By Lyl Tomlinson

14 May 2014 - 12:02

'Exercising mice perform better on memory tests.' Photo (c) Airwolfhound, licensed under CC BY-SA 2.0 and adapted from the original.
'Exercising mice perform better on memory tests.' Photo ©

Airwolfhound, licensed under CC BY-SA 2.0 and adapted from the original.

Lyl Tomlinson, the US winner of the science communication competition FameLab, explains why you should lace up your running shoes if you want to remember where you left your keys. Lyl will join the international finals in Cheltenham on 3-5 June 2014.

How can you improve your memory?

We’ve all struggled with memory lapses. Whether it’s forgetting people’s names, entering rooms with no recollection of what you wanted, or searching your house endlessly for keys that are in your pocket — it seems many of us could benefit from having a better memory.

Because these issues are common, it’s no surprise that many people search online to find help. The desire for memory improvement is likely to fuel the popular Google search ‘How do I improve my memory’. If you search for it, you’ll find a number of suggestions.

One popular search result is: ‘Brain training games’. A 2010 study tested more than 11,000 people for six weeks to see how improvements in brain training games translated to tasks outside the games that relied on similar mental processes. The results showed that brain training games are generally good at improving one thing — how well you perform in brain training games. Unfortunately, this study and many others have concluded that playing these sorts of brain training games doesn’t seem to be useful outside of the games themselves.

Exercise is more effective than word searches

Another popular search result is: ‘Exercise’. Considering that many people don’t associate brain with brawn, some may believe this to be another gimmick designed to support overall health. However, many studies find that aerobic exercise does improve memory. People who run, bike, walk briskly or participate in other aerobic activities show improved performances on memory tests after exercise.

Although investigations of single bouts of aerobic activity have been performed, a number of significant findings have involved people who exercise regularly (usually about three to four times a week for a few months). There are even some researchers who argue that aerobic exercise only improves memory in people who exercise routinely.

Why does exercising boost your memory?

So how might this work?

Some scientists think that the boost in memory from exercise involves a region in your brain close to your temples called the hippocampus. It’s an important memory area in the brain and plays a role in remembering different kinds of information, including personal moments such as your first kiss. Notice that new jar of pickles in your packed fridge? It’s also involved in helping you remember old objects, so you recognise new ones. Most importantly for some, it assists in the long morning search for keys, by helping you remember the location of items.

However, there are other brain areas associated with memory. Another reason researchers believe the hippocampus plays a role in the boost in memory from exercise is because it has stem cells.

Exercise increases the number of stem cells in the brain

Not long ago, it was discovered that there are stem cells inside the adult human hippocampus. Some stem cells have enormous potential. In fact, a number of controversial reports involve the stem cells found in embryos, which can become many different kinds of cells found in the body.

However, stem cells in the adult hippocampus will likely grow up to become a few types of specialised brain cells, like astrocytes, which can provide important nutrients to other cells, and neurons dedicated to memory.

The developing neurons act like memory chips, similar to the RAM (or random-access memory device) you would find in a personal computer or smart phone. They are thought to help us acquire and retrieve new memories more efficiently. Amazingly, aerobic exercise has been shown to increase the number of stem cells and newly born neurons found in the hippocampus in animals.

Though scientists believe this happens when people exercise regularly, they have yet to see the stem cells in action. Due to the limits of current technology and the stem cells’ small size, they are difficult to view in the brains of living humans. Studies that have directly identified them so far have been post-mortem.

Fit mice have more stem cells and memory-related neurons than couch potato mice

However, the field has attempted to close the gap by producing a number of conclusive experiments in adult mice (which are genetically similar to humans). The results from many experiments show that mice that run regularly have more stem cells and newly born neurons than mice that don’t. The exercising mice also perform better on memory tests.

Another important study went as far as looking into the brains of people who exercise, using magnetic resonance imaging (MRI) scans that assess the brain on a large scale. The results showed that people who demonstrated a boost in memory from exercise also had a specific increase in blood flow to the stem cell area of the hippocampus. Because brain areas that require more blood are more active, it’s thought that the increase in blood flow was likely caused by stem cell activity.

The link between exercise and memory could help stave off dementia

After all this discussion about the hows and whys of the memory boost from exercise, you might feel like I do about online music streaming and Lady Gaga songs — you don’t really care how it works, just as long as you get what you want.

Although understanding the inner workings of this process may not affect most people, it could help those with progressive memory conditions, such as those developing Alzheimer’s disease and other forms of dementia.

A number of studies have shown that elderly people who engage in aerobic activities, such as brisk walking sessions, are at lower risk of developing many forms of dementia including Alzheimer’s disease (though there is some debate about people with a genetic risk).

Another interesting fact that suggests stem cells play a role in memory and dementia is that older animals have less hippocampal stem cells. This coincides with a time when memory and cognition worsens.

Exercise may help prevent the loss of stem cells that help the brain remember things

Elderly mice, similar to elderly humans, also engage in aerobic exercise (running in wheels). Interestingly, although exercising elderly mice have fewer newly born neurons than younger mice, they have more than same-aged peers that don’t exercise, and perform better on memory tests. When experimenters terminate stem cells in other studies, it results in memory deficits. These results make scientists more confident that aerobic exercise helps prevent the loss of stem cells important for memory.

If researchers can figure out what exercise-related factors are causing stem cells to live longer, they may be able to use it as a preventative treatment for Alzheimer’s disease and other forms of dementia.

Scientists are still investigating the link between exercise and memory

Unfortunately, even though the stem cell explanation may seem obvious, it is just one of many possible causes.

Aerobic exercise has widespread effects and can influence many parts of the brain, including other memory-related areas. It is known to increase the activity of neurons, create new blood vessels (which provide nutrients to stem cells and mature brain cells) and boost chemicals important for forming memory-related connections between neurons. Some or all of these events could be behind the exercise-related memory boost.

At this point, trying to untangle the effects of exercise and rule out possibilities is as difficult as running a three-legged race. It will take more time and carefully designed experiments but considering the evidence for the stem cell related memory boost, it seems very promising.

While scientists are trying to figure it all out, you could go outside for a run. You’ll feel healthier and it just might save you hours searching for keys.

Lyl Tomlinson is a science-writing enthusiast originally from Bedford Stuyvesant in Brooklyn, New York. He is currently a PhD candidate in neuroscience at Stony Brook University. When not reading for his thesis, he writes for his personal blog at: The Science Stoop.

FameLab aims to discover charismatic, up-and-coming scientists who can inspire people to see the world from a new perspective. The competition is the brainchild of The Times Cheltenham Science Festival and is delivered by the British Council in 25 countries. NASA delivers the competition in the USA.

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