Adapting defensive behavior to the characteristics of a threatening situation is a fundamental function of the brain. Particularly, threat imminence plays a major role for the organization of defensive responses. Acute threat prompts phasic physiological responses, which are usually associated with an intense feeling of fear. In contrast, diffuse and potentially threatening situations elicit a sustained state of anxious apprehension. Detection of the threatening stimulus defines the key event in this framework, initiating the transition from potential to acute threat. Consequently, attention to threat is crucial for supporting defensive behavior. The functions of attention are finely tuned to the characteristics of a threatening situation. Potential threat is associated with hypervigilance, in order to facilitate threat detection. Once a threatening stimulus has been identified, attention is selectively focused on the source of danger. Even though the concepts of selective attention and hypervigilance to threat are well established, evidence for their neural correlates remain scarce. Therefore, a major goal of this thesis is to elucidate the neural correlates of selective attention to acute threat and hypervigilance during potential threat. A second aim of this thesis is to provide a mechanistic account for the interaction of fear and anxiety. While contemporary models view fear and anxiety as mutually exclusive, recent findings for the neural networks of fear and anxiety suggest potential interactions. In four studies, aversive cue conditioning was used to induce acute threat, while context conditioning served as a laboratory model of potential threat. To quantify neural correlates of selective attention and hypervigilance, steady-state visual evoked potentials (ssVEPs) were measured as an index of visuocortical responding. Study 1 compared visuocortical responses to acute and potential threat for high versus low trait-anxious individuals. All individuals demonstrated enhanced electrocortical responses to the central cue in the acute threat condition, suggesting evidence for the neural correlate of selective attention. However, only low anxious individuals revealed facilitated processing of the contexts in the potential threat condition, reflecting a neural correlate of hypervigilance. High anxious individuals did not discriminate among contexts. These findings contribute to the notion of aberrational processing of potential threat for high anxious individuals. Study 2 and 3 realized orthogonal combinations of cue and context conditioning to investigate potential interactions of fear and anxiety. In contrast to Study 1 and 2, Study 3 used verbal instructions to induce potentially threatening contexts. Besides ssVEPs, threat ratings and skin conductance responses (SCRs) were recorded as efferent indices of defensive responding. None of these studies found further evidence for the neural correlates of hypervigilance and selective attention. However, results for ratings and SCRs revealed additive effects of fear and anxiety, suggesting that fear and anxiety are not mutually exclusive, but interact linearly to organize and facilitate defensive behavior. Study 4 tested ssVEPs to more ecologically valid forms of context conditioning, using flickering video stimuli of virtual offices to establish context representations. Contrary to expectations, results revealed decreased visuocortical responses during sustained presentations of anxiety compared to neutral contexts. A disruption of ssVEP signals eventually suggests interferences by continuously changing video streams which are enhanced as a function of motivational relevance. In summary, this thesis provided evidence for the neural correlates of attention only for isolated forms of fear and anxiety, but not for their interaction. In contrast, an additive interaction model of fear and anxiety for measures of defensive responding offers a new perspective on the topography of defensive behavior. / ZusammenfassungDie Anpassung defensiver Verhaltensweisen an die Anforderungen bedrohlicher Sit-uationen ist eine fundamentale Funktion des Gehirns. Akute Bedrohung führt in der Regel zu kurz-anhaltenden, physiologischen Reaktionen, die mit einem Gefühlintensiver Furcht einhergehen, während Situationen potenzieller Bedrohung zu einem anhaltenden Zustand erhöhter Angst führen. Dabei spielt das Erkennen der Gefahr eine besondere Rolle, da sie den Übergang von potenzieller zu akuter Bedrohung initiiert. Demnach kommt der Aufmerksamkeit eine wichtige Funktion bei der Unterstützung defensiver Verhaltensweisen zu. Mechanismen der Aufmerksamkeit sind dabei präzise auf die jeweilige Situation abgestimmt. Potenzielle Bedrohung führt zu Hypervigilanz, um bedrohliche Reize schneller zu entdecken ...
| Identifer | oai:union.ndltd.org:uni-wuerzburg.de/oai:opus.bibliothek.uni-wuerzburg.de:23770 |
| Date | January 2021 |
| Creators | Stegmann, Yannik |
| Source Sets | University of Würzburg |
| Language | English |
| Detected Language | English |
| Type | doctoralthesis, doc-type:doctoralThesis |
| Format | application/pdf |
| Rights | https://creativecommons.org/licenses/by-nc-nd/4.0/deed.de, info:eu-repo/semantics/openAccess |
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