Abstract
Early life environment influences the development of various aspects of social behavior, particularly during sensitive developmental periods. We studied how challenges in the early postnatal period or (early) adolescence affect pro-social behavior. To this end, we designed a lever-operated liberation task, to be able to measure motivation to liberate a trapped conspecific (by progressively increasing required lever pressing for door-opening). Liberation of the trapped rat resulted either in social contact or in liberation into a separate compartment. Additionally, a condition was tested in which both rats could freely move in two separate compartments and lever pressing resulted in social contact. When partners were not trapped, rats were more motivated to press the lever for opening the door than in either of the trapped configurations. Contrary to our expectations, the trapped configuration resulted in a reduced motivation to act. Early postnatal stress (24 h maternal deprivation on postnatal day 3) did not affect behavior in the liberation task. However, rearing rats from early adolescence onwards in complex housing conditions (Marlau cages) reduced the motivation to door opening, both in the trapped and freely moving conditions, while the motivation for a sucrose reward was not affected.
Highlights
It has been demonstrated that social behavior can be affected by previous experiences, especially during sensitive developmental periods such as the early postnatal period and adolescence (Marco et al, 2011; Sandi and Haller, 2015; Tzanoulinou and Sandi, 2016)
Early life adversity in the first 2 weeks after birth-by depriving pups of maternal care or providing pups with poor quality of maternal care—can negatively affect social behavior, this has not been as extensively studied compared to effects on cognition (Bonapersona et al, 2019)
To study the impact of both negative and positive early life environments on pro-social behavior in adulthood, we introduced two environmental manipulations: (1) manipulation of the early postnatal environment through 24 h maternal deprivation (MD) on postnatal day 3; and (2) manipulation of the adolescent environment through enriched complex housing (CH) from postnatal day 26 onwards, up and throughout testing in adulthood
Summary
It has been demonstrated that social behavior can be affected by previous experiences, especially during sensitive developmental periods such as the early postnatal period and (early) adolescence (Marco et al, 2011; Sandi and Haller, 2015; Tzanoulinou and Sandi, 2016). Early life adversity in the first 2 weeks after birth-by depriving pups of maternal care or providing pups with poor quality of maternal care—can negatively affect social behavior, this has not been as extensively studied compared to effects on cognition (Bonapersona et al, 2019). The period of adolescence is a period in rodents in which brain circuitry implied in social behavior is still in development (Fuhrmann et al, 2015; Casey et al, 2019). Studies applying this ‘‘enrichment’’ during the adolescence period report reduced anxiety and enhanced learning, memory, and social behavior later on (van Praag et al, 2000; Simpson and Kelly, 2011; Crofton et al, 2015). There is not much known about the impact of early life conditions, both negative and positive, on pro-social behavior
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