Neural Correlates of Hypothalamic-Pituitary-Adrenal Regulation of Mothers with Their Infants

Abstract

Neural correlates of stress regulation via the hypothalamic-pituitary-adrenal (HPA) axis have been identified, but little is known about how these apply to real-world interpersonal stress contexts such as mother-infant interaction. We extended stress regulation research by examining maternal neural activation to infant cry related to HPA regulation with their infants. Twenty-two primiparous mothers listened to the cry sounds of their own 18-month-old infant and an unfamiliar infant and a control sound during functional magnetic resonance imaging scanning. Salivary cortisol was collected at four timepoints in a separate session involving the Strange Situation stressor. Cortisol trajectories were modeled with hierarchical linear modeling, and trajectory terms were used to predict neural response to own infant cry. Mothers who showed less HPA reactivity-indexed by trajectory curvature rather than level-showed increased activation to the cry of their infant relative to control sound across limbic/paralimbic and prefrontal circuits. These included periaqueductal gray, right insula, and bilateral orbitofrontal cortex as well as anterior cingulate-medial prefrontal cortex. Activations overlapped to some extent with previous HPA regulation findings and converged more extensively with circuits identified in other maternal response paradigms. Maternal stress regulation involves both circuits found across stressor types (i.e., prefrontal) and areas unique to the mother-infant relationship (i.e., limbic/paralimbic). The shape of the HPA response trajectory of mothers was more important than the level of such response in defining stress-related neural correlates. Future research should consider dimensions of the stress context and of physiological trajectories to define stress-regulatory circuits.