Erica R. Glasper

Editorial: Experience-Dependent Neuroplasticity Across the Lifespan: From Risk to Resilience

Individuals within monogamous species form bonds that may buffer against the negative effects of stress on physiology and behavior. In some species, involuntary termination of the mother-offspring bond results in increased symptoms of negative affect in the mother, suggesting that the parent-offspring bond may be equally as important as the pair bond. To our knowledge, the extent to which affect in paternal rodents is altered by involuntary termination of the father-offspring bond is currently unknown. Here, we investigated to what extent separation and paternal experience alters passive stress-coping behaviors and dendritic morphology in hippocampal subfields of California mice (Peromyscus californicus). Irrespective of paternal experience, separated mice displayed shorter latencies to the first bout of immobility, longer durations of immobility, and more bouts of immobility than control (non-separated) mice. This effect of separation was exacerbated by paternal experience in some measures of behavioral despair—separation from offspring further decreased the latency to immobility and increased bouts of immobility. In the dentate gyrus, separation reduced dendritic spine density regardless of paternal experience. Increased spine density was observed on CA1 basal, but not apical, dendrites following paternal experience. Regardless of offspring presence, fatherhood was associated with reduced apical dendritic spine density in area CA3 of the hippocampus. Separation enhanced complexity of both basal and apical dendrites in CA1, while fatherhood reduced dendritic complexity in this region. Our data suggest that forced dissolution of the pair bond induces passive stress-coping behaviors and contributes to region-specific alterations in hippocampal structure in California mouse males.

Our understanding of postpartum anxiety (PPA) in fathers is limited, despite the negative consequences of anxiety on the father and child. Offspring contact reduces PPA in mothers; however, parallel investigations in fathers has gone unaddressed. Adult neurogenesis in the dentate gyrus (DG) contributes to anxiety regulation and is altered during the postpartum period, yet the effects of fatherhood on the production, or survival, of newborn cells in the DG, and the role of adult neurogenesis in PPA regulation, have not been examined. Using the biparental California mouse (Peromyscus californicus), we examined the relationships among postnatal day, anxiety‐like behavior and adult neurogenesis in fathers. We hypothesized that attenuated anxiety‐like behavior and enhanced adult neurogenesis would be observed when father–offspring contact was increased. We observed a reduction in anxiety‐like behavior on the elevated plus‐maze, but only at PND 16, a time of peak pup retrieval. Fatherhood reduced 1‐week survival of newborn cells; however, surviving cells were maintained until 2 weeks postpartum. In contrast, non‐fathers experienced a significant reduction in the survival of newborn cells between 1 and 2 weeks postpartum. Fatherhood also increased the numbers of newborn cells that expressed a neuronal phenotype. Collectively, these findings suggest that offspring interaction contributes to reductions in anxiety‐like behavior and the maintenance of newborn neurons in the DG of fathers. These data contribute to our knowledge of the postpartum affective state in fathers, findings that may contribute to improved health of both the father and offspring.

Introduction: Parenting alters the hippocampus, an area of the brain that undergoes significant experience‐induced plasticity and contributes to emotional regulation. While the relationship between maternal care and hippocampal neuroplasticity has been characterized, the extent to which fatherhood alters the structure and function of the hippocampus is far less understood.Methods: Here, we investigated to what extent fatherhood altered anxiety regulation and dendritic morphology of the hippocampus using the highly paternal California mouse (Peromyscus californicus).Results: Fathers spent significantly more time on the open arms of the elevated plus maze, compared to non‐fathers. Total distance traveled in the EPM was not changed by paternal experience, which suggests that the increased time spent on the open arms of the maze indicates decreased anxiety‐like behavior. Fatherhood also increased dendritic spine density of granule cells in the dentate gyrus and basal dendrites of pyramidal cells in area CA1 of the hippocampus.Conclusions: These findings parallel those observed in maternal rodents, suggesting that the hippocampus of fathers and mothers respond similarly to offspring.