Boost Your Brain (5 page)

The (Much-Maligned) Middle-Age Brain

Even given that most people don’t use their brains to their full potential, the middle-age brain probably gets a bit of an unnecessarily bad rap.

People in their fifties and sixties often report feeling mentally slower than they used to. Such slowing is typical and can be the result of a variety of factors, from normal aging, to medications they’re taking, to lifestyle choices they’re making. But while their brains probably aren’t functioning as well as those of people twenty years younger, most people don’t experience a
rapid
decline in processing speed, working memory, or learning in midlife. Absolute processing isn’t typically a victim of normal aging either. A fifty-year-old can memorize a list of words just as well as a twenty-year-old, although perhaps not as quickly.

And as it slows down in some functions, the mature brain still has one advantage over the youthful noggin: experience. With every experience we have, we gain information that will factor into future decisions. As a result, by late middle age we tend to be more reasoned, less emotional, and better decision makers. If you don’t believe that, you can ask my brothers. Twelve and fifteen years younger than me, more fit and with brains that are no doubt a little quicker than mine, they still lose to me in tennis pretty much every time we play. Why? Their hard hits and quicker reflexes are no match for my years of practice. Much to their chagrin, they have to admit that I know exactly how to place the ball just out of their reach. Experience trumps mental—and physical—speed.

CHAPTER TWO

How to Grow a Brain

B
Y THE TIME
I cradled Mrs. Grey’s brain in my hands, I had already benefited from several years of medical education at Harvard and Johns Hopkins. I knew that a brain like Mrs. Grey’s carried with it undeniable liabilities. Examining her mottled and shrunken cortex, I could see why Mrs. Grey’s mental capacity had declined in her final years. With the destruction of neurons and synapses, the deterioration of fiber bundles, and the collapse of blood vessels, no doubt she would have struggled to think—to remember the names of loved ones, to navigate from her home to the grocery store, and to recall what she needed once she got there.

And yet, there were so many unanswered questions. Would Mrs. Grey’s brain look different if she’d lived differently? How much different? What exactly would she have had to do?

Countless scientists have worked over the years to produce the research proving that brain shrinkage is tied to memory loss and other cognitive problems, and that certain actions—like the treatment of vascular diseases—may help slow such decline. It’s an area I found so fascinating that, in 2009, several colleagues and I conducted an exhaustive review of the literature and documented the hows and whys in a paper published in the medical journal
Nature Reviews Neurology
.
¹
That paper provided a concise explanation of all the factors that push us into cognitive decline late in life. In short, our research showed, late-life dementia results from a constellation of genetic and environmental factors—from certain Alzheimer’s-related genes to obesity, diabetes, hypertension, head trauma, systemic illnesses, and obstructive sleep apnea—all of which work to shrink the brain.

It was a rather tidy summation of just what causes brain shrinkage. And it offered something of a recipe for helping the average person reduce his or her chances of meeting such a fate. The next question, of course, was “could we go beyond that?” It’s one thing to slow the pace of brain aging but could we take it one step further and
grow
the brain—even a healthy brain? To find out, I dove into the research of the day, reviewing some two thousand medical journal articles. My focus was primarily on the hippocampus, since it is the brain’s most malleable region.

You probably already know what I found, even without having read the resulting journal article, published in 2012 in
Nature Reviews Neurology
.
²
We can, of course, not only reverse the brain atrophy associated with aging but also expand the brain’s size—even before shrinkage begins.

When an author submits an article for publication in a medical journal it is first sent to peers in the author’s field. They provide the critical eyes that ensure published articles are scientifically sound. Often reviewers tear into such papers with critical zeal. It’s part of the process. In this case, however, the reviewers were uniform in their praise: not one of the three neurology experts who reviewed the paper offered any major criticism.

I’ll get you started in chapter 3 on your own plan to grow your brain, but first you need to know just how it’s done. In short, brain growth occurs through four key avenues.
³

The Core Four

Adding Synapses

We’ve long known that when you learn something new you create new synapses—a process called synaptogenesis—and that when you continue to use those synapses you strengthen them. But it’s only in recent years that we’ve come to understand how significant the impact of such “brain training” can be and how quickly it can happen.

In fact, as you’ll read in
chapter 7
, repeated stimulation of synapses can lead to measurable structural changes in the brain in as little as several weeks. Examine the brain of a person learning to juggle or play golf and you’ll find the portions of the brain implicated for coordinated hand and eye movements—the cerebellum, parietal cortex, and frontal lobes—are stronger, and bigger, than in someone who never juggled or played golf. This is, in part, due to synaptogenesis. The same principle applies to ballet dancers, basketball players, mathematicians, violinists, cab drivers, or anyone else practicing or learning a new skill.
⁴

Bolstering Highways

As you know, the brain’s neighborhoods communicate with each other through a network of fiber bundles, which carry signals back and forth. When your hippocampus needs to communicate with your frontal lobes, for example, it sends a message via these pathways. How well they function depends on two things: how many synapses there are between the neurons that make up these fiber bundles and how well myelinated those neurons are. Adding synapses helps strengthen the connections, while preserving and nourishing a strong myelin coat on the axons through myelination helps to ensure messages zip speedily along.

