Oxytocin's impact on the social brain: Individual differences and context shape a core amygdala-mediated mechanism

Research on the effects of intranasal oxytocin (IN-OXT) on social behavior has often yielded contradictory results, likely due to variability in sample characteristics and research methodologies. To understand oxytocin's influence on neurophysiology and the associated social behaviors, this review synthesizes findings from the past decade on oxytocin's impact on brain physiology, mainly measured by functional magnetic resonance imaging (fMRI) Blood Oxygenation Level Dependent (BOLD) signals. This includes studies on resting-state connectivity, task-based functional connectivity during social cognition tasks.

Following the PRISMA guidelines, we reviewed 27 studies sourced from Embase, Medline, and APA PsycINFO. Key characteristics of each study were summarized, including sample size, subject demographics, oxytocin dosage and administration duration, BOLD signal processing and analytical methods, social behavior assessments, and the primary fMRI and behavioral outcomes related to oxytocin's effects.

During resting-state, IN-OXT predominantly modulates the amygdala, precuneus and insula, influencing the functional organization of large- scale networks such as the default mode network and the salience network. Task-based fMRI studies revealed that oxytocin exerted stress-regulatory and context- dependent neurobehavioral effects through amygdala-centered activity, with direction and magnitude varying according to individual traits, sex, and dosage.

We further discussed factors that influence IN-OXT's effects on social behaviours. Future research should integrate molecular and neuromodulatory techniques, recruit more diverse samples, and employ ecologically valid paradigms such as hyperscanning to capture real-world social interaction dynamics.