Disentangling the influence of stress (mediators) and time on fear generalization

Abstract

Under normal circumstances, the confrontation of a threatening situation or stimulus leads us to experience fear. To learn from those experiences, and adapt our behavior in upcoming situations when experiencing similar threats is important to protect our organism. Importantly, some people are not able to restrict their fear in future situations, but show an exaggerated fear also to actual safe conditions. This phenomenon is called fear overgeneralization and is thought to be an important contributor to anxiety and stress-related disorders. Thus, to investigate factors that may drive fear overgeneralization is of great relevance. We conducted four studies of which three directly examined possible contributing factors (time, stress and the major stress modulators cortisol and noradrenaline) to fear generalization in healthy participants using a two-day fear generalization paradigm. Taken together, we found that fear generalization increased over time without a change in the underlying neural mechanisms. However, we did not reveal any detrimental effects of stress on fear generalization, i.e. there was no fear overgeneralization due to stress. In contrast, it seems that an increase in noradrenergic arousal retains fear memory expression in more detail, thereby promoting an adequate level of fear generalization. Since the ability to predict a threat before it occurs, which is based on prior learning experiences, plays an important role in fear generalization, we conducted a fourth study. In this study, we investigated the influence of stress on attention during predictive fear learning using an aversive version of a blocking paradigm. Results suggest that stress impairs the ability to show a preferential attentional processing of stimuli, which are predictive of a forthcoming threat, when being confronted with the concurrent processing of multiple stimuli. Altogether, this thesis adds valuable information to the role of stress and time in fear learning, especially fear generalization. Whereas over time there seems to be an increase in fear generalization, stress does not have an additional impact, when fear learning is restricted to simple cue conditioning. However, our last study showed that stress influences attentional processing when multiple stimuli have to be processed at the same time. Therefore, I suggest that future studies should examine attentional processes in fear learning paradigms that require a simultaneous processing of multiple stimuli. This would resemble real world situations more closely and might help us to understand the development of anxiety and stress-related disorders.