Effects of successive environments on brain measures

Abstract

To test the persistence of cerebral effects induced by differential experience, littermate rats were placed in an enriched environment (EC) or an impoverished environment (IC) for either 30 or 80 days. Following this initial period, one rat of each litter was transferred from the EC to IC condition while its littermates remained in EC or IC. The second phase lasted either 7, 14, 21, 32 or 47 days. The cerebral differences induced by differential experience began to dissipate when the animals were placed in a common environment, but statistically significant differences still persisted weeks after the end of the inducing conditions. Greater persistence was found after 80 days of initial exposure than after 30 days. Following 80 days in EC, significant persistence of brain weight differences was found 21 days after removal from EC to IC; significant persistence of differences in acetylcholinesterase and cholinesterase activities were found 47 days later. Different brain regions and different measures showed somewhat different patterns of results. Three different kinds of environmental enrichment — devised in three laboratories — were compared for their effects on brain weights and brain enzymes.