Then drink a cup of coffee or 5! In this NPR article it seems that researchers have been studying the effect of caffeine on the brain. They basically gave caffeine water to mice, who over the course of the study showed improvement in their memory. The catch was they needed a certain amount, and that translated to humans, would mean 5 cups a day.
However, like any scientific research on animals, it does not necessarily mean it will work out that way in humans. There has been some promising studies, that show people who drink 3 to 5 cups, in their 40s and 50s led to a 65-70% decrease in getting Alzheimer’s in their 70s. Once again, correlation does not prove causation, and another plausible explanation is that these people who drink coffee have active lifestyles. The activity might be combating the disease.