the study aims to explore whether there is an interaction between oxytocin and serotonin in the regulation of emotion-based behavior by using a between-subject randomized double blind pharmacological fMRI design during which 4 groups of healthy male subjects will receive combinations of oxytocin nasal-spray (versus placebo) and acute tryptophan depletion (ATD, versus placebo)

Convergent evidence from animal models and human studies suggests that both, serotonin and oxytocin are important regulators of social emotional behavior. Evidence is emerging that both systems interact in this domain. To determine the interaction of both systems on human social behavior, the present study aims to combine a randomized placebo-controlled administration of modulators of both systems (Oxytocin nasal-spray and acute tryptophan depletion, ATD) and their combination within a pharmaco-fMRI experiment. To determine effects on the neural networks engaged in social emotional processing, healthy male subjects will receive single doses of oxytocin (24IU) versus placebo and ATD (75.2g) versus placebo before fMRI measures of emotion perception and resting state will be acquired. To control for potential effects of pre-medication personality traits as well as effects of medicines on mood, subjects will be administered pre-treatment assessing relevant personality traits and post-treatment assessments of mood.

Inclusion Criteria:

• health subjects without past or current psychiatric or neurological disorders
• Right-handedness

Exclusion Criteria:

• History of head injury;
• Medical or psychiatric illness.
• High blood pressure, general cardio-vascular alterations
• History of drug or alcohol abuse or addiction.
• Allergy against medications or general strong allergies
• Sleep disorders.
• Visual or motor impairments