all studies beyond their primary focus, whether emotional or mnemonic, are discussed in terms of embodied simulations and the predictive coding hypothesis. A shared mental 3D default space is proposed as a possible source of fundamental differences between conventional and VR-based research outcomes. In particular, it will be demonstrated that conventional research approaches and findings may not only be amplified but fundamentally altered when translated to VR paradigms.
5

Embodied emotions: The role of sex hormones in emotional processing

Gamsakhurdashvili, Dali 15 June 2021 (has links)
Emotion, as well as cognition, are often understood as a manifestation of brain activity. However, bodily processes are also involved in mental functioning, referring to the concept of embodiment. Embodied emotion, traditionally, implies that experiencing an emotion involves perceptual, somato-visceral, and motor aspects. Within the frame of the Research Training Group “Situated Cognition”, we here extend the concept of embodiment by considering the role of hormones in the processing of emotional content. Importantly, hormones allow a bidirectional body-to-brain and brain-to-body coupling. The endocrine system, e.g., steroid sex hormones, produced in the gonads, send feedback to the brain by binding at their receptors. These receptors are relatively abundant in the brain regions associated with emotional processing, memory, and executive functions (i.e., amygdala, hippocampus, and prefrontal cortex). Moreover, peripheral hormone secretion is modulated via actions from the central nervous system. We intended to characterize the role of sex hormones, and partly also of stress hormones, on different components of emotion as a hormonal embodiment of emotion. Thus, we examined emotional processing in different sex hormone-status groups. To account for different levels of sex hormones, we used a quasi-experimental approach by comparing women in different cycle phases, women using hormonal oral contraceptives (Study 1), and additionally men (in Study 2). The female menstrual cycle is characterized by fluctuating sex hormone levels. On the peripheral gonadal level, these are 17β-estradiol and progesterone. These hormones are low at the beginning of the cycle (early follicular phase). Estradiol rises towards the middle of the cycle (mid-cycle) and stays moderately high until the next cycle. Progesterone levels are high after mid-cycle in the luteal phase until the end of the cycle. Hormonal contraceptives suppress the endogenous production of estradiol and progesterone, keeping the hormone levels low during the whole cycle. Estradiol and progesterone are also present in males, however, at low levels with no sign of cyclical fluctuations. In Study 1, we examined three independent groups of women in the mid-cycle (n = 24), in the luteal phase (n = 24), and women using hormonal oral contraceptives (n = 24). We assessed different measures of emotional processing, i. e. emotional memory, cognitive and affective empathy-related measures (emotion recognition and ratings for feeling with a protagonist´s emotion, respectively), as well as mimic and skin-conductance responses to affective stimuli. Additionally, we addressed interactions of experimental stress (cold pressor test vs. control) with sex hormones in emotional memory. Our data demonstrated the role of hormones in empathy-related measures and skin-conductance responses depending on the stimulus characteristics (valence, the gender of the protagonist). Emotional memory was not affected by hormone status, stressor or salivary hormone levels. In the cognitive empathy-related measure, women in the luteal phase, as well as oral contraceptive users, identified emotions depicted by female protagonists more accurately than those by male protagonists. On the other hand, estradiol correlated positively with recognition of emotions depicted by males in the total sample. In the affective empathy-related measure, oral contraceptive users rated negative emotions higher than the positive ones. Finally, in the luteal phase skin-conductance responses to negative stimuli were heightened, also supported by a positive correlation with the salivary progesterone levels. The mimic responses remained unaffected. None of the remaining associations with the salivary hormone levels were significant. These results indicate that sex hormones modulated emotional processing by interacting with the stimulus features, as evident in the negativity bias under oral contraceptive use and in the luteal phase in the affective empathy-related measure and sympathetic autonomous reactivity, respectively. However, emotional memory and mimic activity to affective stimuli were not affected. In Study 2, we extended the initial scope to examine the role of sex hormones and olfaction in empathy-related measures. Reports of female advantage in empathy-related measures suggest a role for sex hormones, although data are inconsistent. Studies also report similar sex differences in human olfactory perception. In rodents, olfaction is involved in detecting and integrating socially-relevant information and is modulated by the brain-actions of estrogens. Based on this background, we hypothesized that olfaction may untangle the mixed evidence regarding the relationship between sex hormones and empathy-related measures (cognitive, affective). Thus, we measured odor discrimination ability, empathy-related measures, and facial mimic activity (also associated with affective empathy-related measures) in free-cycling women in high sex-hormone phases (n = 20), oral contraceptive users (n = 19), and men (n = 21). Free-cycling women outperformed only men in the recognition of emotions depicted from the eye region. Oral contraceptive users showed higher scores in the affective empathy-related measure towards negative emotions. Free-cycling women exhibited the strongest facial mimicry (viewing female, but not male protagonists), positively associated with progesterone. Finally, the groups differed in odor discrimination, with free-cycling women outperforming men. However, odor discrimination ability and empathy-related performance were not correlated. Our results support the role of sex hormones in odor perception and empathy-related measures, to a certain extent. However, no common underlying mechanism was found. Finally, we conducted a systematic review (Study 3) aiming to elucidate factors contributing to the inconsistent results concerning the role of sex hormones in the two most addressed areas of emotional processing, emotion recognition (empathy-related measure) and emotional memory. Thereby, we extended previous reviews that address single areas of emotion processing. Moreover, we systematically addressed the role of situational features (mainly emotion-type and/or stimulus valence). All studies included healthy women of reproductive age either in stages of their natural menstrual cycle or using oral contraceptives, and measured or at least estimated levels of ovarian sex hormones. We document the methodological diversity in the field, presumably contributing to the heterogeneity of results. We recognized the need for studies explicitly contrasting the early follicular, mid-cycle, and mid-luteal phases, as well as OC-intake and using standardized tasks. Research would take advantage of using within-subject design more frequently and account for the recognition of complex emotions. In sum, our data suggest that sex hormones differentially modulate the cognitive and affective empathy-related performance and skin-conductance responses by interacting with situational variables, such as the emotional valence of the stimuli and the gender of the protagonist. Women in the luteal phase and under oral contraceptive use demonstrated better recognition of emotions depicted by female protagonists. By contrast, estradiol levels positively correlated with the recognition of emotions depicted by male protagonists. Sex-hormone status main effects only manifested in the emotion recognition advantage of free-cycling women over men (Reading the Mind in The Eyes Test; Study 2). In both studies, affective empathy ratings towards negative emotions were higher in the oral contraceptive users. Moreover, although mimic activity was not associated with sex hormones, skin-conductance responses to negative stimuli were heightened in the luteal phase. On the other hand, the performance in empathy-related measures in different hormone-status groups was not related to odor discrimination ability. Additionally, the inconsistencies of the sex hormone and emotion research could be the result of variations of designs and tasks used across studies from a similar field. This is also indicated in our findings from the empathy-related measures differing in tasks and hormone-status groups in two studies. Finally, our findings provide evidence that emotional processes under sex-hormone modulation are situated, i.e., subject to the influence of the stimulus valence. Furthermore, they are embodied via coupling between the endocrine system and the brain as evident in hormone status and valence interactions in empathy-related measures and sympathetic reactivity.
6

