The neurochemistry of shyness: Serotonin-dopamine interactions in social anxiety
Severe shyness, or social anxiety disorder (SAD), is a serious public health concern. Socially anxious behavior has been tied to exaggerated activity in the brain’s fear network and serotonin dysfunction but also to aberrant activation patterns during reward processing dependent on dopamine neurotransmission. Understanding the interaction between serotonin and dopamine synthesis is crucially important for etiologic theories of social anxiety. With the focus on serotonin-dopamine interactions, this project aims at investigating neuroimaging markers of individuals with SAD in comparison to healthy controls. A total of 48 participants, of which 24 are controls, will be recruited. All will be assessed with [11C]5-HTP and [11C]L-dopa positron emission tomography (PET), probing serotonin and dopamine synthesis respectively. In addition, participants will be scanned with functional magnetic resonance imaging (fMRI) during experimental paradigms probing fear- and reward-related neural processing. Analyses of gray and white matter structural integrity, gene polymorphisms, leukocyte telomere length and telomerase activity will also be undertaken. Finally, the accuracy of brain parameter-based classification of anxious vs. nonanxious individuals will be tested using support vector machine learning. Thus, the project uses state-of-the art imaging methods and novel data analytic approaches to answer crucially important questions regarding the cause of socially anxious behavior.