The primary aim of this study is to investigate whether intranasal oxytocin can modulate the real-time functional magnetic resonance imaging (rt-fMRI) neurofeedback training effects by facilitating the use of an interoceptive strategy.

A randomized, double-blind, placebo-controlled between-subject design is employed in this study. A total of 80 healthy male participants are recruited and randomly assigned to two groups (oxytocin-OT vs. placebo-PLC). Participants self-administer either intranasal spray of oxytocin or placebo (24 IU). Both groups receive continuous real-time neurofeedback from the left anterior insula. Comparisons between the two groups are conducted to determine whether OT facilitates the neurofeedback effects.

The neurofeedback training task consists of 4 training sessions with real-time feedback and 1 transfer session without feedback. Each session comprises 5 regulation blocks and 5 rest blocks. At the end of each block, participants are presented with pain-related images and asked to rate their level of pain empathy, which was used to determine the effects of neurofeedback training at the behavioral level. A heartbeat detection task is performed pre- and post-training to measure interoceptive accuracy changes induced by neurofeedback training. A functional localizer task (heartbeat counting task) before training was used to localise the anterior insula. Neurofeedback training effects at the neural level were measured by anterior insula activity during training. Personality traits of subjects are assessed using validated Chinese version questionnaires, including the Toronto Alexithymia Scale (TAS), Multidimensional Assessment of Interoceptive Awareness (MAIA), Bermond-Vorst Alexithymia Questionnaire (BVAQ), Interoceptive Confusion Questionnaire (ICQ), Beck Depression Inventory (BDI), State-Trait Anxiety Inventory (STAI), Autism Spectrum Quotient (ASQ), Interpersonal Reactivity Index (IRI), and Cognitive Flexibility Inventory (CFI). Participants are required to complete the Positive and Negative Affect Schedule (PANAS) once each before OT treatment, after OT treatment (before the neurofeedback training task), and after the neurofeedback training task to measure mood changes.

Inclusion Criteria:

• Healthy subjects without any past or present psychiatric or neurological disorders.

Exclusion Criteria:

• History of brain injury medical or mental illness.
• Contraindication to MRI scanning (e.g., metal implants, claustrophobia or other --conditions that make them inappropriate for MRI scanning).

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