Individual Differences in Emotion Regulation Abilities: Action Orientation’s Impact on Intuition, Negativity Bias in Depression, and Self-Infiltration

Radtke, Elise L. 21 January 2020 (has links)
Using action orientation after failure as a measure of individual differences in emotion regulation abilities (ERA), this thesis’ studies investigated the impact of ERA on cognition, behavior, and own versus imposed goals differentiation. The first study used cortisol as a physiological stress marker to replicate the link between ERA and the ability to make intuitive judgments under stress. High ERA were associated with increased performance in an intuition task under stress. In contrast, when feeling no stress, low ERA were associated with increased performance in an intuition task. The second study showed that ERA can compensate for depression-associated biased processing of negative stimuli. This effect was present even at mild to moderate depression levels. Replicating earlier findings, the third study showed that ERA are associated with an increased ability to distinguish self-chosen from imposed goals. Most importantly, the study identified activation in the right medial prefrontal cortex as a neural correlate of identifying self-chosen goals, and activation in the anterior cingulate cortex, as a correlate of falsely identifying imposed goals as self-chosen ones. Altogether, these studies show the necessity to consider individual differences in ERA in stress, clinical, and motivational research. The findings are discussed with respect to three theories that relate to motivation and personality from behavioral and neurobiological perspectives, namely, Personality Systems Interaction Theory, Predictive and Reactive Control Systems Theory, and Self-Determination Theory.
7

Low Intensity Transcranial Electrical Stimulation: Effects on Categorization and Methodological Aspects / Transkranielle Stromstimulation mit geringen Intensitäten: Die Effekte auf Kategorisierungsleistung und methodische Aspekte

