Objective:To investigate the effects of the short-term enriched environment on the spatial learning capacity of middle-aged rats and to figure out if the effects are sex dependent.Methods:14-month old male and female Sprague-Dawley rats were randomly divided into enriched group and standard group.Enriched rats were reared in enriched environment and standard rats were reared in standard environment for 4 months prior to the assessment in Morris water maze.Results:Compared with the standard environment

enriched environment could only promote the spatial learning capacity of the middle-aged female rats.The spatial learning capacity of standard male rats was superior to that of the standard females;however

the spatial learning capacity of enriched male rats was equal to that of the enriched females.Conclusion:Short-term enriched environment remarkably improved the spatial learning capacity of middle-aged female rats.The spatial learning capacity of middle-aged male rats was better than female rats

but the plasticity of the brain function in middle-aged female rats may be better than that in male rats.The results in the present study provide an important theoretical basis for the future study that searches for behavioral strategy to postpone the progress of brain aging.