Variability in medial prefrontal cortex responses to smiles in human infants is linked to genetic variation in the oxytocin system

Smiling plays a critical role in guiding behavior during social interactions from early in human ontogeny. The current study examined whether genetic variation in the oxytocin system is linked to individual differences in medial prefrontal cortex (mPFC) responses to smiles in human infants. Results show that genetic variation in CD38 (rs3796863), linked in prior work to variation in oxytocin release, is associated with enhanced mPFC responses when 7-month-old infants were viewing smiles, but not when viewing angry or fearful faces. These findings provide novel evidence that oxytocin-related genetic variability contributes to early-emerging differences in social brain function and support the view that variability in processing of affiliative signals is influenced by neurogenetic mechanisms from early in human ontogeny.