Effects of multisensory environmental stimulation on contextual conditioning in the developing rat

The effect of increased exposure to multisensory stimulation during develop ment on conditioned freezing to contextual cues in preweanling Sprague-Dawl ey rats was examined. Rats given increased environmental stimulation exhibi ted long-term contextual conditioning at a younger age than rats that did n ot receive such stimulation when there was either low or moderate levels of conditioning (Experiments 1 and 2). These differences in contextual condit ioning were not a result of the stimulated rats reacting differently to sho ck (Experiment 4) or merely freezing more than the nonstimulated rats in al l situations (Experiment 3). The role of the glucocorticoid system in the e nhanced contextual learning of stimulated preweanling rats and the advantag es of the contextual conditioning procedure for studying the effects of env ironmental stimulation are discussed. (C) 2000 Academic Press.