Phantoms in the Brain: Probing the Mysteries of the Human Mind (3 page)

An amateur athlete lost his arm in a motorcycle accident but continues to feel a "phantom arm" with vivid sensations of movement. He can wave the missing arm in midair, "touch" things and even reach out and

"grab" a coffee cup. If I pull the cup away from him suddenly, he yelps in pain. "Ouch! I can feel it being wrenched from my fingers," he says, wincing.

8

A nurse developed a large blind spot in her field of vision, which is troubling enough. But to her dismay, she often sees cartoon characters cavorting within the blind spot itself. When she looks at me seated across from her, she sees Bugs Bunny in my lap, or Elmer Fudd, or the Road Runner. Or sometimes she sees cartoon versions of real people she's always known.

A schoolteacher suffered a stroke that paralyzed the left side of her body, but she insists that her left arm is
not
paralyzed. Once, when I asked her whose arm was lying in the bed next to her, she explained that the limb belonged to her brother.

A librarian from Philadelphia who had a different kind of stroke began to laugh uncontrollably. This went on for a full day, until she literally died laughing.

And then there is Arthur, a young man who sustained a terrible head injury in an automobile crash and soon afterward claimed that his father and mother had been replaced by duplicates who looked exactly like his real parents. He recognized their faces but they seemed odd, unfamiliar. The only way Arthur could make any sense out of the situation was to assume that his parents were impostors.

None of these people is "crazy"; sending them to psychiatrists would be a waste of time. Rather, each of them suffers from damage to a specific part of the brain that leads to bizarre but highly characteristic changes in behavior. They hear voices, feel missing limbs, see things that no one else does, deny the obvious and make wild, extraordinary claims about other people and the world we all live in. Yet for the most part they are lucid, rational and no more insane than you or I.

Although enigmatic disorders like these have intrigued and perplexed physicians throughout history, they are usually chalked up as curiosities— case studies stuffed into a drawer labeled "file and forget." Most neurologists who treat such patients are not particularly interested in explaining these odd behaviors. Their goal is to alleviate symptoms and to make people well again, not necessarily to dig deeper or to learn how the brain works. Psychiatrists often invent ad hoc theories for curious syndromes, as if a bizarre condition requires an equally bizarre explanation. Odd symptoms are blamed on the patient's upbringing (bad thoughts from childhood) or even on the patient's mother (a bad nur−turer).
Phantoms in the Bruin
takes the opposite viewpoint. These patients, whose stories you will hear in detail, are our guides into the inner workings of the human brain—yours and mine. Far from being curiosities, these syndromes illustrate fundamental principles of how the normal

human mind and brain work, shedding light on the nature of body image, language, laughter, dreams, depression and other hallmarks of human nature. Have you ever wondered why some jokes are funny and others are not, why you make an explosive sound when you laugh, why you are inclined to believe or disbelieve in God, and why you feel erotic sensations when someone sucks your toes? Surprisingly, we can now begin to provide scientific answers to at least some of these questions. Indeed, by studying these patients, we can even address lofty "philosophical" questions about the nature of the self: Why do you endure as one person through space and time, and what brings about the seamless unity of subjective experience? What does it mean to make a choice or to will an action? And more generally, how does the activity of tiny wisps of protoplasm in the brain lead to conscious experience?

Philosophers love to debate questions like these, but it's only now becoming clear that such issues can be tackled experimentally. By moving these patients out of the clinic and into the laboratory, we can conduct experiments that help reveal the deep architecture of our brains. Indeed, we can pick up where Freud left off, ushering in what might be called an era of experimental epistemology (the study of how the brain represents knowledge and belief) and cognitive neuropsychiatry (the interface between mental and physical disorders of the brain), and start experimenting on belief systems, consciousness, mind−body interactions and other hallmarks of human behavior.

9

I believe that being a medical scientist is not all that different from being a sleuth. In this book, I've attempted to share the sense of mystery that lies at the heart of all scientific pursuits and is especially characteristic of the forays we make in trying to understand our own minds. Each story begins with either an account of a patient displaying seemingly inexplicable symptoms or a broad question about human nature, such as why we laugh or why we are so prone to self−deception. We then go step by step through the same sequence of ideas that I followed in my own mind as I tried to tackle these cases. In some instances, as with phantom limbs, I can claim to have genuinely solved the mystery. In others—as in the chapter on God—the final answer remains elusive, even though we come tantalizingly close. But whether the case is solved or not, I hope to convey the spirit of intellectual adventure that accompanies this pursuit and makes neurology the most fascinating of all disciplines. As Sherlock Holmes told Watson, "The game is afoot!"

Consider the case of Arthur, who thought his parents were impostors. Most physicians would be tempted to conclude that he was just crazy,

and, indeed, that is the most common explanation for this type of disorder, found in many textbooks. But, by simply showing him photographs of different people and measuring the extent to which he starts sweating (using a device similar to the lie detector test), I was able to figure out exactly what had gone wrong in his brain (see chapter 9). This is a recurring theme in this book: We begin with a set of symptoms that seem bizarre and incomprehensible and then end up—at least in some cases—with an intellectually satisfying account in terms of the neural circuitry in the patient's brain. And in doing so, we have often not only discovered something new about how the brain works but simultaneously opened the doors to a whole new direction of research.

But before we begin, I think it's important for you to understand my personal approach to science and why I am drawn to curious cases. When I give talks to lay audiences around the country, one question comes up again and again: "When are you brain scientists ever going to come up with a unified theory for how the mind works? There's Einstein's general theory of relativity and Newton's universal law of gravitation in physics.

Why not one for the brain?"

