The Real Happy Pill Page 12

  One year later, the members of the group who trained had become fitter, in contrast to the other group’s members who had performed the gentler exercises. Nothing surprising so far, but what had happened to the hippocampus? The hippocampi in people who had done the soft exercises had shrunk by 1.4 percent, which was no surprise either, since the hippocampus does shrink by about 1 percent each year after all.

  What was very interesting was that the hippocampus didn’t shrink at all in the members of the group that had endurance-trained; in fact, it had grown and become larger by 2 percent. Instead of aging by one year, the hippocampus had rejuvenated itself and size-wise had become two years younger! And that’s not all: the fitter the test subjects had gotten, the larger their hippocampi had grown. Among those who had seen the greatest improvement in their fitness, the hippocampus had grown by more than 2 percent.

  Of course, this raises the very important question of how this happened. One not unreasonable hypothesis is that the brain’s fertilizer, BDNF (which increases as we become more physically active), played a role. Perhaps you remember from the chapter The real happy pill that BDNF can strengthen the bond between brain cells and can therefore influence how well we remember things. And quite rightly so: when the scientists examined the levels of BDNF, they noticed that the more they had increased, the more the hippocampus had grown.

  What miraculous training program could revitalize and promote regrowth of such an important part of the brain in a single year? Did the test subjects pedal away on stationary bikes like bats out of hell, or did they run at draconian intervals? Not at all. The truth is that they neither biked nor ran. The only exercise they engaged in was a forty-minute power walk, three times a week. This means that you can stop, and perhaps even reverse, your brain’s aging and strengthen your memory by power walking or running a few times a week!

  However, it’s always better to be cautious in drawing conclusions when reading about these kinds of tests. Experiments are one thing, reality is another. If the hippocampus can be protected from aging, or even rejuvenated and grown bigger, what does that mean for us in life? Do we truly see improvement in our memory just by being physically active? The short answer is: Yes, absolutely!

  A long history of past tests points very clearly in the same direction: both short- and long-term memory are improved through exercise, and the gradual breakdown of the hippocampus that goes with aging can be slowed down, and even reversed.

  Genetic rejuvenation of the brain

  As if it weren’t enough that exercise safeguards the hippocampus from age-related shrinkage, it appears that it also offers protection against genetic aging. Just like other cells in the brain and the body, the hippocampus contains our genetic material. Our entire DNA and all our genes can be found in every brain cell. Normally genes don’t change during our lifetime, but our use of them changes, which can cause the body’s organs, including the brain, to age.

  If we examine the hippocampus brain cells of mice at different ages, we’ll find that in one group of genes the changes follow the animals’ aging. Among other things, these genes control the growth of brain cells and their ability to create connections to one another. As the mice age, the genes become less active, and this gradual genetic change doesn’t just make the hippocampus age—it also makes the entire brain grow older.

  However, not even cells’ aging at the genetic level means that we’re doomed with no recourse. When the test animals are allowed to run on a treadmill, something happens that can only be described as a miracle. Many of the genes that are adversely affected by aging are also influenced by training—in a positive way. Through mechanisms that are not yet fully understood, the hippocampus cells appear to become genetically younger after the test animals have run.

  These effects are powerful, but not instantaneous. The mice ran daily for eight weeks, which for us would be the equivalent of exercising regularly for several years—this means that the occasional jog is not enough. But intriguingly, it seems that those who are patient and who remain physically active regularly over a long time not only grow a larger hippocampus, but are also rewarded with revitalized hippocampus cells.

  PRACTICAL MEMORY TRAINING

  How do we go about strengthening memory with physical activity? Do we need to keep at it for several months, or do we notice any effects right away? Does it work best before learning something, or is it better to exercise after learning?

  You don’t have to work very long in the beginning to notice an effect. It has been shown that three months of regular endurance training leads to significant improvement in the ability to recall words. And it’s worth putting in the effort, because how much better your memory gets (i.e., the number of words you remember) is connected to how much fitter you become. Those who improved their fitness the most also saw the most benefit to their memory. This link is especially interesting, considering that the hippocampus grows larger as we get fitter.

  Do you think that three months is a long time? Don’t worry, you’ll notice results faster than that. Healthy individuals who biked regularly on stationary bikes were compared to a group of people of similar ages who did not cycle. Before the test began, the cyclists and noncyclists had comparable results on several different memory tests. However, the cyclists soon pulled ahead in both fitness and memory. Six weeks in, it was obvious that the group that cycled were better at the memory tests, and the differences became more substantial the longer the study lasted. The cyclists’ memory kept improving, while the noncyclists stayed in one spot, both in terms of fitness and memory.

  When the cyclists’ brains were studied with MRI, the scans revealed that improved memory went hand in hand with increased blood flow to the hippocampus, our memory center. This increased blood flow would certainly explain why the hippocampus works better. Interestingly, it looks like the blood flow increases first, after which memory improves.

