Oxytocin, sex hormones and brain activity in facial expression processing: A sex-based systematic review

BACKGROUND: Receptors for oxytocin, testosterone, estrogen and progesterone exist in brain structures involved in emotional processing. Together, these hormones might play an important role in accounting for sex difference in face expression recognition, wherein females typically outperform males. However, existing literature often focus on an individual hormone or single-sex samples, with limited attention to sex-effects on the neural features during facial expression processing. Thus, the impact of oxytocin and sex hormones on brain activity during facial emotion processing remains poorly understood. This systematic review examined the influence of endogenous levels and exogenous administration of oxytocin, estradiol, progesterone, and testosterone on brain activity in males and females, assessed using functional magnetic resonance imaging (fMRI), during the processing of facial emotional expressions. METHODS: A systematic review was conducted by performing a search of PubMed, Scopus, Web of Science and PsycInfo, in December 2024, following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Included studies assessed the influence of endogenous or exogenous oxytocin and sex hormones on brain activity using fMRI during a task involving facial expressions of emotion in healthy adult males and females (pre-menopausal aged >18 yr). RESULTS & CONCLUSION: A total of 38 articles were included in this systematic review. Results suggest that oxytocin, testosterone and progesterone modulate brain activity during facial expression processing in both sexes -and in a sex-dependent manner for oxytocin-, particularly in the amygdala. The influence of estradiol and hormonal contraceptive is unclear and highlights a continued gap in the literature.