Secret Life of the Grown-Up Brain (17 page)

Most of the recent research has looked at the relationship of cognitive reserve to dementia because, as a slowly progressing disease, dementia is easier to measure. Still more controversial has been the idea, as mentioned by Scarmeas and many others, that this mental cushioning could also soften the less forceful assaults of normal aging.

But in just the last few years there has been a shift. Many now believe this extra brain reserve is real. And it appears that the way we live our lives can have a very real impact on the overall power, strength, and staying power of our brains.

“Cognitive reserve is a very powerful idea,” says Stern. “But it is also a simple one. The fact is that there is not a linear relationship between pathology in the brain and clinical manifestation of that. Something is mediating and some do better than others. And this is not specific to even aging or Alzheimer’s. Those are good places to see it. The evidence is out there.”

As the research into cognitive reserve has exploded, its effects can be seen in wider and wider areas. In particular, researchers now want to know what it means to people who are hitting middle age and beyond. Do we have to start building this backup brainpower as babies? In the womb? Or can we still grab a little if we tackle it when we are past fifty? How about sixty?

The most recent studies suggest that brain reserve can be built anytime in our lives. One long-term study found that those with high socioeconomic status and fully engaged in their environment had the least intellectual decline during a fourteen-year period (widowed women who had never been in the workforce and who had a disengaged or lonely lifestyle did the worst). Another study included in the Scarmeas and Stern review—of World War II veterans tested twice over forty years—found that participating in intellectual activities was related to intellectual performance later in life. Similarly, a well-known British study—a long-term look at people in England, Scotland, and Wales born right after World War II—found that social class, occupation, and education at age twenty-six helped shape cognitive ability at age fifty-three.

More recently, in 2007, a study of workers at a lead-smelting plant found that among adult men with the same blood-lead levels, a result of exposure to heavy metals known to cause neural damage, those with the highest reading scores, while not protected from declines in hand-eye coordination, were somehow shielded in cognitive areas. The men in the group of better readers performed 2.5 times as well on tests of memory, attention, and concentration tasks not necessarily related to reading. The study’s author, Margit L. Bleecker, a neurologist at the Center for Occupational and Environmental Neurology in Baltimore, said she now is convinced that “the brain is like a muscle” and can be pumped up at any age. “Those who are cognitively more active, exercise more, and are more socially connected have more cognitive reserve,” Bleecker says.

Certainly early development of the brain is key and head injuries along the way don’t help, but research increasingly finds that reserve can be added at middle age and beyond. In a Scottish mental-health survey, children born in 1921 first had their IQ tested at age eleven and then at age eighty. While IQ at age eleven was a decent predictor of how well a person would do later on—and IQ is partially inherited—there was clear evidence that we’re not necessarily stuck with what we are born with. Some in that group were able to push their scores up significantly. Something was changing their brains for the better—even well past childhood.

Granted, there are still disagreements and doubts out there. Even Nick Fox in London, who reported on the case of the Chess Player, believes that cognitive reserve has become such a hot topic that all sorts of grand and largely unsubstantiated claims are now being made in its name. Even with the Chess Player, he says, the question remains: Did he withstand the assault of Alzheimer’s for so long because of “something he did” in his life—that is, read, play chess, or become highly educated—or because that’s just how his “high functioning brain was”?

But most evidence now suggests that we can make a difference by what we do; we can boost our reserve, even when older.

“You are not just born with cognitive reserve, and that is the most encouraging piece of this,” Stern said. “It seems to be malleable even in later life. The thing is, we are not sure what is the most protective thing you can do—is it gardening or particle physics? We need to figure that out.”

Perhaps more than anyone else, Stern remains on the trail of cognitive reserve. Step by complicated step, he is trying to find out what it is in our brains that can help—and what we can do to help our brains. Some of Stern’s most recent research, for instance, has confirmed that it is not just complex occupations that make a difference to dementia but occupations that are highly physical.

“I used to have this ivory tower view of cognitive reserve, that it was linked to intellectually stimulating things,” Stern says. “Now I am trying to exercise, to go on the treadmill more.”