  An instant memory boost

  Are you as impatient as I am and feel that six weeks is way too long to see progress? The truth is training improves memory immediately! It has been observed that those who did best on the test were those who trained right before the test. Moderately fit people who train right before a memory test typically do better than fit people who haven’t trained beforehand, illustrating that training has an immediate effect on memory.

  If you want to boost your memory, train while you learn something.

  But if you’d like to boost your memory to the max, you will need to move and learn at the same time—studying while walking on a treadmill, for instance. This is good to keep in mind even if it may not always be possible to do, of course.

  We don’t know why individuals who learn something while they exercise remember things better. What probably happens is that the blood flow in the brain increases when you move, the same way blood circulation increases in muscles. This blood flow boost is instantaneous, and when the brain gets more blood, memory works better.

  Don’t work out to the point of failure

  Boosting your memory through exercise doesn’t mean it’s just a marginal effect that can be measured only in scientific experiments; on the contrary, you will notice these effects. In word tests that measure word recall, it has been shown that you can learn up to 20 percent more words if you’re physically active before or while you learn the words, compared to when you are at rest. Those of you who are studying for an exam or who need to learn material for work should think twice before deciding you don’t have time for a walk. That walk is probably time well spent.

  From a memory standpoint, walking or light jogging is enough to achieve the best effect. However, if you work out to the point of failure and end up exhausted, you run the risk of remembering less. Muscles require so much blood that blood flow to the brain decreases slightly, which may be why your memory doesn’t work as well. Besides, if you train hard, the brain seems to focus on your movement and not on what you’re trying to learn. For example, if you run fast while listening to something
you need to remember, your brain is going to focus on running, not on what you hear.

  Can running make me a better piano player?

  Our memory is not all about learning words, reading texts, or remembering what we did last week. We also have a motor memory for movements, like when we learn to hit a forehand in tennis or play a piano piece. The basis for all learning is that new connections are created among brain cells, which makes you wonder if the conditions for learning a motor skill improve if you exercise. Naturally, your forehand gets better if you practice only that movement. Does this mean that your ability to master the forehand will improve if you run first? Or that biking can improve your ability to learn to play the piano?

  To gauge how physical activity influences our motor memory, subjects were asked to play a simple computer game using a joystick to follow a point moving across a screen. The game, which seems simplistic, activates many areas of the brain and is occasionally used in research to measure motor ability.

  For this test, subjects were first required to run or bike and then proceed to the computer game. Then they were asked play the game again after some time had passed to see if they improved. Just as your forehand improves with practice, you naturally improve at playing a computer game after some practice. But here’s what was noteworthy: when tested, those who had been physically active prior to playing the game were better at it. To be clear: the only difference was that some of the test subjects exercised before the game, and there were no variations in the time spent practicing the game. Nonetheless, those who exercised did better. Some aspect of movement in and of itself helped them to learn to play the game better without having to spend more time practicing.

  How then can physical activity make us perform better at motor activities? We can only speculate, but in the minutes to twenty-four hours following the acquisition of a new skill, memory consolidation happens. This means that the memory, whether of learning a piano piece or a computer game, is transferred from short-term memory to long-term memory. Let’s say you play a simple tune on the piano a few times. You rest for one minute, and then play the tune again. You’ll probably remember it quite well as it sits in your short-term memory. But how well will you remember that tune tomorrow? That depends on how strongly the memory has been imprinted, or consolidated, as a long-term memory.

  The hippocampus is important in how memories get transferred from short-term to long-term status. As we’ve seen, exercise makes the hippocampus cells pump out BDNF, which reinforces the connection among brain cells. If we engage in physical activity before learning, BDNF will be pumped out while the memory changes from short term to long term. The conditions for that memory to go into long-term storage will probably improve, since the transmission from short-term to long-term status happens not within minutes of learning something, but more like twenty-four hours afterward. This corresponds quite closely to what the computer game test revealed, which is that exercise starts having an effect one day after learning.

  This means you will probably become a better piano player if you’re physically active before you practice your piano scales! And it signifies that you’ll increase your chances of learning that golf swing if you go for a run or a bike ride before heading out on the golf course. Through exercise, you can strengthen your brain’s memory during that crucial phase when the memory of the piano piece or golf swing—or whatever skill you wish to learn—is being saved to long-term memory. The brain cells’ ability to create strong and lasting connections between one another increases, and it seems to apply to situations where you are acquiring a language or a motor skill.

  MENTAL PATHS

  Basically, our memories are a cluster of brain cells connected to one another. When we experience something new (i.e., create a new memory), new connections called synapses are created. These connections don’t mean that the cells physically touch one another, but that an end terminal sends a chemical message between them. Nobel Prize winner Santiago Ramón y Cajal described it poetically as “brain cells holding hands,” even though cells don’t actually touch.

