Think Smart: A Neuroscientist's Prescription for Improving Your Brain's Performance

INTRODUCTION

What should I do to keep my brain working at its best?

I’m frequently asked that question. It makes sense as I’ve written eighteen books about the human brain. But I recently decided to undertake a personal odyssey aimed at discovering what I can do to improve my brain. This seemed especially important, since I will soon be at an age when brain function typically declines unless deliberate steps are taken to maintain it.

I come to this task from a unique vantage point, based on my experience as both a neurologist and an author. Over the years, I’ve become acquainted with many of the world’s foremost neuroscientists (brain researchers). I’ve talked with them during neuroscience meetings, observed them in their laboratories, and read their published writings in which they explain their discoveries. What could be more natural, I wondered, than to ask these brain scientists, the best in their field, "What are you doing to keep your brain functioning at its best?"

Their answers often surprised me. And I suspect they will surprise you.

Using their answers, coupled with my own work in cutting-edge brain research, I’ve set out in these pages my personal program to improve your brain’s functioning. It can be used by anyone interested in developing and maintaining an optimally functioning brain. Whether you are young or old, rich or poor, male or female, these insights will help your brain to be more efficient, more effective, and more engaged.

PART ONE

Discovering the Brain

When I was a medical student, neither teachers nor students placed much emphasis on the brain. The curriculum included only a first-year course in neuroanatomy, followed two years later by a one-month rotation spent working with patients on the neurology wards. After graduation, most medical students tended to avoid specialty training in careers devoted to treating the brain (neurology and neurosurgery), based on the general perception that not much could be done to heal or even improve the lives of many of the patients afflicted by brain diseases. I remember vividly my father’s disappointment when I told him I was interested in neurology and psychiatry rather than obstetrics (his specialty). You can’t do anything for most of the patients you’ll encounter in either of those specialties, and it’s awfully depressing to just diagnose and not treat, he told me.

A lot has changed since then. We have learned more about the brain in the past decade than we did in the previous two hundred years. If he were still alive, my father would be amazed at the effective treatments now available for many brain diseases such as multiple sclerosis, migraine, and epilepsy, to mention just the most common. Neuroscience (brain science) is currently one of the most popular career choices among students attracted to science. Psychiatry and neurology are in the process of merging into the hybrid discipline of neuropsychiatry. But these advances didn’t happen spontaneously. The advance from nihilism and pessimism toward curiosity and hope was stimulated principally by new ways of imaging the brain.

Until the middle part of the twentieth century, what little was known about the brain consisted of a mélange of speculation and dogmatism based on hosts of hoary old men staring through microscopes at brightly colored dye-stained neurons. Thanks to advances in brain-imaging techniques over the last thirty-plus years, it’s currently possible for neuroscientists (many of whom are now women) to observe the development of the brain in real time and without any need for either speculation or dogmatism. The principle behind these illuminating (in both senses of the term) imaging techniques is straightforward: blood flow to the brain varies with activity. The greater the activity, the greater the flow of blood needed to replenish the oxygen and glucose used by the active neurons. This isn’t any different from what happens elsewhere in the body.

When you lift a hundred-pound barbell at the health club in an effort to attract the attention of someone nearby in whom you’re romantically interested, blood flow increases in the muscles of your arms and chest based on the increased need by those muscles for oxygen and glucose. Similarly, when you use a specific circuit in the brain, the components of that circuit will become more active and call on the circulatory system to provide additional glucose and oxygen. Positron-emission tomography (PET) and functional magnetic resonance imaging (fMRI) detect the changes in blood flow within active parts of the brain and record them while the subject lies within a special scanner.

Thanks to fMRI imaging and other techniques, we know that the brain never wears out; it gets better the more we use it; it changes in structure and function throughout our lives. As a consequence of this plasticity we sculpt our brains according to our life experiences. As a result, no two brains are exactly alike, not even the brains of identical twins who, while they share the same genetic makeup, don’t share identical experiences. Due to this diversity in the brain’s organization and structure from one person to another, it’s often possible to reach valid conclusions about a person on the basis of his brain’s organization.

For instance, while looking at an fMRI, a trained observer can distinguish the brain of a skilled pianist from that of a nonpianist. That trained observer will note that the pianist’s brain shows increased activation in the finger areas of the motor cortex while she listens to a piano concerto. The same thing happens if she just watches someone playing any musical composition on the piano. But it won’t happen if she observes that person merely making random finger movements on the keyboard: under these circumstances, the pianist’s brain responses won’t differ from those of a person with no special musical expertise or interest. A similar specialization occurs in dancers. A ballet dancer will show greater brain activation while he watches other ballet dancers perform. This won’t happen if he watches ballroom dancers.

Nor is brain specialization limited to the arts. If that pianist at the conclusion of her performance takes a cab from the concert hall to her apartment, her cabdriver’s brain is likely to have an enlarged hippocampus—a brain area heavily involved in spatial visualization and navigation. The same is true for any specialized occupation: A surgeon will show greater activation in the hand area of the motor and sensory cortex than will a doctor who doesn’t perform surgery.

