The interplay between emotional arousal and memory processes – from large-scale to translational fMRI studies

Emotional arousal greatly impacts what we remember about an event and how well we remember it. This memory-modulating effect of arousal has been subject to intensive research for decades. In recent years, fMRI data has enabled increasing understanding how arousal and memory are integrated in the human brain. Since then, researchers have been striving to identify the brain regions involved in emotional memory processing and to elucidate how dysfunctional activation in certain neuronal circuits relates to psychiatric disorders. However, the majority of fMRI studies lack sufficient statistical power to produce robust results. In addition, the common use of group-level analyses based on contrasts, a rather insensitive method compared to analysis on an individual level, has, up to now, hampered the utility of fMRI findings for clinical routine.
The aim of the present thesis is to present new scientific advances in the relationship between emotional arousal and memory documented in two publications that used large-scale fMRI data from our lab in two different ways. The publication Loos et al. (2019) took an exploratory approach based on fMRI and behavioral data from more than 1’000 healthy young subjects. Applying multi-voxel pattern analysis, we identified a brain network which could be used, on the one hand, to predict an individual’s perceived arousal during encoding and, on the other hand, to predict episodic memory performance of an individual during later recognition. Both processes, perceived arousal and episodic memory, are heavily impaired in emotional memory-related diseases like anxiety disorders. Therefore, the reported network constitutes an important target for further research in patients with dysfunctional emotional memory.
The second publication, Loos et al. (submitted), used large-scale data to derive a hypothesis-driven research question which we tested in an independent fMRI study. Using a pictorial working memory (WM) task in subjects reporting fear of snakes, we could demonstrate that high compared to low WM load not only acutely decreased amygdala activity but also reduced perceived phobic fear and disgust towards snake pictures. Additional effective connectivity analysis revealed that the dlPFC, which is particularly engaged in WM tasks, exerted an inhibitory influence on the amygdala during high WM load conditions. The study intended to translate findings from basic research into a more clinical context and may inspire the development of new approaches for the treatment of anxiety disorders.
In sum, the thesis adds to the knowledge on the interplay between emotional arousal and episodic as well as working memory processes by providing robust and reproducible results. In addition, it highlights the importance of well-powered fMRI studies for the identification of neural mechanisms that improve diagnosis and treatment in clinical practice.