hide captionEven basic sensory maps in the brain can be remapped in a matter of months, says neurologist V.S. Ramachandran.
Even basic sensory maps in the brain can be remapped in a matter of months, says neurologist V.S. Ramachandran.
Dr. V.S. Ramachandran is a neurologist and professor at the University of California, San Diego, who studies the neural mechanisms underlying human behaviors. He has written several books about unlocking the mysteries of the human brain.
In his latest, The Tell-Tale Brain, Ramachandran describes several neurological case studies that illustrate how people see, speak, conceive beauty and perceive themselves and their bodies in 3-D space.
Take, for example, the clinical phenomenon known as the "phantom limb." In the majority of cases where people have lost limbs, they continue to vividly feel the presence of the missing limb. Chronic phantom pain — which strikes roughly two-thirds of patients who have had a limb removed — can become so severe that patients seriously contemplate suicide.
Where Phantom Limb Pain Originates
Several years ago, Ramachandran proposed that phantom limb pain might be caused by changes in the brain — not, as most people thought, in the peripheral nerves near the phantom limb.
W.W. Norton & Company
The Tell-Tale Brain By V.S. Ramachandran Hardcover, 357 pages W.W. Norton & Co. List Price: $26.95
"[It] was based on an idea that there's a complete map of the body's surface on the surface of the brain," he tells Fresh Air's Dave Davies. "So every point on the body's surface has a corresponding point in the brain. Now the curious thing about this map is, even though it's continuous, the face area of the map is right next to the hand area instead of being near the neck where it should be."
Ramachandran suspected that once an arm was amputated, the area in the brain mapped to that arm was deprived of sensory inputs it was used to receiving — and became hungry for new sensations.
If that was true — and if the face area of the brain map invaded the territory corresponding to the hand area of the brain map — touching the face would activate the sensations in the hand area of the brain. Patients would then feel pain on their bodies.
Ramachandran tested his theory by blindfolding patients so that they wouldn't know where he was touching them — and then touched various parts of the body. Sure enough, when touching a patient's face on the same side as an amputated limb, the patient reported that he could feel the sensation in his phantom missing limb. What this proved, he explains, is that the brain is constantly remapping itself as we age.
"What we were all taught as medical students a decade or two ago is that connections in the fetal brain are fixed during infancy or fetal life by genes, and then as you grow into adulthood, the maps crystallize and are there permanently," he says. "But we are finding that this is not true. Even the basic sensory map in the brain gets completely reorganized in a matter of weeks. This challenges the dogma that all medical students are raised with that no new connections or pathways can emerge in the adult brain. That was news 10 or 15 years ago. Now it's widely accepted."
How To Unlearn Phantom Pain
After realizing that phantom limb pain originated in the brain — and that the brain could be remapped — Ramachandran realized he needed to trick patients' brains into unlearning the pain associated with their phantom limbs.
"We call this phenomenon learned pain or learned paralysis," he says. "The question is: Can you unlearn the pain or paralysis by allowing the brain to send a command to the phantom and have the phantom move — or appear to move — in response to the command. But how do you do that? The guy doesn't have an arm. How do you make the arm appear to move?"
hide captionIn one experiment, Ramachandran used a mirror and a cardboard box to perform the first "successful amputation of a phantom limb."
The Center for Brain and Cognition, UCSD
The answer, Ramachandran discovered, was a simple $5 mirror box which he propped up on a table parallel to a patient's nose. The patient put his phantom limb on the nonreflecting side of the mirror and his normal arm on the reflecting side of the mirror. When the patient then looked at the reflecting side, it appeared as if the phantom limb had returned. (It was, in fact, a reflection of the patient's existing arm.)
"If the patient then starts moving his hand, clapping his hand or conducting an orchestra or waving goodbye while looking in the mirror, he's going to see the mirror reflection of the normal hand superposed on the phantom, moving in command with the command sent to the phantom arm," says Ramachandran. "So you're going to get the visual illusion that the phantom limb is obeying the command."
Though patients know intellectually that their phantom limbs have not returned, they are able to successfully trick their brains into thinking that their limbs have returned.
"It not only looks like it's there, it feels like it's there," says Ramachandran. "Patients say, 'When I move my normal hand, the phantom arm looks like it's moving. When I open the normal fist, the phantom hand — whose fist I could not open for months — suddenly feels as if it is opening as a result of the visual feedback, and the painful cramp goes away.' This is a striking example of modulation of pain signals by vision."
Dr. V.S. Ramachandran, called the "Marco Polo of neuroscience" by Richard Dawkins, is the author of several books on the brain, including Phantoms in the Brain: Probing Mysteries of the Human Mind and A Brief Tour of Human Consciousness: From Impostor Poodles to Purple Numbers. He gave the 2003 BBC Reith Lectures and has published more than 180 papers in scientific journals including Nature and Science.
Excerpt: 'The Tell-Tale Brain'
by V.S. Ramachandran
W.W. Norton & Company
The Tell-Tale Brain By V.S. Ramachandran Hardcover, 357 pages W.W. Norton & Co. List Price: $26.95
For the past quarter century I have had the marvelous privilege of being able to work in the emerging field of cognitive neuroscience. This book is a distillation of a large chunk of my life's work, which has been to unravel — strand by elusive strand — the mysterious connections between brain, mind, and body. In the chapters ahead I recount my investigations of various aspects of our inner mental life that we are naturally curious about. How do we perceive the world? What is the so-called mind-body connection? What determines your sexual identity? What is consciousness? What goes wrong in autism? How can we account for all of those mysterious faculties that are so quintessentially human, such as art, language, metaphor, creativity, self-awareness, and even religious sensibilities? As a scientist I am driven by an intense curiosity to learn how the brain of an ape — an ape! — managed to evolve such a godlike array of mental -abilities.