Ambrus, Géza Gergely 21 May 2012 (has links)
No description available.
8

Virtuelle Nothilfe - Ein Experiment zum Effekt von virtueller Hilfe, Gewalt und Nothilfe auf Hilfe- und Gewaltverhalten / Virtual Emergency Assistance - The Effect of Virtual Helping, Aggression and Emergency Assistance on Helping and Aggressive Behavior

Mohseni, M. Rohangis 23 July 2013 (has links)
A recent meta-analysis of Anderson and colleagues (2010) shows that violent behavior in computer games promotes violent behavior in real-life and inhibits prosocial behavior. A couple of studies conducted by Greitemeyer and Osswald (2010) lead to the conclusion that helping behavior in computer games furthers helping behavior in real-life. There exist no studies examining the combined effect of violence and helping in computer games, although this combination is typical for violent video games (Anderson et al., 2010). In violent RPGs, a lot of tasks consist of helping someone by using violence. The present study addresses this issue and bridges the current empirical gap by investigating if violent emergency assistance furthers helping behavior and/or violent behavior in real-life. To accomplish that, the role-playing game “Oblivion” was modified to create four different experimental conditions: (1) violent emergency assistance, (2) killing, (3) helping, and (4) treasure hunting. Comparing these conditions, violent emergency assistance seemingly reduces helping behavior in real-life and at the same time furthers violent behavior. The results are in unison with the moral management model (Hartmann & Vorderer, 2010; Hartmann, in press), which is based on Banduras Theory of Moral Disengagement (Bandura, 2002).
9

Context Effects in Early Visual Processing and Eye Movement Control

Nortmann, Nora 29 April 2015 (has links)
There is a difference between the raw sensory input to the brain and our stable perception of entities in the environment. A first approach to investigate perception is to study relationships between properties of currently presented stimuli and biological correlates of perceptual processes. However, it is known that such processes are not only dependent on the current stimulus. Sampling of information and the concurrent neuronal processing of stimulus content rely on contextual relationships in the environment, and between the environment and the body. Perceptual processes dynamically adjust to relevant context, such as the current task of the organism and its immediate history. To understand perception, we have to study how processing of current stimulus content is influenced by such contextual factors. This thesis investigates the influence of such factors on visual processing. In particular, it investigates effects of temporal context in early visual processing and the effect of task context in eye movement control. To investigate effects of contextual factors on early visual processing of current stimulus content, we study neuronal processing of visual information in the primary visual cortex. We use real-time optical imaging with voltage sensitive dyes to capture neuronal population activity in the millisecond range across several millimeters of cortical area. To characterize the cortical layout concerning the mapping of orientation, previous to further investigations, we use smoothly moving grating stimuli. Investigating responses to this stimulus type systematically, we find independent encoding of local contrast and orientation, and a direct mapping of current stimulus content onto cortical activity (Study 1). To investigate the influence of the previous stimulus as context on processing of current stimulus content, we use abrupt visual changes in sequences of modified natural images. In earlier studies, investigating relatively fast timescales, it was found that the primary visual cortex continuously represents current input (ongoing encoding), with little interference from past stimuli. We investigate whether this coding scheme generalizes to cases in which stimuli change more slowly, as frequently encountered in natural visual input. We use sequences of natural scene contours, comprised of vertically and horizontally filtered natural images, their superpositions, and a blank stimulus, presented with 10 or 33 Hz. We show that at the low temporal frequency, cortical activity patterns do not encode the present orientations but instead reflect their relative changes in time. For example, when a stimulus with horizontal orientation is followed by the superposition of both orientations, the pattern of cortical activity represents the newly added vertical orientations instead of the full sum of orientations. Correspondingly, contour removal from the superposition leads to the representation of orientations that have disappeared rather than those that remain. This is in sharp contrast to more rapid sequences for which we find an ongoing representation of present input, consistent with earlier studies. In summary, we find that for slow stimulus sequences, populations of neurons in the primary visual cortex are no longer tuned to orientations within individual stimuli but instead represent the difference between consecutive stimuli. Our results emphasize the influence of the temporal context on early visual processing and consequentially on information transmission to higher cortical areas (Study 2). To study effects of contextual factors on the sampling of visual information, we focus on human eye movement control. The eyes are actively moved to sample visual information from the environment. Some traditional approaches predict eye movements solely on simple stimulus properties, such as local contrasts (stimulus-driven factors). Recent arguments, however, emphasize the influence of tasks (task context) and bodily factors (spatial bias). To investigate how contextual factors affect eye movement control, we quantify the relative influences of the task context, spatial biases and stimulus-driven factors. Participants view and classify natural scenery and faces while their eye movements are recorded. The stimuli are composed of small image patches. For each of these patches we derive a measure that quantifies stimulus-driven factors, based on the image content of a patch, and spatial viewing biases, based on the location of the patch. Utilizing the participants’ classification responses, we additionally derive a measure, which reflects the information content of a patch in the context of a given task. We show that the effect of spatial biases is highest, that task context is a close runner-up, and that stimulus-driven factors have, on average, a smaller influence. Remarkably, all three factors make independent and significant contributions to the selection of viewed locations. Hence, in addition to stimulus-driven factors and spatial biases, the task context contributes to visual sampling behavior and has to be considered in a model of human eye movements. Visual processing of current stimulus content, in particular visual sampling behavior and early processing, is inherently dependent on context. We show that already in the first cortical stage, temporal context strongly affects the processing of new visual information and that visual sampling by eye movements is significantly influenced by the task context, independently of spatial factors and stimulus-driven factors. The empirical results presented provide foundations for an improved theoretical understanding of the role of context in perceptual processes.
10