  How hard cells hold on to one another depends on how many times they make contact. If you learn a new phone number, a new contact will be created. Each time you dial that number the contact will strengthen—the cells hold on tighter to one another—and you’ll remember the number much better each time you dial it. Perhaps you remember that “Neurons that fire together wire together!” On the other hand, if you only learn the phone number once, you will forget it. The connection will weaken if it isn’t reinforced, and the brain cells lose the connection.

  Similarly, we can look at memories as mental paths that are created among the brain’s cells. Well-trodden paths stay put, and so that memory remains. Paths that were recently walked on a few times will grow over and disappear. Some things create a well-worn path right away that embeds itself as a memory for life.

  A unique or an unusually intense experience can leave a lifelong mental imprint, even if the path was only “walked on” once. This applies especially to emotionally charged events that have negative connotations, such as threats or danger. Those types of memories are very important from a survival standpoint, and consequently they have priority in the memory bank. Evolutionarily speaking, it’s critical to remember what is dangerous so you can avoid it in the future. This means that if you witness something horrible or experience a life-threatening situation, you will most likely remember the event in detail for the rest of your life. Other things that are not as unique or charged, like tying your shoe laces, won’t leave a path. The cells hold on to one another for a short while, and then they let go. You’ll quickly forget what you did.

  Bearing this in mind, you can see how physical activity may contribute to mental paths being well-worn and to cells “holding hard on to one another.” As you’ll recall from the beginning of this chapter, exercise causes brain cells in the hippocampus to pump out more of the substance called BDNF. BDNF will strengthen the connection among brain cells so they “hold hands even harder,” which, to continue with that analogy, means that the mental path becomes well-worn faster. The memory becomes stronger, and, consequently, we remember what we’re doing. We remember better, and we learn better.

  Physical activity increases levels of BDNF, which in turn reinforces the connections among the brain’s cells, making it probably one of the most important reasons why exercise is so beneficial for memory.

  Does too much training impair memory?

  From the brain’s perspective, it’s debatable whether more exercise is always better—if you can have too much of a good thing. Is a grueling race such as the Ironman Triathlon, during which participants remain active for ten to twelve continuous hours, good for memory and the brain? We don’t know for sure yet, but there is a lot to suggest that such a big effort is more damaging than beneficial to the brain and for memory—at least in the short term.

  By selecting from a large pool of mice, American scientists were able to breed specimens that were obsessed with running: those that ran the most could mate, and the offspring that moved the most were in turn allowed to mate. The scientists continued in this manner until they had produced mice that would, of their own free will, run almost three times as much as regular mice. In fact, these ultra-runner mice ran the equivalent of many miles a day for a human being.

  The mice’s memory was then tested by letting them try out a new maze. Normally, mice that run are quicker to find their way around a new space, since exercise improves memory. However, the ultra-runner mice took much longer than normal to learn the new maze. Their memory was worse, and their blood had high levels of the stress hormone cortisol, which is central to the body’s stress response. Cortisol levels typically drop after we’ve been physically active, so the mice that ran regularly should have had less stress. Instead, these ultra-runner mice seemed to be chronically stressed out.

  We don’t know for certain yet if this carries over to humans, but it looks like there is a degree at whic
h exercise becomes too much to handle for the brain. At this point, the stress response no longer decreases but increases, and memory becomes poorer. Currently we don’t know exactly where that stress cut-off is—it probably varies from person to person. However, one conclusion that could possibly be drawn is that anyone who participates in ultra-marathons or similar events should not do so with the intention of strengthening their brain and improving their memory, since they may in fact suffer the opposite outcome. A long walk or a thirty-minute run is plenty for the brain—it’s probably much better than running for several hours.

  A walk or a thirty-minute run is enough exercise for boosting memory; it’s probably better than running for several hours.

  YOUR BRAIN CAN CREATE NEW CELLS

  At the dawn of the 1900s, most scientists agreed that the adult brain could not generate any new cells. If we cut ourselves, the cut heals over and new skin cells are produced. Likewise, new hair cells and blood cells form continually. Most of the body’s organs are capable of regenerating cells, but nobody thought this to be true about the brain, the explanation being that the brain, comprised of its one hundred billion cells, is so incredibly complex that newly generated cells in an adult brain could not fit in together with the cells originating from birth. It seemed as improbable as thinking you could dismantle a computer, randomly plug in a few circuit boards, and hope the computer would run better. This belief is why many of us were taught in school that the brain we have at twenty years of age is the one we must make do with for the rest of our lives. I remember it being said that if you take a swig of alcohol, you’ll lose fifty thousand brain cells that you’ll never see again.