Researchers at the University of South Florida studying Alzheimer-like symptoms in mice found that a daily dose of 500mg of caffeine reversed the memory problems the mice experienced. After two months on 500mg of caffeine a day, the memory-impaired mice performed as well on memory tests as normal mice.
However, in other experiments with normal mice, the researchers found that caffeine did not improve the memories of normal mice. According to USF researcher Gary Arendash,
This suggest that caffeine will not increase memory performance above normal levels. Rather, it appears to benefit those destined to develop Alzheimer’s disease.