Production of new cells in the rat dentate gyrus over the lifespan: relation to cognitive decline.

The identification of neurogenesis in the dentate gyrus of adult mammals has sparked much interest in a functional role for these new neurons in hippocampal-dependent cognition. The current investigation used a model of age-related cognitive decline in rodents to study the relationship between changes in markers of neurogenesis and hippocampal function. New cell production in the granule cell layer was progressively reduced across the lifespan of male Long Evans rats, with a 40% reduction at middle age (13 months) and a reduction in excess of 80% in advanced age (25 months), compared with young mature adults (7 months). These effects of aging were not, however, predictive of cognitive status. In particular, the pronounced decrease in new cell production during aging did not distinguish among rats that varied over a wide range of cognitive abilities.