"This project asks ‘Do oxytocin and dopamine systems interact in the human brain?’. It will encompass an innovative, inter- disciplinary method combining established techniques in neuropharmacology, neuroimaging and genetics. It will use a mentalizing (social dilemma) task where it is hypothesized that the trust-eliciting reward value of mutual cooperation is coded by both dopaminergic and oxytocinergic actions in the striatum. Support for this comes from dopamine´s well-characterized role in reward learning and oxytocin’s recently found impact on affiliate and cooperative behavior and its neurocorrelates. As a way of assessing these systems, I will combine, for the first time, oxytocin and dopamine manipulations; as well as integrate information from natural genetic variability to further support my predictions. The underlying assumption is that acute changes in their striatal levels as well as chronic predispositions affecting their systems can influence striatal activation during social reward processing. (Chronic predispositions arising from environmental historical events and personality will also be taken into account.)There is robust evidence that interplay between the dopamine and the oxytocine systems is crucial for social cognition from animal studies, however this has not yet been investigated in humans. The question is paramount and timely as mental illness enigmas involving trust/paranoia, social avolition and anxiety or drug addiction are still unresolved and new oxytocinergic therapies are now being clinically trialed for autism and schizophrenia (and partially to complement dopaminergic ones, as in the case of the latter). The ultimate goal herein is to inform the rational design of treatments for these conditions by better understanding the biological underpinnings of human social cognition, in respect to trust and social behaviour."