The role of homecage environmental stimuli in the facilitation of shock‐motivated spatial discrimination learning in rat pups

Abstract

In three experiments we examined the role of homecage environmental stimuli on learning an aversively motivated spatial discrimination task in 11-day-old rats. Varying the presence and absence of nest shavings in the correct and incorrect arms of a T-maze in Experiment 1 revealed that nest shavings had both nondirective facilitation and approach-eliciting properties. Training the 11-day-old rats in the presence or absence of shavings over three daily sessions and comparing their performance on the third day of training with that of a maturation control in Experiment 2 indicated that there is a residual training effect of the approach-eliciting property of nest shavings on shock-escape behavior. In Experiment 3, using nest shavings either as an irrelevant stimulus or as a redundant relevant cue in an aversively motivated T-maze reversal task suggested that 11-day-old rats acquire the discrimination task using non-nest spatial or directional cues as well as those provided by nest shavings. Overall, these results suggest that nest shavings introduced into aversively motivated tasks create a learning environment comparable to that of appetitively motivated instrumental tasks utilizing suckling from an anesthetized dam as a reinforcer.

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) .…”