The pianist, the ballet dancer, the taxi driver, and the surgeon have shaped their brains by virtue of their experiences. The same thing is true for all of us. We create new patterns of neuronal organization according to what we see, what we do, what we imagine, and most of all, what we learn. Learning something new involves establishing a pathway within the brain made up of millions of brain cells. As we learn more, these pathways increase in complexity—a process similar to the branching of a tree as it grows.

Thanks to its plasticity, the brain can be thought of as a tree of knowledge. When in full bloom, a tree blossoms: roots give off branches, twigs, and leaves. Similarly, learning increases interaction within the brain with more and more other neurons establishing fuller and richer circuits. But if learning stops, the brain, like a tree losing the luxuriant structure seen at full bloom, reverts to a state corresponding to that of a tree in winter.

You can picture human brain development as a continuum ranging from infant-child to adolescent to adult and, finally, to the mature older brain. Each stage of development along this continuum calls for specific approaches to brain enhancement. Equally important, lessons learned at one stage of brain development can be usefully applied at every other level, starting from its earliest inception until its eventual dissolution and demise in old age. Thus knowing principles drawn from the study of the infant brain will help you enhance your adult brain.

Indeed, infant and adult brains share many of the same challenges: stimulation but not overstimulation, maximizing plasticity, establishing and maintaining nerve cell (neuronal) circuits in the face of a steadily decreasing loss of neurons, among others. That last point (fewer cells but greater connections) may strike you as strange, even paradoxical, as it did me when I first learned about it during my neuroscience training. Indeed, this improved function with fewer components principle is one of the great paradoxes of the human brain.

At birth our brain possesses almost all of the neurons it will ever have. Maximum brain cell number is achieved during an explosive growth period that takes place between the third and sixth months of life. During the next three months, before birth and extending into the first two years of life outside the womb, the total number of neurons decreases, while the functional connections among the surviving neurons, the synapses, increase. Thus the newborn infant is equipped with considerably fewer neurons than it possessed in the womb but a far greater number than it will have as an adult.

Now here’s the paradox: As we progress from infancy to childhood to adolescence to adulthood, the brain’s performance improves and yet does so with fewer neurons. No mechanical device operates with greater efficiency as its components are gradually taken away. Imagine removing parts of your car’s engine every year and thereby improving its performance. A similar situation exists in regard to every part of the human body except the brain: remove healthy heart, lung, liver tissue, and you wind up with a compromised organ.

Enriching the Brain

Only recently have neuroscientists been able to account for this odd state of affairs whereby we have more brain cells during the period when we’re learning to say Mama and Dada than when we’re learning geometry or later heading up a Fortune 500 company.

In order for the brain to develop normally, large numbers of brain cells must first be generated (a period referred to as proliferation) and many of them later eliminated (a process neuroscientists refer to as pruning). Pruning results in fewer but faster and more effective brain cell connections (synapses). An estimated 40 percent of synapses generated during infancy are eliminated by adulthood. Use it or lose it is the operative term that describes this process—and it applies across the entire life span of the brain.

Whether we’re in the bassinet or in the boardroom, those brain cells that establish connections with other cells will be maintained; those that fail to link with others will die off. A similar principle—dubbed neural Darwinism by the Nobel Prize-winning neuroscientist Gerald Edelman—applies at the level of brain cell circuits (networks). Those brain circuits that are actively maintained and challenged will endure and grow stronger; those that are used infrequently, if at all, will gradually disappear—sort of like friendships.

As part of this process of challenge and maintenance, novelty and enriched experiences work like fertilizer on brain growth and development. We know this from a series of now famous experiments comparing the brains of two groups of caged rats, which were carried out in the 1970s by neuroscientist Bill Greenough, then at the University of Illinois at Champaign-Urbana.

One group of rats lived alone in the equivalent of lock-down (no companions, nothing to do, etc.). The second group was treated more like white-collar criminals given the opportunity to spend their time in comparatively plush surroundings (at least by lab rat standards). Their cages were fancier and furnished with wheels to spin, ladders to scale, and other rats to play with—the rat equivalent of Disneyland, as Greenough characterized it. These more favorably endowed rats became more physically and socially active—networking and coexisting with other rats in the kinds of competitive though generally peaceful projects possible for a rat spending its days and nights in an animal lab in Illinois.

When studied under the microscope, the brains of the rats raised in the enriched environments contained 25 percent more synapses per neuron than those of the isolated rats. This increase in synapses translated into cleverer rats that were quicker to wend their way through mazes and learn landmarks faster. The message from the Greenough experiments seemed fairly straightforward: If you want a rat to grow up smart instead of stupid, make its life more challenging; increase the rat’s opportunities for sensory stimulation, physical exercise, and socialization. Each of these factors increases blood supply to the brain, enhances brain development, and leads to the creation of smarter rats.