Adding (and Aiding) Blood Vessels

The brain is a richly vascularized organ, fed by an intricate system of blood vessels that carry nutrients and oxygen to every cell. In fact, a third of the brain is made up of blood vessels and a full 20 percent of the heart’s output goes to the brain, despite the fact that the brain only accounts for about 2 percent of a person’s body weight.

The health and vibrancy of this network of blood vessels is crucial to the brain’s ability to thrive and grow. If the network is clogged or shrunken—by blockages that slow or cut off the flow of blood—neurons can’t thrive. Some die; some merely fail to grow. But growing the brain isn’t just a matter of keeping existing blood vessels in good health. It also relies on actually increasing that network, by developing new blood vessel branches through angiogenesis. As you’ll soon read, exercise has actually been shown to promote angiogenesis, which in turn brings more blood and oxygen to the one hundred billion cells in the brain.

Neurogenesis

We’ve long known that neurogenesis occurs in the developing brain. But only in recent years has the field of neuroscience offered up conclusive evidence that the human brain is capable of growing new cells even in adulthood, a concept that wasn’t even taught to doctors in training during my medical school days in the 1990s.

That’s not to say the foundations of such discovery were unknown. In fact, as early as the 1960s there was evidence that the adult brain is not fixed in size, that neurogenesis goes on well past childhood. It was a seemingly outrageous notion at the time and the scientific community largely dismissed it. That is until the late 1980s, when researchers conducting animal studies began to document the phenomenon in earnest. Before long they had proven that neurogenesis was not only happening, it was also closely tied to learning. A 1989 study of songbirds, for example, found that adult canaries grew new brain cells each year as they learned new songs in order to mate. Even so, as late as the early 1990s there was still a lot of skepticism in the field of neuroscience.

Enter Dr. Fred Gage, a professor in the Laboratory of Genetics at the Salk Institute for Biological Studies who has studied neurogenesis extensively. For Gage and others, the 1990s would prove an opportune time to dispel the doubt, thanks to emerging tools that allowed them to stain, mark, and even count neurons in a way they never had before.

And dispel the doubt they did, offering up proof in 1997 that mice living in enriched environments—with social interaction, toys, and running wheels—had dramatically more hippocampal neurons than mice who lived in bare cages.
⁵
In fact, Gage’s study showed that new neurons had grown in the brains of both groups of mice, but in the enriched group social interaction, toys, and running wheels seemed to help those fledgling neurons survive and mature. In that group, 90 percent of those new neurons thrived, compared to a normal survival rate of just 50 percent.

The results were fascinating, but the real clincher came when Gage and his team noted neurogenesis for the first time in humans.
⁶
That study labeled and counted new neurons born in the adult brains of patients with terminal cancers, who had agreed to donate their brains after they died. The human brain, Gage’s study proved, wasn’t fixed in adulthood after all. The news was a breakthrough in the way we think about the brain, crushing the myth that the brain only deteriorates with aging.

Since then, Gage and researchers around the world have helped to fill in the blanks about neurogenesis in the adult human brain. We now know that new neurons are born in the brain every day, but unless certain conditions exist (one of those conditions is the presence of the brain fertilizer BDNF, which you’ll read about in a moment), they’ll simply dissolve, never to grow into adult neurons. We know that neurogenesis happens throughout life but occurs to a lesser degree as we reach old age, giving us ever more reason to build up brain reserve in midlife. We know that other factors, such as sleep, may alter neurogenesis in the brain.

We also know that growth in the various areas of the cortex and hippocampus translates to better brain performance, as you’ll read in part II of this book, and—perhaps most exciting of all—with simple behavior modifications it’s possible to see remarkable change in the size of these brain areas in mere months.

In fact, as recently as 2012 evidence has emerged that some changes in the brain occur more rapidly than we knew—becoming evident after as little as two hours—and to such a large degree that they can be seen on MRI.
⁷

The Core Four

Brain growth can happen through lifestyle changes that are known to build synapses, bolster the brain’s highways, nourish and grow its blood vessels, and promote the development of new neurons.

Fueling Growth

You’ve heard it a million times: eat brain food, exercise, sleep well, and you’ll be rewarded with a “fit” brain. But what does that really mean? And what else can you do to enhance your brain’s performance? As you’ll discover, there is a wave of developing science behind a variety of techniques and practices that will put you on a path to grow your brain and boost its performance, both now and in the future.

In the past, efforts to boost brain performance have focused on slowing brain aging by preventing inflammation or limiting the risk of brain-damaging events such as a stroke. Those factors still matter when it comes to brain growth (your brain won’t grow if it’s shrinking due to harmful effects), but it’s become increasingly clear that growing your brain really boils down to capitalizing on three mechanisms that are crucial to brain growth: oxygen, BDNF, and healthy brain wave activity. These mechanisms fuel the core four—adding synapses, supporting and growing a network of blood vessels, bolstering the brain’s highways, and promoting neurogenesis. You’ll read about them throughout this book, but here is the short story:

Oxygen

Unlike the cells in the rest of your body, neurons are constantly abuzz with activity, firing thousands of times a second, even when you’re sleeping—a level of demand that requires tremendous oxygen flow. Oxygen keeps these neurons firing and is a critical ingredient in synaptogenesis and neurogenesis.