Woman Placing Sticky Notes on Board
Credit: Compassionate Eye Foundation/Getty Images

As we grow older, we tend to become just a bit more forgetful. (Seriously, how many among you lost your keys this week or forgot where you parked your car in the mall?) But, there are more than a few ways you can keep your brain sharp well into your elder years. Here are a few scientifically-backed brain training exercises you can do just about anywhere and anytime to stay mentally sharp.

Draw a map

As Reader's Digest noted, cab drivers in London are required to memorize more than 25,000 streets across the city. And, because of this extraordinary task, neurologists at the University of London found that these drivers have significantly larger hippocampi, which is the region of the brain responsible for memory storage.

"We conclude that specific, enduring, structural brain changes in adult humans can be induced by biologically relevant behaviors engaging higher cognitive functions such as spatial memory, with significance for the "nature versus nurture" debate."

The best way to practice this behavior? Try memorizing the streets in your own hometown and draw a physical map of your neighborhood to see how many streets you can name.

Practice some old-school math problems

Look, math was far from our best subject either, but it's key to keep practicing those problems well into adulthood. And this time, it should be less stressful because nobody is grading you.

According to Ryuta Kawashima of Tohoku University, simple mathematical problems using addition and subtraction can boost activity levels in both left and right hemispheres of the frontal lobe.

"Anyone who has exercised knows that if you want to make a muscle stronger you have to subject it to strain, to push it beyond its comfort level. The brain is no different," Keith Devlin, executive director at the center for the study of language and information at Stanford University, California, and author of The Maths Gene, shared with The Guardian. Try these math Mind Games to get you started.

Share a story with friends

Storytelling may be one of the best ways to boost cognitive function in later years, according to researchers at the University of Missouri.

In one study, the group used TimeSlips, a "nationally recognized storytelling program for people with dementia" that encourages people to use their imaginations to create short stories, rather than factual recall.

"TimeSlips provides rich, engaging opportunities for persons with dementia to interact with others while exercising their individual strengths," Lorraine Phillips, assistant professor in the Sinclair School of Nursing, said in a statement. "It encourages participants to be actively involved and to experience moments of recognition, creation and celebration. Meaningful activities, such as TimeSlips, promote positive social environments that are central to person-centered care."

WATCH: Study Shows The Best Kinds of Friends Are The "Mean" Ones

Using the program, the researchers found that participants had increased expressions of pleasure and initiation of social communication. The effect lasted several weeks following the final session.

Take a foreign language class

Learning a new skill, like a new language, can do wonders for your long-term brain health. Several studies show that learning something new stretched out over a long period of time can protect an aging brain. And what better thing to learn than a new language, as it can also protect against late onset dementia.

"Our results suggest a protective effect of bilingualism against age‐related cognitive decline," research published in the Annals of Neurology wrote. "The effects are not explained by other variables, such as gender, socioeconomic status, or immigration. Importantly, we detected no negative effects of bilingualism. The cognitive effects of bilingualism showed a consistent pattern, affecting reading, verbal fluency, and general intelligence to a higher degree than memory, reasoning, and speed of processing."

Enroll in a class near you, or better yet, download an app like DuoLingo so you can practice anywhere.

Download a brain training app

Perhaps one of the easiest ways to protect your brain and boost your memory is to download a brain training app. But, be warned: Not all apps are created equal. According to an Australian study of the many brain training apps available to consumers, just BrainHQ and its competitor Cognifit have actual cognitive benefits. This, Fast Company wrote, is because both apps are focused on improving your brain's processing speed.

"You see an image in the center of your vision–for example, either a car or a truck–and at the same time, you see another image way off in your peripheral vision. The images are only on the screen for a brief period of time–well under a second," Dr. Henry Mahncke, CEO of Posit Science, shared with Fast Company. "You then have to say whether you saw the car or the truck in the center of your vision, and then you have to show where you saw the image in your peripheral vision. This challenges the speed and the accuracy of your visual system. And as you get faster and more accurate, the speed increases and the peripheral vision task gets more demanding–pushing your brain further."

Download the apps today and see for yourself just how much more you can remember tomorrow. Now, if only I could find my damn keys…