Early-life caregiving experience shapes hippocampal function throughout adulthood

Abstract

A defining feature of mammalian life is the relationship shared between the infant and primary caregiver, most commonly the mother. This relationship forms the basis of the first social memory an infant develops and promotes survival via persistent caregiving and teaching that shapes a repertoire of behaviors offspring will draw from throughout adult life. The quality of care that an infant receives from the primary caregiver is diverse, both across species as well as within. Although many infants are reared in a nurturing environment with adequate access to caregiving, others develop under conditions in which access to care is greatly diminished, both in terms of quality and quantity. Impairments often include features of neglect, resource scarcity, increased agitation and aggression, and early weaning, to name a few. Mammals reared under these adverse conditions often undergo altered developmental trajectories. The studies presented in this dissertation investigate how early-life experience with the primary caregiver influences hippocampal function, and how this shapes the development of social memory and emotional regulation throughout the lifespan. These studies elucidate the earliest ages in which social memories are behaviorally detectable, the persistence and evolution of these memories throughout the lifespan, and how hippocampal microcircuitry supports retrieval of these memories long after offspring have been separated from their mothers and have matured into adulthood. Additional emphasis is placed on outcomes in animals that experience neglect and increased roughness of care in the first weeks of life. These studies identify how adverse early-life experiences can lead to altered emotional regulation in adulthood. This dissertation highlights the effects of early-life experience on hippocampal plasticity and function, and how these experiences shape a variety of potentially adaptive behaviors in adult mammals.