Dietary restriction imposed throughout adulthood has been reported to result in substantially increased longevity in the rat. One objective of the proposed research is to determine whether this treatment concomitantly retards the appearance of certain indices of aging in the brain. A second objective is to determine whether dietary restriction imposed during the suckling period, a treatment which has been reported to produce long-lasting retardation of somatic growth, will also result in increased longevity and retarded brain aging. Three groups will be reared: 1) rats reared in large litters but fed ad lib. throughout adulthood; 2) rats reared in small litters but fed restricted amounts of food throughout adulthood; and 3) rats reared in small litters and fed ad lib. throughout adulthood. At 200, 500 and 800 days of age, habituation of the startle response, cortical and hippocampal EEG frequency characteristics and levels of lipofuscin accumulation in the brain will be measured. Aging-related changes in these indices will be compared with lifespan in the three groups to determine whether treatment effects on longevity and somatic growth are associated with alterations in indices of CNS aging.