Many cognitive reserve studies have looked at large populations, so-called epidemiological studies that seek out correlations or trends. But in the past few years, researchers have also taken a more focused look inside the brain. A study in 2001 by Lawrence Whalley at the University of Aberdeen in Scotland found that among those with the same outward behavioral symptoms of dementia, the most educated also had more decay in their brain’s white matter, that crucial outer coating of brain cells. Again, this was an indication that those with more education were somehow able to cope with more damage and still function.

In one unusual study, researchers found that among a group of people who were depressed and received electric shock therapy known to cause cognitive problems, those who had higher levels of education recovered much faster. And a recent study by Shelli Kesler at Stanford University School of Medicine found that the more educated and those with larger brain volume even had a smaller dip in IQ after traumatic brain injury.

“I’m quite passionate about cognitive reserve,” Kesler told me. “I am definitely a believer. It’s just like an athlete is better at sports and would be more protected from heart disease than someone who is obese.”

“Cognitive reserve,” Kesler said, “is basically a type of neuroplasticity—we know from repeated animal and human studies that experience can alter our brain function and structure. I think cognitive reserve results from a combination of heredity and life experience. If you have smart parents, you will have a higher reserve—just like the athlete model—some people are just born with greater physical prowess—I’m trying to identify particular genes that might endow people with greater cognitive reserve or increased neuroplasticity.

“But just like an athlete—genetics will only get you so far—training and practice are essential. If you engage actively in mental and physical activities, particularly those that have a graded challenge (get more difficult as you progress), you also can increase cognitive reserve. It’s best to continually increase the challenge or difficulty level to keep on benefiting . . . a variety of mental activities that are new and stimulating will be the most helpful. I think this is one reason why people with higher education levels tend to have higher cognitive reserve—they have had a variety of mental stimulation and tend to seek this out.”

And, she said: “The best news is that neuroplasticity exists across the life span—you’re never too old to improve your brain function.”

Back in New York and now a true believer, too, Yaakov Stern at Columbia University is even trying to create cognitive reserve in his lab.

Much of what matters in the brain as it ages, Stern believes, will depend not on its hardware—how big, how many brain cells, how many branches and connections—but on its software, that is, how a brain operates. He believes that brains may age better if they also have the capacity to compensate, or “switch to plan B,” by using additional or alternate parts to do what they need to do.

This is a version of the two-brain idea. And it means that those who can, or who can learn how to, use more of their brains when they need to will be better off in the long run. These are the lucky escapees, who, Stern says, are “able to summon that compensatory response. They are used to engaging these networks and can do it more easily.”

Another key ingredient may also be basic brain efficiency. In one of his most recent studies, Stern found that, confronted with increasingly difficult problems, those with higher IQs used a smaller percentage of their overall brainpower to get answers. It was as if that group could “accelerate,” or ramp up, their brains with less effort.

Stern firmly believes that we can, by challenging our brains throughout life—perhaps by learning how to use our frontal lobes more efficiently—build up cognitive reserve. He is also trying to figure out if such brain efficiency can be taught to the middle-aged and older brain, when such training might be most beneficial.

“The best way I can explain this is to think of two swimmers,” he told me. “If you take a very good swimmer and ask him to swim a lap and then you have me swim a lap, at the end I will be winded and the good swimmer won’t break a sweat. He is more efficient. Then you ask us both to swim a mile and I won’t be able to do it at all but he will. He is not only more efficient but he has more capacity. Then you take that good swimmer and put a ten-pound weight around his waist; how does he do then?”

The ten-pound weight is middle age, old age, and disease. And the question on the table—one that is being pursued with a passion that would make that old seeker of the Fountain of Youth, Ponce de León, proud—is, how can we, even as we forget where we parked the car, build up reserve and keep our brains swimming?

