Oromucosal Oxytocin and Vasopressin Modulation of Emotional Face Attention

The goal of this clinical trial is to learn how 24 IU oxytocin (OT) and 24 IU arginine vasopressin (AVP), administered through the oral mucosa, affect attention to emotional faces and related brain activity in healthy adults. The study will compare OT and AVP with a placebo (PLC). The main questions it aims to answer are: 1. Does oromucosally administered oxytocin produce a behavioral pattern of modulation of top-down and bottom-up attention to emotional faces that is qualitatively consistent with previously reported intranasal oxytocin effects, and how does this pattern compare with that produced by arginine vasopressin? 2. Do oromucosally administered oxytocin and arginine vasopressin modulate neural responses within predefined brain regions and networks involved in emotional salience, attentional control, and social information processing, and are these neural effects consistent with their behavioral effects? 3. Do oxytocin and arginine vasopressin show overlapping or distinct patterns of neural modulation across top-down and bottom-up attention and high and low attentional load conditions? Researchers will compare 24 IU OT and 24 IU AVP with a placebo to determine how these treatments influence emotional face attention and brain activity. Participants will: * Receive 24 IU OT, 24 IU AVP, or placebo via a lyophilized oromucosal lollipop * Allow the treatment to be absorbed through the oral mucosa for about 5 minutes * Provide blood samples before and after treatment to assess peripheral oxytocin and vasopressin levels * Complete emotional face attention tasks during fMRI scanning * Have response time, response accuracy, brain activity, and peripheral neuropeptide levels measured * Complete questionnaires assessing mood states and personality traits before treatment administration to control for potential confounding effects

Inclusion Criteria: * Healthy subjects without past or current psychiatric or neurological disorders * Normal or corrected-to-normal vision * Eligible for MRI scanning and willing to undergo blood sampling and study treatment administration * For naturally cycling female participants, willingness and ability to complete the experimental session within the predefined menstrual-cycle phase, determined using menstrual history and urinary luteinizing hormone (LH) testing * Willing to comply with study requirements regarding alcohol, caffeine, nicotine, medication use, and other pre-session restrictions Exclusion Criteria: * History of head injury or epilepsy or seizure disorders * Current or past major psychiatric, neurological, or serious medical illness that may affect participant safety or study outcomes * Current use of psychoactive medications, hormonal medications, or other medications that may substantially affect central nervous system or neuroendocrine function * Regular smoking or inability to comply with the required nicotine abstinence period before testing * Face recognition impairment or other visual-perceptual impairment that could interfere with performance of the emotional face tasks