The main goal of this study is to investigate the modulatory effects of intranasally administrated oxytocin on the processing of emotional stimuli and its acting routes.

In recent years ample studies have reported that intranasally administered oxytocin (OT) can facilitate social motivation and cognition in healthy and clinical populations. However, it is still unclear how effects are mediated since intranasally administered OT can both directly enter the brain (nose to brain) and increase peripheral vascular concentrations (nose to blood). The relative functional contributions of these routes are not established and have received insufficient attention in the field. Therefore, the investigators use the vasoconstrictor (VC) pretreatment to prevent intranasal OT (24 IU) from increasing peripheral concentrations and combine fMRI, behavioral measures, with physiological recording to examine the modulatory effects of OT on implicit emotional processing and its acting routes. In total 120 male participants are recruited for this double-blind, between-subject, placebo-controlled study. After arriving at the laboratory, participants first completed questionnaires for about 30 minutes, and were then randomly assigned into 3 groups receiving intranasal administration of "VC + OT", "placebo (PLC) + OT", or "VC + PLC". Then, they complete a resting-state scan and two task-based scans lasting approximately 65 minutes in total. There is a sencond resting-state scan between two task-based scans, which is mainly used as a break between the two tasks. Blood samples are collected twice (after finishing questionnaires and 30 minutes post-treatment) for subsequent analyses of plasma OT concentrations. The two task-based scans consist of an implicit face-emotion processing task (gender judgments of faces) and an emotional scene processing task (judging whether a child/old people/building/dog is present in the picture). After scanning, there is a 40-minute picture rating task (emotional valence, intensity, and arousal). Questionnaires include State-Trait Anxiety Inventory, Beck Depression Inventory II, Liebowitz Social Anxiety Scale, Autism Spectrum Quotient, Social Responsiveness Scale-2, Interpersonal Reactivity Index, Childhood Trauma Questionnaire, Toronto Alexithymia Scale and Positive and Negative Affect Schedule.

Inclusion Criteria:

• Healthy subjects without past or current psychiatric or neurological disorders

Exclusion Criteria:

• History of head injury.
• Medical or psychiatric illness.
• Subjects take a certain drug for a long period of time.
• Subjects have metal implants in their bodies.

Individuals whose self-identified gender is consistent with their biological sex.