Facilitation of acquisition and retention in preweanling but not postweanling rats by the presence of familiar home-nest material

A sensory-enhanced context facilitates learning and multiple measures of unconditioned stimulus processing in the preweanling rat.

“…This context effect was special to infants, as target learning in adult animals did not similarly benefit from an enhanced environment. The facilitative influence of a novel context on trace conditioning in the infant is consistent with a previously demonstrated decrement in classically conditioned taste aversion learning in the 18-day-old rat when conditioned in the home as opposed to an unfamiliar environment (Infurna, Steinert, & Spear, 1979) , but differs from the beneficial effect of familiar home-nest odors on infant learning observed for a number of aversively motivated instrumental tasks (T-maze discrimination to escape shock, Misanin & Hinderliter, 1989; Smith, Miller, Wigal, & Spear, 1989; Smith & Spear, 1981; passive avoidance, Smith & Spear, 1978; active avoidance, Misanin, Lariviere, Turns, Turns, & Hinderliter, 1986) .…”

Behavioral characteristics of the offspring of adolescent rats

“…Early separation or isolation of pups from the nest during lactation impairs learning and memory functions, whereas a normal relationship between mother and pups in the nest stimulates learning and memory (23). Maternal behavior during the first 10 days of the offsprings life serves to program their hypothalamicpituitary-adrenal responses to stress.…”

“…Maternal behavior during the first 10 days of the offsprings life serves to program their hypothalamicpituitary-adrenal responses to stress. As adults, the offspring of mothers with a normal relationship with their pups showed reduced plasma adrenocorticotropic hormone and corticosterone responses to acute stress, increased hippocampal glucocorticoid receptor messenger RNA expression, enhanced glucocorticoid feedback sensitivity, and decreased levels of hypothalamic corticotropin-releasing hormone messenger RNA (23). It has also been reported that inhibition of the transport of maternal steroids through the feto-placental barrier can permanently program amygdala glucocorticoid receptor messenger RNA expression and anxiety-like behavior in the offspring (24).…”

How typical and atypical contexts influence infant behavior.

“…This idea has been supported most notably in the laboratories of Campbell (e-g., Randall & Campbell, 1976) and Spear (e.g., Smith & Spear, 1978). For example, the presence of home litter cues has been shown to enhance learning in aversive tasks, such as passive avoidance (Smith & Spear, 1978) and discrimination escape (Misanin & Hinderliter, 1989;Smith et al, 1989). Testing with conspecifics present can facilitate conditioned taste aversion (Smith & Spear, 1978 as well as decrease isolation-induced activity ) and vocalizations (Carden & Hofer, 1992).…”

“…This idea is epitomized by Bolles's (1970) classic article on avoidance learning in which he argued that the rapidity of learning and extent to which an organism learns an avoidance response depends on its species-specific defense reaction (SSDR) to the controlling events of the avoidance problem. Ideas about species-specific reactions (SSRs) have been extended by others to incorporate age-specific reactions (ASRs) as well (e.g., Collier & Bolles, 1980;Smith & Bogomolny, 1983;Smith, Miller, Wigal, & Spear, 1989;Spear, 1984;Stehouwer & Campbell, 1980;Takahashi, 1992). By approaching the study of developmental processes with the recognition that very different reactions might be elicited to the same environmental event and modified accordingly in animals of different ages, one is posed to tap capabilities that might not otherwise be observed.…”