When I first learned about Greenough’s research, I was impressed but skeptical. Shouldn’t his findings be placed within the context of the normal life of a rat? Even the rats in the enriched-environment cages lived incredibly impoverished lives compared with their wild cousins that live in sewers and back alleys richly supplied with complicated mazes, tunnels, and debris—to say nothing about the huge numbers of other rats that must be dealt with. From that vantage point, it’s fair to say that all of the rats in Greenough’s experiments lived environmentally impoverished lives. Here’s what I think is a reasonable summary of his enrichment research: The rat living in an enriched laboratory environment winds up with a greater number of synapses and more enhanced brain development than a rat living in anything other than its natural environment outside a laboratory.

Having established the value of novelty and an enriched environment as stimulants for brain development in rats, Greenough’s research prompted a tantalizing question: Would environmental enrichment lead to enhancement in the human brain? Obviously, a similar experiment could not be carried out in humans. But even though the supporting evidence is less direct, it’s nonetheless persuasive. Not only do infants raised in institutions show stunted intellectual and social development compared with other infants transferred from the institution to an adoptive family, but their brains also have fewer connections linking different parts of the cortex. And children placed in high quality day care (lots of toys, interaction with other kids, and dedicated resourceful teachers) go on to perform better in elementary school than children from centers where the emphasis is on supervision and control. Nor does the influence of social and cultural enrichment on brain performance end in childhood; it continues throughout the life span. Education, both formal and informal, and practical experience are the greatest environmental enrichment agents. Thanks to new imaging techniques, it’s possible to see the brain changes induced by learning and experience. For example, among London cab-drivers, those with the most experience in successfully navigating that city’s labyrinth of streets show the most significant enlargement of the hippocampus—a sea horse-shaped structure known to be important in spatial learning and memory. Other imaging studies demonstrate that, in general, life experiences leading to the development of special abilities (musical, athletic, artistic) also induce structural changes in the brain areas that mediate these abilities.

Maturing the Brain

When does the brain reach maturity? That depends on your definition of maturity. From the behavioral point of view we can all bring to mind people who never seem to mature. Throughout their lives they continue to grapple with issues involving authority, identity, and self-assertion (among others)—issues that the majority of people resolve before casting their first vote. But if we talk about maturity from the point of brain structure and function, the story is quite different.

Before the 1970s it was widely believed that all of the different regions of the brain developed at same time. But in the 1980s this belief was found not to be true. Brain regions that control primary functions such as movement, seeing, and hearing develop first, followed by areas concerned with language and thinking. The last brain regions to mature are the prefrontal and temporal areas, which integrate attention, language, and decision making. This sequence of development is mirrored behaviorally: burps precede elocution: the infant sees and hears prior to speaking or learning words and concepts.

This insight into the sequential development of the various parts of the brain resulted from revolutionary imaging devices such as magnetic resonance imaging (MRI), which provides a window on brain structure—the geography of the brain—coupled with functional MRI, or fMRI, which shows color-coded pictures of ongoing brain activity. Both imaging devices reveal striking differences between the child and adolescent brain and its adult counterpart.

Total brain volume reaches a peak at about eleven years in girls and fifteen years in boys, and is followed by a slow decline over the adult years. The most striking developmental change occurs in exponential growth within the frontal lobes.

Located farthest to the front of the brain, the frontal lobes are responsible for our most evolved feelings and behaviors such as ethics, altruism, and compassion. The frontal lobes are also important in foresight, planning, and follow-through. Foreseeing the likely consequences of one’s actions requires normally functioning frontal lobes. Some adults seem to be frontally challenged when it comes to these frontal-lobe functions.

Since the frontal lobes develop at a much slower pace than other brain areas, the humanizing qualities mediated by the frontal lobes are in scant supply early in life. Spend a few minutes in a playground and you can observe that toddlers and very young children need to be reminded to share, to avoid hurting other children’s feelings, and to settle disputes without recourse to verbal or physical attacks. A similar need for externally imposed structure in the absence of internal controls occurs among some adults. Although I’ve never committed a crime, my work as a forensic neuropsychiatrist has taken me behind the walls of more prisons than I care to count. I’ve found that many prisoners, especially those serving time for violent crimes, suffer from deficiencies in frontal lobe function. They can’t plan their lives or control either their emotions or their behavior. In some cases, I can demonstrate these frontal lobe deficiencies through testing and imaging. This can prove helpful by providing a partial explanation for the actions that led to the prisoner’s incarceration. In other instances, the studies are normal by the criteria of currently available technology.

For those of us fortunate enough to possess brains with frontal lobes that underwent normal maturation, the process began in adolescence. As the frontal lobes begin to mature, each neuron becomes a component in any number of vast interconnected networks. Just as a person can simultaneously participate in many networks (work, church, local community, clubs), so too the individual neuron may participate in multiple circuits and networks within the brain. This social analogy is a good one for understanding the brain throughout its life cycle. Just as the totally isolated human being operates at great disadvantage, a