A Brief Tour of Human Consciousness: From Impostor Poodles to Purple Numbers

Preface

My goal in writing this book has been to make neuro-science—the study of the brain—more accessible to a broad audience, to “workingmen,” as Thomas Huxley would have said. The overall strategy is to investigate neurological dysfunction caused by a change in a small part of a patient’s brain and ask: Why does this patient display these curious symptoms? What do the symptoms tell us about the workings of the normal brain? Can a careful study of these patients help us explain how the activity of a hundred billion nerve cells in the brain gives rise to all the richness of our conscious experience? I have chosen to focus both on areas in which I have worked directly (such as phantom limbs, synesthesia and visual processing) and ones that have a broad interdisciplinary appeal, in order, ultimately, to bridge the gap that now separates C. P. Snow’s “two cultures”—the sciences and the humanities.

The book emerged from the annual BBC Reith lectures that I delivered in Great Britain in 2003. It was an honor for me to be invited to give these lectures, the first physician/experimental psychologist to do so since they were begun by Bertrand Russell in 1948. In the last five decades these lectures have enjoyed a distinguished place in the intellectual and cultural life of the Western world. I was delighted to accept the invitation, knowing that I would be joining a long list of previous lecturers whose works inspired me as a teenager: Peter Medawar, Arnold Toynbee, J. Robert Oppenheimer, John Galbraith and Russell, to mention only a few. I realized that theirs would be a tough act tofollow, given their towering stature and the pivotal role that many of them played in defining the intellectual ethos of our age. Even more daunting was the requirement that I would have to make the lectures not only interesting to the specialist but also intelligible to the “common people,” thereby fulfilling Lord Reith’s original mission for the BBC. Given the enormous amount of research on the brain, the best I could do was to provide an impressionistic survey rather than try to be comprehensive. In doing this I was worried I might have oversimplified many of the issues involved and so run the risk of annoying some of my specialist colleagues. But as Lord Reith himself once said, “There are some people whom it is one’s duty to annoy!”

Chapter 3 (based on the third lecture) deals with an especially controversial subject, the neurology of artistic experience, “neuro-aesthetics,” that is usually considered off limits by scientists. I take a stab at it just for fun and to indicate how a neuroscientist might approach this problem. I make no apology for the fact that it is speculative. As Peter Medawar said, “all good science begins as an imaginative excursion into what might be true.” Speculation is fine, provided it leads to testable predictions and so long as the author makes it clear when he is merely spec-ulating—skating on thin ice—as opposed to when he’s on solid ground. I have taken pains to preserve this distinction throughout the book, often adding qualifying remarks in what have become extensive endnotes.

There is also a tension in the field of neurology between the “single case study” approach, the intensive study of just one or two patients with a syndrome, and sifting through a large number of patients and doing a statistical analysis. The criticism is sometimes made that it is easy to be misled by single strange cases, but this is nonsense. Most of the syndromes in neurology that have stood the test of time—for example, the major aphasias (language disturbances), amnesia (explored by Brenda Milner, Elizabeth Warrington, Larry Squire and Larry Weiskrantz), cortical color blindness, neglect, blindsight, “split brain” syndrome (commissurotomy), etc.—were initially discovered by a careful study of single cases, and I don’t know of even one that was discovered by averaging results from a large sample. The best strategy, in fact, is to begin by studying individual cases and then to make sure that the observations are reliably repeatable in other patients. This is true for a majority of findings described here, such as phantom limbs, the Capgras (impostor) delusion, synesthesia and neglect. The findings are remarkably consistent across patients and have been confirmed in several laboratories.

