Plasma corticosterone fluctuations in an infant-learning paradigm

Social buffering of the stress response: diversity, mechanisms, and functions

Protracted or repeated activation of the hypothalamic-pituitary-adrenocortical (HPA) system is associated with a variety of physical and psychological pathologies. Studies dating back to the 1970s have documented many cases in which the presence of a social companion can moderate HPA responses to stressors. However, there also are many cases in which this "social buffering" of the HPA axis is not observed. An examination of the literature indicates that the nature of the relationship between individuals is crucial in determining whether or not social buffering of the HPA response will occur. Other factors that affect social buffering, either directly or by influencing the social relationship, include the social organization of the species, previous experience, gender, integration into a social unit, and the developmental stage at which individuals are examined. Current evidence suggests that social buffering involves mechanisms acting at more than one level of the CNS. It is suggested that, in addition to promoting health, social buffering may have evolved to direct the establishment of social relationships, and to facilitate developmental transitions in social interactions appropriate for different life stages.

The role of age-dependent behaviors in the retention of an approach-avoidance response in preweanling rats

The role of age-dependent responses in infantile amnesia was examined. Ten- and 15-day old rats were trained in an approach-mother, avoid-shock paradigm and tested for retention immediately and after a 1-day delay. Ten-day-old rats were also tested after 6 days. Half of all the pups received a shock reactivation treatment before the delayed retention tests and half did not. In comparison to immediate retention, performance declined after 1 day but was reinstated by reactivation. A similar reactivation effect was found on 10-day-old pups tested after 6 days except that a different age-specific response was substituted for the original behavior. These effects were not found in untrained controls. These data show that learning may be expressed differently when acquisition and retention are measured at different developmental stages, a pattern that may be mistaken for infantile amnesia.