Practicing a new and challenging activity is a good bet for building and maintaining cognitive skills.

Your brain has the ability to learn and grow as you age — a process called brain plasticity — but for it to do so, you have to train it on a regular basis.

"Eventually, your cognitive skills will wane and thinking and memory will be more challenging, so you need to build up your reserve," says Dr. John N. Morris, director of social and health policy research at the Harvard-affiliated Institute for Aging Research. "Embracing a new activity that also forces you to think and learn and requires ongoing practice can be one of the best ways to keep the brain healthy."

Physical and mental game

Research has shown that regular physical exercise is one way to improve cognitive functions like memory recall, problem solving, concentration, and attention to detail. However, it is not clear if the physical aspect alone boosts your brain or if a combination of other factors — like the mental challenge of the activity, the frequency you do it, and the desire to improve — also contribute.

Take swimming, for example. It has obvious cardiovascular and muscle-building benefits, but also involves constant thinking, processing, and learning. You have to be mindful of your breathing rhythm and how to properly execute strokes and kicks. You also can measure your expertise in terms of endurance and speed, which motivates you to practice your skills to be a better swimmer.

A brain training activity doesn't always have to be exercise-related. Much research has found that creative outlets like painting and other art forms, learning an instrument, doing expressive or autobiographical writing, and learning a language also can improve cognitive function. A 2014 study in Gerontologist reviewed 31 studies that focused on how these specific endeavors affected older adults' mental skills and found that all of them improved several aspects of memory like recalling instructions and processing speed.

Do the right activity

No matter which new activity you choose, make sure it follows three guidelines in order to maximize brain training, according to Dr. Morris.

Challenging. You have to always challenge your brain in order for it to grow. This is why choosing a new activity is so beneficial. It engages your brain to learn something new and offers the chance to improve.

Not up for a new endeavor? Raise the bar for an existing activity. For instance, if you are a casual golfer, commit to increasing your ability and aim to lower your handicap or shoot a specific score. "You don't have the challenge of learning something new, but rather the challenge of increasing your skill set and knowledge," says Dr. Morris.

Complexity. A complex activity not only strikes a match of excitement, but forces your brain to work on specific thought processes like problem solving and creative thinking. A 2013 study in Psychological Science found that older adults ages 60 to 90 who did new and complex activities, such as digital photography or quilting, for an average of 16 hours per week for three months scored better on working and long-term memory tests than those who did more familiar activities like reading and doing crossword puzzles.

Practice. Practice makes permanent, and that goes for brain function, too. "You can't improve memory if you don't work at it," says Dr. Morris. "The more time you devote to engaging your brain, the more it benefits."