A: Beside teaching meditation, I'm a programmer who has written code for 37 years. I think my ability to interprete patterns and express logical procedures is as sharp now at age 55 as it ever was. I have a high standard for mental acuity and I share your concern of maintaining it.

Every programmer knows there is a tradeoff between processing time and memory consumption. You want to conserve your memory, so you'll want to emphasize mental processing, like logic and pattern matching. You want to avoid those mental exercises that require the accumulation of more facts. Crossword puzzles, for example, require a huge vocabulary and the continual accumulation of more words. Trivia games are memory hogs. Assembling jigsaw puzzles from pieces is better, for it doesn't use facts or language and yet the pattern matching skill of the brain is exercised. It uses only very short-term memory of shapes, which is reused for later puzzles. Card games are similar in that they use the pattern matching skill of the brain without requiring memory for many new facts. When reading the news, put more attention on seeing patterns and interpreting the context of events than on the facts.

A second tradeoff is between logical processing and input/output (I/O) processing. Most of our mental cycles are used for internal, logical processing: perhaps 80% of our mental capacity is used this way. The rest is used for handling I/O: processing our sensations. You not only want to keep your mind sharp; you want to exercise your attention to sensation.

For meditators, there is an even better solution to the problem of how to exercise the mind without filling up the available memory with more facts, and without encouraging internal fantasy. Concentration on sensation will train your mind to be attentive and discriminating, alert and aware of your world and yourself. There are at least two internal sensations that go on continually and that you can perceive clearly, with practice: your breathing and your heartbeat. There are additional benefits of concentration on these two particular sensations. The awareness of your heartbeat will tune you to heart-centered attitudes and behaviors, and the awareness of your breath will open the communication between your conscious and unconscious mind.

There is a difference between knowledge and wisdom, and what you want to accumulate in your life is wisdom, not more factual knowledge. Wisdom requires discernment, the ability to discard the unimportant and to see the pattern in the facts. Albert Einstein didn't even remember his own phone number. He said it was in the book, so it would be a waste of his mind to remember it.