The effect of an enriched environment and cognitive maturity on long-term reactivation of object recognition memory in male Sprague-Dawley rats.

This study examined the effect of environment and cognitive maturity on longterm reactivation of recognition memory in rats. Forty male Sprague-Dawley rats were housed in either an enriched environment or standard conditions. Animals were tested in the Novel Object Recognition (NOR) task as either adults or periadolescents. Results showed exposure to an enriched environment significantly increased the ability of animals to discriminate between a novel and a familiar object. Results also revealed that the impact of environmental enrichment was significant in adults but not in periadolescents. Immunohistochemical staining for the immediate-early gene products c-Fos and zif268 was performed to examine the involvement of prefrontal cortex, hippocampus, and perirhinal cortex in the NOR task. Levels of c-Fos in the prefrontal cortex were significantly higher in adults. Significant inconsistencies were found among levels of both IEG products in the brains of periadolescents. The findings in the present study support the need for prefrontal cortical maturation in rats in order to discriminate between novel and familiar after a long delay