Neurobiology of parent-infant relationships in rodents and primates

Among all mammals, infants are born immature and require parental care for survival. Infants have an innate motivation to maintain proximity with their caregivers through a physical approach and signaling their needs, which is collectively called the attachment system. Infants' attachment behavior promotes caregivers' parental behavior. The present review introduces research on the mechanisms underlying human parental and attachment behavior using rodents and primates as animal models. Especially, a New World monkey, the common marmoset (Callithrix jacchus) is a promising primate model. Unusually for other non-human primates, marmosets share infant care with family members including the mother, father, and older siblings. Their parental and attachment behaviors show many similarities with those of humans. Additionally, we discuss atypical behaviors in artificially reared marmosets as a model of insufficient parenting in comparison to disorganized attachment and attachment disorders in humans. Therefore, the marmoset is an ideal animal model for revealing the brain mechanisms of parental and attachment behaviors.