Part Three: Healthier Brains

9 Keep Moving and Keep Your Wits

Exercise Builds Brains

Kevin Bukowski is forty-seven years old, and though he’d always been a runner, he’d slacked off lately. Then, offered free gym membership as part of a research study, Bukowski got serious about exercise. He woke up at five A.M. in his home in upstate New York, got onto a bus at six, and an hour later was on a treadmill in the gym across from Columbia University’s medical center in Manhattan, where he works helping to coordinate clinical trials. Every day, three or four times a week, Bukowski did the same routine: twenty minutes on the treadmill, twenty minutes of sit-ups. And what happened? At the end of five months, Bukowski was happy to find that he’d lost a few pounds, his body mass index went down, and he felt better “emotionally, physically, and spiritually. I just had more energy and I was not as tired at the end of a long day.”

But most important of all, his dentate gyrus went wild. His
dentate gyrus
? Hardly seems like something to get out of bed for, whatever it is. Dentate gyrus?

Well, yes. Over the past few years, the dentate gyrus, a small section of the hippocampus, an area crucial for memory, has emerged as a superstar in the story of the brain as it ages. And the dentate gyrus, it turns out, is particularly fond of exercise. Not long ago, in fact, the dentate gyrus caused a bit of a stir at a Columbia University lab. Early one afternoon, a group of scientists was watching a small computer monitor. The slide showed what had happened to the brain of a mouse that had spent weeks scampering on its little wheel, as many as twenty thousand rotations a day.

As the researchers watched the screen, tiny green dots appeared in the microscopic view of the mouse’s brain. The dots were new brain cells tagged with a dye that made them glow bright green. There were hardly any green dots in the brains of the mice that had not exercised, but in the mouse that faithfully and voluntarily ran on its wheel, there they were, as clear as day—small green dots in the middle of his dentate gyrus. Exercise had prompted the birth of new neurons—neurogenesis. And the scientists, seasoned veterans all, could hardly believe their eyes, in particular Scott Small, in whose lab the new baby neurons were born. “To see those green dots light up in the mice,” said Small when I spoke with him about that day. “To see it so clearly, new brain cells that came with exercise, it was impossible to ignore. My colleagues started putting on their sneakers.”

Over the past several years, neuroscience has been on a serious hunt to figure out how to nudge our brains in the right direction as they age. Are there real things that can help real brains in the real world? Education seems to buffer the brain. And there are a lot of other ideas—and loads of exaggerated claims—out there. Sudoku? Deep wave meditation?

At this point, the most promising answer is exercise. In one rigorous study after another, exercise has emerged as the closest thing we have to a magic wand for the brain, the best builder of branches, baby neurons, and, along with education, perhaps, the mental padding of cognitive reserve.

Scientists have suspected for decades that exercise, in particular aerobic exercise, is good for the brain, just as it’s good for the heart. Like all our cells, brain cells need oxygen, and the more our blood can spread oxygen around, the better. Blood flow is blood flow. What we’re told to do for our hearts—keep our cholesterol and blood pressure under control to make sure our arteries are as nimble as possible, for instance—turns out to be just as good, perhaps even better, for our brains. And Scott Small, with his green dots, is at the forefront of what is now an all-out effort to figure out how exactly this works.

Energetic and talkative, Small, at forty-six, is doing what he can to maintain his own middle-aged brain. He loves a fast game of tennis and recently took up snowboarding. The question is, as he reaches his sixties, seventies, and even eighties, will all that moving around leave his frontal lobes as finely tuned as his forehand?

In the spring of 2007, Small published an extraordinary study that suggests that the answer is yes. The study, starting with animals, first divided forty-six mice into two groups. For two weeks, one set of mice was kept in cages with running wheels and the other without, after which time the researchers scanned the mice to see what was happening to the blood flow in their brains. In fact, Scott Small’s lab was one of the first to develop the techniques to scan the brains of tiny mice, a step that not only lets researchers see what is happening brain cell by brain cell but can validate findings from sometimes difficult-to-interpret human brain-scanning studies. In this study, for instance, the mice were injected with a substance—now banned in humans—that clings to new cells and allows scientists to see precisely where new brain cells form. Then the researchers looked at microscopic slices of the mice brains.