In vivo neurochemistry of the ventral striatum and social competition in Homo sapiens

Ventral striatal function and trait anxiety have been shown to influence reward-seeking behaviour and social competition in humans. Moreover, social status perceptions have been shown to modulate ventral striatal function. The neurochemical underpinnings of these associations have not been investigated in humans so far. Studies in rodents have previously shown that ventral striatal neurochemistry is associated with these concepts. In humans, objective and perceived social hierarchy position show some links to physical and mental health. Trait anxiety is understood as a predisposing factor underlying neuropsychiatric disorders and is associated with social anxiety. Fear and avoidance of social interactions, both inherent to environmental contexts of direct social competition, are hallmarks of social anxiety. Lost economic productivity due to anxiety and social status associated decrements in physical and mental health renders this scientific topic of high relevance to public health policies. Moving towards a deeper understanding of these associations might constitute an important part in ensuring public health. We combine proton magnetic resonance spectroscopy with personality profiling and an incentivised handgrip motivation task in a socially competitive context to investigate the neurochemical underpinnings of these associations in young adult men. We chose the occipital lobe as a control region. In addition, we have measured the salivary biomarkers cortisol, testosterone and alpha-amylase. We found that trait anxiety is negatively linked to taurine and positively to the excitation-inhibition balance. State anxiety was positively linked to lactate. The salivary biomarker alpha-amylase was found to be associated with both state anxiety and lactate. Social anxiety was positively linked to the excitation-inhibition balance. We also show links between reward-seeking task performance and ventral striatal glutamine, phosphorylethanolamine, GABA, choline, glutathione, myo-inositol, the excitation-inhibition balance and the ratio of glutamine to glutamate. These associations were observed in the ventral striatum but not the occipital lobe. Our methodological approach allowed us to gain a deeper understanding of the neuroscience underlying the links between ventral striatal function, anxiety and motivated behaviour. Thereby, we have extended the literature on the links between personality traits, social status and motivated behaviour in socially competitive contexts and the underlying neurobiology. These new findings pave the way for future experimental investigations to further elucidate the links between neurochemistry, mental health and socially competitive behaviour. A deep understanding of the neuroscience underlying personality traits and performance allow for effective interventions with the goal to ensure public health.