I can't let go: Personality, Behavioral, and Neural Correlates of Persistent, Intrusive Thought in Depression

Eggert, Lucas 24 April 2013 (has links)
Though a major illness in modern society, depression is still not completely understood. A number of empirical observations point to the importance of basic cognitive processes as well as personality variables as antecedents of a depressive disorder. In this work it is argued that “state orientation”, a personality style characterized by the inability to actively influence one’s focus of thought, plays an important role in the development of at least some forms of major depressive disorder. In the present work, it is suggested that (1) state-oriented cognitions are equivalent to sustained information processing, that (2) depressed individuals are characterized in particular by state-oriented cognitions related to prior failure experiences, that (3) sustained processing of affective information will interfere with normal executive cognitive functioning in depressed individuals resulting in impairments of normal behavior, and that (4) both sustained information processing and “affective interference” will be associated with specific dysfunctional patterns of brain activity in depressed individuals. In the first chapter of this thesis, theorizing pertaining to “action control” and the relationship between action control and state orientation are reviewed. After having established the potential functional significance of state-oriented cognitions, their possible link to depression is developed by introducing the “degenerated-intention hypothesis”. Afterwards, the role of state orientation in the advent of the depressive state is discussed against the background of the “functional helplessness” model of depression. Next, recent empirical findings related to executive dysfunction associated with state-oriented cognitions in major depressive disorder and related dysfunctional patterns of brain activity are reviewed. By considering evidence from studies on executive functioning, brain imaging, and neurophysiological studies, support is found for a possible frontocingulate dysfunction associated with a state-oriented cognitive style underlying a major depressive disorder. Consistent with the proposed link between depression and state orientation, in the second chapter of the thesis, Studies 1a – 1c demonstrate that subclinically and clinically depressed individuals are specifically characterized by failure-related state orientation. Moreover, the results of Study 2, described in Chapter 3, reveal that sustained processing of affectively valenced information may indeed interfere with subsequent executive cognitive functioning, especially in individuals demonstrating relatively high levels of depression. Finally, in line with the idea that sustained information processing and affective interference will be related to an individual’s level of state orientation and will be reflected in specific patterns of neural activity, Study 3, presented in Chapter 4, provides considerable evidence for disturbed brain function in clinically depressed individuals during processing of affective information as well as subsequent executive cognitive functioning and its relation to state-oriented thought. The current research supports the idea that state orientation, in particular its failure-focused form, is a crucial process involved in the development and maintenance of a depressive disorder. Specifically, the present findings suggest that certain forms of major depressive disorder are associated with sustained processing of affective information and with the resulting affective interference with executive cognitive functioning. Findings further suggest that sustained information processing is experienced by affected individuals as ruminative, state-oriented thought on past aversive experiences, and that both sustained information processing and affective interference are associated with distinct patterns of brain activity, which are related to early stimulus evaluation, conflict monitoring, and conflict resolution. The processes possibly underlying some forms of depression, as proposed in this thesis, comprise what may be called “the spinning mind”, whose important functional significance is to hinder an individual from adaptive behavior by impairing the ability to direct thought. Although state orientation may therefore appear to be maladaptive per se, it may be argued instead that this mode of action control is also an adaptive process as long as critical limits of certain parameters are met and the spinning mind is prevented. These and similar considerations are addressed in the concluding discussion in Chapter 5.

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