You might consider trying (use carefully and you should double check with your doctor first ) an over the counter product called PS 100.
You can buy it at the health food store and some on-line vitamin stores like iherb website. They say in Europe, people take it for ADD and for minor memory issues. Check out what people are saying about it at the iherb website reviews....it is really interesting. Many people say it helps their memory a lot. (The ingredient that helps memory is Phosphatidylserine and again, it is sold in health food stores).

Also, avoiding excessive stress, taking a multi vitamin, doing crosswords (or similar challenging games) and regular exercise are all probably helpful and supportive.