Erratic Maternal Care Induces Avoidant-Like Attachment Deficits in a Mouse Model of Early Life Adversity

Attachment theory offers an important clinical framework for understanding and treating negative effects of early life adversity. Attachment styles emerge during critical periods of development in response to caregivers ability to consistently meet their offsprings needs. Attachment styles are classified as secure or insecure (anxious, avoidant, or disorganized), with rates of insecure attachment rising in high-risk populations and correlating with a plethora of negative health outcomes throughout life. Despite its importance, little is known about the neural basis of attachment. Work in rats has demonstrated that limited bedding and nesting (LB) impairs maternal care and produces abnormal maternal attachment linked to increased pup corticosterone. However, the effects of LB on attachment-like behavior have not been investigated in mice where additional genetic and molecular tools are available. Furthermore, no group has utilized home-cage monitoring to link abnormal maternal care with deficits in attachment-like behavior. Using home-cage monitoring, we confirmed a robust increase in maternal fragmentation among LB dams. Abnormal maternal care was correlated with elevated corticosterone levels on post-natal day seven (P7) and a stunted growth trajectory that persisted later in life. LB did not alter maternal buffering at P8 or maternal preference at P18, indicating that certain attachment-like behaviors remain unaffected despite exposure to high levels of erratic maternal care. However, LB pups vocalized less in response to maternal separation at P8, did not readily approach their dam at P13, and exhibited higher anxiety-like behavior at P18, suggesting that LB induces avoidant-like attachment deficits in mice. Significance StatementThe impoverished conditions of limited bedding and nesting (LB) cause erratic maternal care and elevated corticosterone levels in rat and mouse pups. The increase in corticosterone levels causes attachment-like deficits in rat pups; however, it remains unclear whether similar deficits are observed in mice, where additional genomic and molecular tools are available. Using continuous home-cage monitoring, we confirmed a substantial increase in erratic maternal care and elevated corticosterone levels in 7-day-old mouse pups. LB mouse pups exhibited attachment-like deficits in some, but not all, tests, underscoring the robustness of this evolutionarily conserved bond. Despite some similarities, the attachment abnormalities observed in mice differed from previous reports in rats, paving the way for in-depth mechanistic studies in mice.