My answer is that we are not yet at the stage where we can formulate grand unified theories of mind and brain. Every science has to go through an initial "experiment" or phenomena−driven stage—in which its practitioners are still discovering the basic laws—before it reaches a more sophisticated theory−driven stage.

Consider the evolution of ideas about electricity and magnetism. Although people had vague notions about lodestones and magnets for centuries and used them both for making compasses, the Victorian physicist Michael Faraday was the first to study magnets systematically. He did two very simple experiments with astonishing results. In one experiment—which any schoolchild can repeat—he simply placed a bar magnet behind a sheet of paper, sprinkled powdered iron filings on the surface of the paper and found that they spontaneously aligned themselves along the magnetic lines of force (this was the very first time anyone had demonstrated the existence of fields in physics). In the second experiment, Faraday moved a bar magnet to and fro in the center of a coil of wire, and, lo and behold, this action produced an electrical current in the wire.

These informal demonstrations—and this book is full of examples of this sort—had deep implications:1 They linked magnetism and electricity for the first time. Faraday's own interpretation of these effects remained qualitative, but his experi−

ments set the stage for James Clerk Maxwell's famous electromagnetic wave equations several decades later—the mathematical formalisms that form the basis of all modern physics.

My point is simply that neuroscience today is in the Faraday stage, not in the Maxwell stage, and there is no point in trying to jump ahead. I would love to be proved wrong, of course, and there is certainly no harm in trying to construct formal theories about the brain, even if one fails (and there is no shortage of people who are trying). But for me, the best research strategy might be characterized as "tinkering." Whenever I use this 10

word, many people look rather shocked, as if one couldn't possibly do sophisticated science by just playing around with ideas and without an overarching theory to guide one's hunches. But that's exactly what I mean (although these hunches are far from random; they are always guided by intuition).

I've been interested in science as long as I can remember. When I was eight or nine years old, I started collecting fossils and seashells, becoming obsessed with taxonomy and evolution. A little later I set up a small chemistry lab under the stairway in our house and enjoyed watching iron filings "fizz" in hydrochloric acid and listening to the hydrogen "pop" when I set fire to it. (The iron displaced the hydrogen from the hydrochloric acid to form iron chloride and hydrogen.) The idea that you could learn so much from a simple experiment and that everything in the universe is based on such interactions was fascinating. I remember that when a teacher told me about Faraday's simple experiments, I was intrigued by the notion that you could accomplish so much with so little. These experiences left me with a permanent distaste for fancy equipment and the realization that you don't necessarily need complicated machines to generate scientific revolutions; all you need are some good hunches.2

Another perverse streak of mine is that I've always been drawn to the exception rather than to the rule in every science that I've studied. In high school I wondered why iodine is the only element that turns from a solid to a vapor direcdy when heated, without first melting and going through a liquid stage. Why does Saturn have rings and not the other planets? Why does water alone expand when it turns to ice, whereas every other liquid shrinks when it solidifies? Why do some animals not have sex? Why can tadpoles regenerate lost limbs though an adult frog cannot? Is it because the tadpole is younger, or is it because it's a tadpole? What would happen if you delayed metamorphosis by blocking the action of thyroid hormones (you could put a few drops of thiouracil into the aquarium) so that you ended up with a very old tadpole? Would the geriatric tadpole be able to regenerate a missing limb? (As a schoolboy I made some feeble attempts to answer this, but, to my knowledge, we don't know the answer even to this day.)3

Of course, looking at such odd cases is not the only way—or even the best way—of doing science; it's a lot of fun but it's not everyone's cup of tea. But it's an eccentricity that has remained with me since childhood, and fortunately I have been able to turn it into an advantage. Clinical neurology, in particular, is full of such examples that have been ignored by the "establishment" because they don't really fit received wisdom. I have discovered, to my delight, that many of them are diamonds in the rough.

For example, those who are suspcious of the claims of mind−body medicine should consider multiple personality disorders. Some clinicians say that patients can actually "change" their eye structure when assuming different personas—a nearsighted person becomes farsighted, a blue−eyed person becomes brown−eyed—or that the patient's blood chemistry changes along with personality (high blood glucose level with one and normal glucose level with another). There are also case descriptions of people's hair turning white, literally overnight, after a severe psychological shock and of pious nuns' developing stigmata on their palms in ecstatic union with Jesus. I find it surprising that despite three decades of research, we are not even sure whether these phenomena are real or bogus. Given all the hints that there is something interesting going on, why not examine these claims in greater detail? Are they like alien abduction and spoon bending, or are they genuine anomalies—like X rays or bacterial transformation4—that may someday drive paradigm shifts and scientific revolutions?

I was personally drawn into medicine, a discipline full of ambiguities, because its Sherlock Holmes style of inquiry greatly appealed to me. Diagnosing a patient's problem remains as much an art as a science, calling into play powers of observation, reason and all the human senses. I recall one professor, Dr. K.V.

Thiruvengadam, instructing us how to identify disease by just smelling the patient—the unmistakable, sweetish nail polish breath of diabetic ketosis; the freshly baked bread odor of typhoid fever; the stale−beer stench of scrofula; the newly plucked chicken feathers aroma of rubella; the foul smell of a lung abscess; and 11

the ammonialike Windex odor of a patient in liver failure. (And today a pediatrician might add the grape juice smell of
Pseudomonas
infection in children and the sweaty−feet smell of isovaleric acidemia.) Inspect the fingers carefully, Dr. Thiruvengadam told us, because a small change in the angle between the nail bed and the finger can herald the onset of a malignant lung cancer long before more ominous clinical signs emerge. Remarkably, this telltale sign—clubbing—disappears instantly on the operating table as the surgeon removes the cancer, but, even to this day, we have no idea why it occurs.