Temporal variation in maternal behavioral transitions under limited nesting conditions across postpartum windows in rats: Implications for neurobehavioral development.

Early mother-infant interactions are crucial for neurobehavioral development, yet how maternal care timing and organization respond to environmental adversity remains unclear. In altricial species like rodents, maternal behavior involves dynamic transitions that provide sensory experiences to developing pups. In this study, we examined how these transitions are influenced by environmental disruptions based on the timing of exposure. Using the limited bedding and nesting (LBN) paradigm, we exposed rat mothers and pups to LBN during three early postpartum windows: postpartum days (PPD) 2-4, 5-6, and 7-9, to assess its effects on infant development. Maternal behavior was analyzed using inferential statistics and network analysis. We assessed offspring outcomes on postnatal days (PND) 13-14, including body weight, eye opening, home-nest odor preference, nipple attachment, and ultrasonic vocalizations (USVs). We included infant outcomes from our prior study in which dams were exposed to LBN from PPD 2-9, with previously reported alterations in maternal behavior. LBN exposure on PPD 2-4 and 5-6 significantly altered maternal behavior, with increased high crouch posture, reduced off-nest behavior, and altered caregiving transitions. Network analysis revealed time window-specific pattern structure alterations, with fewer transitions between active and passive behaviors in LBN dams. No notable changes occurred when LBN was applied during PPD 7-9. Despite alterations in maternal care, pup outcomes remained largely intact. Only the LBN 2-4 group showed reduced body weight, and only LBN 2-9 pups emitted more low-frequency USVs. These findings suggest that while maternal behavior is sensitive to early disruptions, pup outcomes may be differentially affected depending on the timing and duration of exposure. Analyzing caregiving dynamics may contribute to future studies exploring how early caregiving influences long-term neurobehavioral development.