Memory is a strange thing. When you take in sights, sounds, touch, and smell, they're converted to memory in your hippocampus, the seahorse-shaped part of your brain's temporal lobe. After it passes this seahorse gatekeeper, a memory is broken into its sensory components and zapped to different parts of the brain. Then, when you want to recall that memory again, all the pieces are reassembled. Gee, that seems like an awful lot to go through just to remember to buy milk on the way home.

As incredible as the inner workings of memory are, there can be wrenches thrown into the system. Here are five such memory thieves.

The remote control. Physical activity is good for your mental capabilities, according to University of Illinois research. And you don't even have to hit the gym to boost your brain. Just walking an hour twice a week is enough to increase memory.

A lone-wolf attitude. Isolating yourself may be a way to get some peace. In fact, it may be so quiet, you can hear your brain function oozing away. Lack of socialization makes you more apt to lose memory. The opposite is also true: Those with the highest level of social integration had the slowest rate of memory decline, according to Harvard researchers. It's likely that when you're around others, your brain is stimulated from the conversation and social interaction.

Poor sleep. Every once in a while, you need to turn off your computer to clear its digital memory. Then, presto, when you turn it back on, it's all better. Your memory works in a similar way. Sleep allows your brain to sort of clear your cache of excess memory baggage and allow you to recall the important information you learned in the previous day. Also, if you're always tired from not getting enough quality sleep, it's hard for your brain to process new information. Shoot for eight hours, and get more restful sleep by turning your clock away from you so you can't see its lights.

The blues. When you're down, you're less likely to be attentive and attuned to new information. In fact, folks who are often depressed or stressed are 40 percent more likely to develop memory problems than those with sunnier outlooks. Depression also floods the body with stress hormones that can damage areas of the brain responsible for memory.

Testosterone. If your body's natural balance of this hormone is out of whack, you might not be able to remember who won the National League batting title in 1967. However, researchers are still trying to pin down whether too much or too little testosterone causes the memory lapses. (Pssst—it was Roberto Clemente.)