Many colleagues and students often ask me when I became interested in the brain and why. It is not easy to trace the lineage of one’s interests, but I’ll give it a shot. I have been interested in science from about the age of eleven. I remember being a somewhat lonely child and socially awkward—although I did have one very good science playmate in Bangkok: Somthau (“Cookie”) Sucharitkul. I always felt companioned by Nature and perhaps science was my “retreat” from the social world with all its arbitrariness and mind-numbing conventions. I spent a lot of time collecting seashells and geological specimens and fossils. I enjoyed dabbling in ancient archaeology, cryptography (the Indus script), comparative anatomy and palaeontology; I found it endlessly fascinating that the tiny bones inside our ears, which we mammals use for amplifying sounds, had originally evolved from the jawbones of reptiles. As a schoolboy I was passionate about chemistry and often mixed chemicals just to see what would happen (a burning piece of magnesium ribbon could be plunged into water—it would continue to burn underwater by extracting the oxygen from H₂O). Another passion was biology. I once tried placing various sugars, fatty acids and individual amino acids inside the “mouths” of Venus flytraps to see what triggered them to stay shut and secrete digestive enzymes. And I did an experiment to see if ants would hoard and consume sac-charin—showing the same fondness for it as they do for sugar. Would the saccharin molecule “fool” their taste buds the same way it fools ours?

All these pursuits, Victorian in inspiration, are quite remote from the neurology and psychophysics I specialize in now. Yet those childhood preoccupations must have left a mark that profoundly influences my adult personality and my style of doing science. While engaged in such pursuits, I felt that I was in my own private playground, my own parallel universe inhabited by Darwin and Cuvier and Huxley and Owen and William Jones and Champollion. For me these people were more alive than most “real” people I knew. Perhaps this escape into my own private world made me feel special rather than isolated, “weird” or different. It allowed me to rise above the tedium and monot-ony—the humdrum existence that most people call a normal life—to a place where, to quote Russell, “one at least of our nobler impulses can escape from the dreary exile of the actual world”.

Such an escape is especially encouraged at the University of California, San Diego, an institution that is both venerable and vibrantly modern. Its neuroscience program was recently ranked number one in the country by the National Academy of Sciences. If you include the Salk Institute and Gerry Edelman’s Neurosciences Institute, there is a higher concentration of eminent neuroscientists in La Jolla’s “neuron valley” than anywhere else in the world. I can't think of a more stimulating environment for anyone interested in the brain.

Science is most fun when it is still in its infancy, when its practitioners are still driven by curiosity and it hasn’t become “professionalized” into just another nine-to-five job. Unfortunately this is no longer true for many of the most successful areas of science, such as particle physics or molecular biology. It is now commonplace to see a paper in Science or Nature cowritten by thirty authors. For me this takes some of the joy out of it (and I imagine it does for the authors too). This is one of two reasons I instinctively gravitate toward old-fashioned Geschwindian neurology, where it is still possible to ask naive questions starting from first principles—the kinds of very simple questions that a schoolboy might ask but are embarrassingly hard for experts to answer. It’s a field where it’s still possible to do Faraday-style research and come up with surprising answers. Indeed, many of my colleagues and I see it as an opportunity to revive the golden age of neurology, the age of Charcot, Hughling Jackson, Henry Head, Luria and Goldstein.

The second reason I chose neurology is more obvious; it’s the same reason you picked up this book. As human beings we are more curious about ourselves than about anything else, and this is a research enterprise that takes you right into the heart of the problem of who we are. I got hooked on neurology after examining my very first patient in medical school. He was a man with a pseudo-bulbar palsy (a kind of stroke), who alternately laughed and wept uncontrollably every few seconds. It struck me as an instant replay of the human condition. Were these just mirthless joy and crocodile tears, I wondered? Or was he actually feeling alternately happy and sad, the same way a manic-depressive might, but on a compressed timescale?

We will be considering many such questions throughout the book: What causes phantom limbs? How do we construct a body image? Are there artistic universals? What is a metaphor? Why do some people see musical notes as colored? What is hysteria? Some of these questions I will answer, but the answers to the others remain tantalizingly elusive, such as the big question: What is consciousness? But whether I answer them or not, if this book at least whets your appetite to learn more about this fascinating field, it will have served its purpose. Endnotes, a glossary, a bibliography, and an index are provided at the end for the benefit of those who wish to probe these topics more deeply. As my colleague Oliver Sacks said of one of his books: “The real book is in the endnotes, Rama.”

I would like to dedicate this work to the patients who volunteered to endure hours of testing at our center. I have often learned more from my conversations with them, despite their damaged brains, than from my learned colleagues.