My approach to these questions has been to study patients with damage or genetic quirks in different parts of their brains that produce bizarre effects on their minds or behavior. Over the years I have worked with hundreds of patients afflicted (though some feel they are blessed) with a great diversity of unusual and curious neurological disorders. For example, people who "see" musical tones or "taste" the textures of everything they touch, or the patient who experiences himself leaving his body and viewing it from above near the ceiling. In this book I describe what I have learned from these cases. Disorders like these are always baffling at first, but thanks to the magic of the scientific method we can render them comprehensible by doing the right experiments. In recounting each case I will take you through the same step-by-step reasoning — occasionally navigating the gaps with wild intuitive hunches — that I went through in my own mind as I puzzled over how to render it explicable. Often when a clinical mystery is solved, the explanation reveals something new about how the normal, healthy brain works, and yields unexpected insights into some of our most cherished mental faculties. I hope that you, the reader, will find these journeys as interesting as I did.
Readers who have assiduously followed my whole oeuvre over the years will recognize some of the case histories that I presented in my previous books, Phantoms in the Brain and A Brief Tour of Human Consciousness. These same readers will be pleased to see that I have new things to say about even my earlier findings and observations. Brain science has advanced at an astonishing pace over the past fifteen years, lending fresh perspectives on — well, just about everything. After decades of floundering in the shadow of the "hard" sciences, the age of neuroscience has truly dawned, and this rapid progress has directed and enriched my own -work.
The past two hundred years saw breathtaking progress in many areas of science. In physics, just when the late nineteenth-century intelligentsia were declaring that physical theory was all but complete, Einstein showed us that space and time were infinitely stranger than anything formerly dreamed of in our philosophy, and Heisenberg pointed out that at the subatomic level even our most basic notions of cause and effect break down. As soon as we moved past our dismay, we were rewarded by the revelation of black holes, quantum entanglement, and a hundred other mysteries that will keep stoking our sense of wonder for centuries to come. Who would have thought the universe is made up of strings vibrating in tune with "God's music"? Similar lists can be made for discoveries in other fields. Cosmology gave us the expanding universe, dark matter, and jaw-dropping vistas of endless billions of galaxies. Chemistry explained the world using the periodic table of the elements and gave us plastics and a cornucopia of wonder drugs. Mathematics gave us computers — although many "pure" mathematicians would rather not see their discipline sullied by such practical uses. In biology, the anatomy and physiology of the body were worked out in exquisite detail, and the mechanisms that drive evolution finally started to become clear. Diseases that had literally plagued humankind since the dawn of history were at last understood for what they really were (as opposed to, say, acts of witchcraft or divine retribution). Revolutions occurred in surgery, pharmacology, and public health, and human life spans in the developed world doubled in the space of just four or five generations. The ultimate revolution was the deciphering of the genetic code in the 1950s, which marks the birth of modern biology.
By comparison, the sciences of the mind — psychiatry, neurology, psychology — languished for centuries. Indeed, until the last quarter of the twentieth century, rigorous theories of perception, emotion, cognition, and intelligence were nowhere to be found (one notable exception being color vision). For most of the twentieth century, all we had to offer in the way of explaining human behavior was two theoretical edifices—Freudianism and behaviorism — both of which would be dramatically eclipsed in the 1980s and 1990s, when neuroscience finally managed to advance beyond the Bronze Age. In historical terms that isn't a very long time. Compared with physics and chemistry, neuroscience is still a young upstart. But progress is progress, and what a period of progress it has been! From genes to cells to circuits to cognition, the depth and breadth of today's neuroscience—however far short of an eventual Grand Unified Theory it may be—is light-years beyond where it was when I started working in the field. In the last decade we have even seen neuroscience becoming self-confident enough to start offering ideas to disciplines that have traditionally been claimed by the humanities. So we now for instance have neuroeconomics, neuromarketing, neuroarchitecture, neuroarcheology, neurolaw, neuropolitics, neuroesthetics (see Chapters 4 and 8), and even neurotheology. Some of these are just neurohype, but on the whole they are making real and much-needed contributions to many fields.
As heady as our progress has been, we need to stay completely honest with ourselves and acknowledge that we have only discovered a tiny fraction of what there is to know about the human brain. But the modest amount that we have discovered makes for a story more exciting than any Sherlock Holmes novel. I feel certain that as progress continues through the coming decades, the conceptual twists and technological turns we are in for are going to be at least as mind bending, at least as intuition shaking, and as simultaneously humbling and exalting to the human spirit as the conceptual revolutions that upended classical physics a century ago. The adage that fact is stranger than fiction seems to be especially true for the workings of the brain. In this book I hope I can convey at least some of the wonder and awe that my colleagues and I have felt over the years as we have patiently peeled back the layers of the mind-brain mystery. Hopefully it will kindle your interest in what the pioneering neurosurgeon Wilder Penfield called "the organ of destiny" and Woody Allen, in a less reverential mood, referred to as man's "second favorite organ."
Reprinted from The Tell-Tale Brain by V.S. Ramachandran by arrangement with W.W. Norton & Co. Copyright 2011 by V.S. Ramachandran.