A translational study of game-theoretic models of social exchanges: serotonin and vulnerability to depression

Social isolation is known to be a risk factor for medical problems including depression. We also know that the process of recovering from depression is often accompanied by greater involvement with family, friends, and wider social groups. In this project, we will use a variety of techniques including functional brain imaging, pharmacology and game-theory to examine the brain mechanisms that allow people to establish stable patterns of reciprocally cooperative behaviour with a variety of social partners. We will investigate the role of a brain chemical called serotonin (which is important in depression) in learning socially supportive relationships. We will also test whether individuals who are at risk for recurring depression show problems in these forms of social learning. The results will help us link biological mechanisms underlying depression to the problems in social function that increase peoples risk of developing the disorder.

Social isolation is a significant risk factor for the onset and maintenance of psychiatric illness particularly major depressive disorder (MDD). Conversely, recovery seems often to go along with increased contact with socially supportive networks and an increased value placed upon interactions with individuals within this network. Despite the acknowledged importance of impoverished social exchanges in MDD, there has been little research linking what we know about the neurobiology of the disorder to the social isolation that confers risk for MDD and is exacerbated by the onset of the illness. However, experimental research with animal models suggests that alterations in serotonin neurotransmission can have important effects on social behaviour. We, therefore, propose to use a combination of neuropsychology, pharmacology and functional brain imaging (fMRI) to investigate the role of serotonin in the performance of game-theoretic models of social exchanges as a way of understanding the biological processes that impair social interactions in MDD. Our overarching hypothesis is that serotonin plays a particular role in learning about the reward value of cooperative behaviour, both in the context of dyadic interactions with identified social partners and as part of larger social groups, and that serotonergic dysfunction in individuals with a history of MDD interferes with the development of supportive patterns of social relationships that might help protect against illness relapse.