Environmental influences on cognitive decline in aged rats

Two experiments are reported in which young and old rats, housed in an impo verished (IE), enriched, (EE), or standard (SE), environment, were tested o n a series of complex, blind-alley mazes. In Experiment 1, 3-months exposur e to IE exacerbated age differences in maze performance, relative to the di fferences between young and old rats in EE and SE. Old rats in the EE and S E conditions did nor differ from each other. In Experiment 2, rats were rai sed for an additional ? months in tither IE or EE before further maze testi ng. The main findings were that the maze performance of old rats, transferr ed from IE to EE, improved significantly, whereas the performance of old ra ts, transferred from SE or EE to IE, declined. These results indicated that the: deleterious effects of an impoverished environment on learning and me mory are, at least partly, reversible, and that experience in a stimulating environment can protect old rats from the adverse effects of relocation to a deprived environment. Taken together, the results highlight the impact o f environmental influences on cognitive function in old age, and emphasize the need to consider nonbiological factors in understanding the process of aging. (C) 1999 Elsevier Science Inc.