The phrase "use it or lose it" applies to more than just the muscles in our bodies -- it applies to the neural pathways and connections in our brains. There are daily exercises and activities that can successfully work each of the brain's five major cognitive functions: memory, attention, language, visual-spatial skills and executive function. Here's an exercise for each part of the brain:

1. Memory: To maintain a good memory, you need to train for it. Listening to music is not only enjoyable, but by choosing a song you don't know and memorizing the lyrics, you boost the level of acetylcholine, the chemical that helps build your brain. Challenge yourself even more by showering or getting dressed in the dark, or using your opposite hand to brush your teeth. These challenges help build new associations between different neural connections of the brain.

2. Attention: We can improve our attention by simply changing our routines. Change your route to work or reorganize your desk -- both will force your brain to wake up and pay attention again. Combining activities such as listening to an audio book while jogging or doing math in your head as you drive forces your brain to work at doing more in the same amount of time.

3. Language: With regular practice, you can expand your knowledge of new words and retrieve them (and familiar words, too) faster. For example, if you usually only read the sports section of your newspaper, try reading a few business articles. You'll see new words, which are easier to understand when read in context, or easier to look up on a dictionary site if you are reading online.

4. Visual-Spatial: Analyzing visual information is necessary to be able to act within your environment. To work this cognitive function, try walking into a room and picking out five items and their locations. When you exit, try to recall all five items and where they were. Too easy? Wait two hours, then try to recall them again. Or do this exercise: Look straight ahead and note everything you can see both in front of you and in your peripheral vision. Challenge yourself to recall everything and write it down. This will force you to use your memory and train your brain to focus.

5. Executive Function: You use your logic and reasoning skills daily to make decisions, build up hypotheses and consider the consequences of your actions. Engaging in a brief visit with a friend boosts your intellectual performance by requiring you to consider possible responses and desired outcomes. Video games also require strategy and problem-solving to reach a desired outcome -- such as making it to the final level.

As we age, it's important to flex our mental muscles as well as our physiques. Now that you're aware of the five main cognitive functions and how to exercise them, it will be easy to find daily activities that will help you break a mental sweat and keep your brain in shape.

Neurologist and neuropsychologist Dr. Bernard Croisile is author of "Dental Floss for the Mind," "Get your Brain in the Fast Lane" and "Broccoli for the Brain," as well as developer of the HAPPYneuron online brain fitness program (www.happy-neuron.com).