Evolutionary-adaptive and nonadaptive causes of infant attack/desertion in mammals: Toward a systematic classification of child maltreatment

Parental brain through time: The origin and development of the neural circuit of mammalian parenting

This review consolidates current knowledge on mammalian parental care, focusing on its neural mechanisms, evolutionary origins, and derivatives. Neurobiological studies have identified specific neurons in the medial preoptic area as crucial for parental care. Unexpectedly, these neurons are characterized by the expression of molecules signaling satiety, such as calcitonin receptor and BRS3, and overlap with neurons involved in the reproductive behaviors of males but not females. A synthesis of comparative ecology and paleontology suggests an evolutionary scenario for mammalian parental care, possibly stemming from male-biased guarding of offspring in basal vertebrates. The terrestrial transition of tetrapods led to prolonged egg retention in females and the emergence of amniotes, skewing care toward females. The nocturnal adaptation of Mesozoic mammalian ancestors reinforced maternal care for lactation and thermal regulation via endothermy, potentially introducing metabolic gate control in parenting neurons. The established maternal care may have served as the precursor for paternal and cooperative care in mammals and also fostered the development of group living, which may have further contributed to the emergence of empathy and altruism. These evolution-informed working hypotheses require empirical validation, yet they offer promising avenues to investigate the neural underpinnings of mammalian social behaviors.

Association of severe maternal morbidity with bonding impairment and self-harm ideation: A multicenter prospective cohort study

BACKGROUND

Evidence on the association between severe maternal morbidity (SMM) and mother-infant bonding and self-harm ideation is limited. We aimed to examine these associations and the mediating effect of Neonatal Intensive Care Unit (NICU) admission at one-month postpartum.

METHODS

This multicenter, prospective cohort study was conducted in Japan (n = 5398). SMM included preeclampsia, eclampsia, severe postpartum hemorrhage, placental abruption, and a ruptured uterus. Lack of affection (LA) and Anger and Rejection (AR) were assessed using the Mother-Infant Bonding Scale (MIBS), and self-harm ideation was assessed using the 10th item of the Edinburgh Postnatal Depression Scale (EPDS). Linear and logistic regression models were used to examine the association between SMM and MIBS score and self-harm ideation. A structural equation model (SEM) was employed to examine the mediating effect of NICU admission on the association between SMM and mother-infant bonding and postpartum depressive symptoms.

RESULTS

Women with SMM had a 0.21 (95 % confidence interval [CI]: 0.03-0.40) point higher MIBS score and a decreasing trend in the risk of self-harm ideation (odds ratio 0.28, 95 % CI: 0.07-1.14) compared to those without SMM. SEM analysis revealed that SMM was associated with MIBS partially through NICU admission.

LIMITATIONS

EPDS scores during pregnancy could be an unmeasured confounder.

CONCLUSIONS

Women with SMM had higher MIBS scores, particularly on the LA subscale, which was partially mediated by NICU admission. Psychotherapy to support parent-infant relationships is necessary for women with SMM.

Dysfunctions of brain oxytocin signaling: Implications for poor mothering

Good mothering has profound impact on both the mother's and the young's well-being. Consequently, experiencing inadequate maternal care - or even neglect - in the first stages of life is a major risk factor for the development of psychiatric disorders, and even for poor parenting towards the future offspring. Thus, understanding the neurobiological basis of maternal neglect becomes crucial. Along with other neurotransmitters and neuropeptides, oxytocin (OXT) has long been known as one of the main modulators of maternal behavior. In rodents, disruptions of central OXT transmission have been associated with poor maternal responses, like impaired onset of nursing behaviors, and reduced care and defense of the pups. Importantly, such behavioral and molecular deficits can be transmitted through generations, creating a vicious circle of low-quality maternal behavior. Similarly, evidence from human studies shows that OXT signaling is defective in conditions of inadequate mothering and child neglect. On those premises, this review aims at providing a comprehensive overview of animal and human studies linking perturbed OXT transmission to poor maternal behavior. Considering the important fallouts of inadequate maternal responses, we believe that unraveling the alterations in OXT transmission might provide useful insights for a better understanding of maternal neglect and, ultimately, for future intervention approaches.

Calcitonin receptor signaling in the medial preoptic area enables risk-taking maternal care

Maternal mammals exhibit heightened motivation to care for offspring, but the underlying neuromolecular mechanisms have yet to be clarified. Here, we report that the calcitonin receptor (Calcr) and its ligand amylin are expressed in distinct neuronal populations in the medial preoptic area (MPOA) and are upregulated in mothers. Calcr+ MPOA neurons activated by parental care project to somatomotor and monoaminergic brainstem nuclei. Retrograde monosynaptic tracing reveals that significant modification of afferents to Calcr+ neurons occurs in mothers. Knockdown of either Calcr or amylin gene expression hampers risk-taking maternal care, and specific silencing of Calcr+ MPOA neurons inhibits nurturing behaviors, while pharmacogenetic activation prevents infanticide in virgin males. These data indicate that Calcr+ MPOA neurons are required for both maternal and allomaternal nurturing behaviors and that upregulation of amylin-Calcr signaling in the MPOA at least partially mediates risk-taking maternal care, possibly via modified connectomics of Calcr+ neurons postpartum.