Der Einfluss verschiedener Stressneuromodulatoren auf Risikoverhalten und Verlustaversion
Persönlichkeitspsychologie, Klinische und Medizinische Psychologie, Methoden
Zusammenfassung der Projektergebnisse
There is compelling evidence that the stress hormones cortisol and norepinephrine influence cognitive processes. Effects of acute stress are well documented for many cognitive processes, including memory, learning, and reward-related processing. In the domain of decision making, effects of acute stress on valuation, learning, and risk taking have been investigated with less consistent results. However, only very few studies so far used pharmacological approaches to specify the role of stress neuromodulators on decision making and these studies are hardly comparable due to differences in the experimental design, e.g., the decision making task used. Furthermore, the neural underpinnings of stress effects on decision making were uninvestigated. The aim of the project was to clarify the role of cortisol and norepinephrine, in their contribution to different processes related to decision making under risk. To this end, we aimed to combine precise pharmacological stimulation, behavioral modeling, and fMRI methods to systematically disentangle the effects of stress hormones on risk attitudes and loss aversion as well as their relation to neural correlates of processing subjective value and risk. Our research program comprised two studies: In study 1, we aimed to examine the role of single and combined noradrenergic and HPA axis activation on decision making under risk at the behavioral, computational, and neural level. In study 2, we aimed to use a similar approach to investigate the effects of noradrenergic blockade on decision making under risk. Recruitment of both studies is completed. In sum, we tested 247 healthy men in the two parts of the project and reached our a priori planned sample size. Data of study 2 are still to be analysed. In study 1, we conducted a double-blind, placebo-controlled, between-groups study design. Participants received 10 mg yohimbine and/or 10 mg hydrocortisone or placebo. In a first step, we analysed resting state fMRI data to investigate functional connectivity within of large scale neural networks. Salivary markers of both noradrenaline and cortisol were still significantly elevated at the time of resting state scanning, but we found no changes in within network connectivity of the three networks, both after single and combined drug administration. We also used seed-based analyses to compare Resting State Functional Connectivity (RSFC) of the amygdala and hippocampus separately between the four study groups. The group with elevated NE and cortisol showed significantly increased RSFC between the amygdala, hippocampus, and cerebellum compared to placebo. These three brain areas are involved in associative learning and emotional memory, suggesting a critical role for this network in the human stress response. Our results are in line with recent studies that have proposed a central role for the cerebellum in the neurofunctional stress response. We also investigated selective attention and used an emotional dot probe task before hydrocortisone and yohimbine administration. Selective attention was associated with cuneus activity but we did not find any differences between experimental treatment groups in selective attention and its neuronal activation. Data of the decision making task and study 2 has to be analysed in the future. Our first results replicated some finding from the literature but not all of our hypotheses could be confirmed. In addition to methodological issues and differences to other studies, our relatively large sample size might have prevent false positive effects.
