A longitudinal investigation of the effects of experience on the behavior of aging mice.

The effects of differential experience over most of the adult lifespan of mice were examined utilizing longitudinal designs. Repeated experience with nest building was contrasted with one-time only experience at various age levels from 4 to 24 months of age. The results suggest that the presence or absence of repeated exposure to nest building opportunities affects stability of nest building, while open field activity remains stable regardless of experience and vitality declines regardless of experience. Because nest building at maturation is not influenced by prior experience, the effect of differential experience during the course of aging is not interpreted as a reflection of differential initial acquisition of the behavior. Rather, performance differences are interpreted as providing evidence for the differential maintenance of neural integrity of the underlying mediator for the behavior. The discrepancy among the patterns of change for nest building, open field activity, and performance on the tightrope test is interpreted as reflecting differences in the relative importance of deterioration of the underlying neural mediators in comparison with decreases in muscular strength and flexibility. Implications for design issues in animal research in aging are discussed.