CHAPTER 1
Sherringtonian Alternatives — Two Fundamental Elements or Only One?
My professional career was shaped, I suppose, in the neurophysiological laboratory of Professor Sherrington at Oxford. Eventually it was continued in the wards and operating rooms of the Montreal Neurological Institute. Other preoccupations were many and varied, but beneath them all was the sense of wonder and a profound curiosity about the mind. My planned objective, as I turned from studying the animal brain to that of man, was to come to understand the mechanisms of the human brain and to discover whether, and perhaps how, these mechanisms account for what the mind does.
My teacher, Sir Charles Sherrington, received the Nobel Prize for his studies of reflexes and his analysis of the integrative action of the nervous system. His interest had been focused largely on the inborn reflexes, but, on retiring from the Chair of Physiology at Oxford in 1935, at the age of seventy-eight, he turned from animal experimentation to a scholarly and philosophical consideration of the brain and the mind of man.
In the end, he could only say that "we have to regard the relation of mind to brain as still not merely unsolved, but still devoid of a basis for its very beginning." In June 1947, he wrote a foreword to his book, The Integrative Action of the Nervous System, which was then being republished in his honor by the Physiological Society. The last paragraph of his foreword expresses his conclusion of it all:
That our being should consist of two fundamental elements offers, I suppose, no greater inherent improbability than that it should rest on one only.
It is a quarter of a century since Sherrington wrote these words. We have learned a good deal about man since then, and it is exciting to feel, as I do, that the time has come to look at his two hypotheses, his two "improbabilities." Either brain action explains the mind, or we must deal with two elements.
Perhaps we may take a step toward understanding, if we strive to fit each of the two hypotheses in turn to the physiological evidence that presents itself today. A good scientist is neither a monist nor a dualist while conducting his research. His chosen task is to explain everything he can by critical examination of nature and of the brain, and by planned experimentation. He will account, thus, for what he can about the universe and about man himself, having put his preconceptions out of mind. But he must stop to reconsider, too, and to rationalize from time to time.
Lord Adrian, who shared the Nobel Prize with Sherrington, spoke as a neurophysiologist in 1966 when he said: "As soon as we let ourselves contemplate our own place in the picture, we seem to be stepping outside of the boundaries of natural science." I agree with him; nevertheless, we must step across that boundary from time to time, and there is no reason to assume that critical judgment does not go with us.
Writing this book presents the author with a very exciting challenge. Accepting this, I can only give an account of my own experience, describing it simply for the clinician, the physiologist, the philosopher, and the interested layman, with apologies to each for the fact that I have not written for him separately.
A remarkable body of material has come into my hands and I have stumbled on exciting discoveries. I did summarize the material and I recorded it during and at the close of my professional career. But I turned then with great enthusiasm to authorship of another sort, perhaps unwisely. Perhaps it is one's duty to do more than make a record. In answer, I may plead that I can see it all in more mature perspective after an interval, even in the seventh and eighth decades. Is it an effort, if I may paraphrase Hamlet, to lay a "flattering unction to my soul"?
However that may be, as I turn back now to the material and reconsider a life's experience, I seem to see more clearly and understand a little better. So, I shall give the reader a brief account of this pilgrim's progress. It is a story of stumbling upon unexpected revelations, of consequent puzzlement and misconception, and of reaching higher ground to look out on thrilling new vistas of understanding. In the end I shall draw conclusions that are scientific, and present hypotheses that are obvious. After that, because these data are important in other disciplines of thought, I shall pass on to rationalization and a consideration of man's being from the point of view of a layman, and, as far as I can understand it, the point of view of philosopher and even theologian.
Can the brain explain the man? Can the brain achieve by neuronal action all that the mind accomplishes? The evidence that a clinical physiologist can gather should help to answer these questions in the end.
To see the problem of the nature of the mind more clearly, consider with me this universe of ours in long perspective. It was only after the middle millennia that life appeared — first in unicellular organisms, then gradually in more and more complicated forms, first in the sea and then on the land. It was a very recent event, as seen in this long perspective, when evidence appeared of the individual's self-awareness and purpose. Today man, with his amazing mind and his vastly complicated brain, seeks to understand the universe about him, and even the nature of life and of consciousness.
Physiologists have thrown what light they could on these things from their study of mechanisms within the body and the brain in higher and lower living organisms. They have studied sensation and movement, reflex action, and memory and behavior. Karl Lashley spent thirty years of his industrious life striving to discover the nature of the "memory trace" in the animal brain, beginning with experimental investigations of the rat's brain and ending with the chimpanzee. He was hunting for the engram, the record; that is to say: "the structural impression that psychical experience leaves on protoplasm." He failed to find it and ended by laughing cynically at his own effort and by pretending to question whether, after all, it was possible for animals or even man to learn at all.
But consciousness and the relationship of mind to brain are problems difficult to study in animals. Clinical physicians, on the other hand, in their approach to man, may hope with reason to push on toward an understanding of the physiology of memory and the physical basis of the mind and of consciousness.
CHAPTER 2
To Consciousness the Brain Is Messenger
Hippocrates, the Father of Scientific Medicine, began to teach in the fifth century B.C. on the little Greek island of Cos. In that time, philosophers such as Empedocles and Democritus were proclaiming each his own explanation of the universe and the nature of man. Hippocrates defied what he called the "unproven hypotheses" of the philosophers, and declared that only the study and observation of nature and of man would point the way to truth.
He studied man in health and in disease, making of medicine a science and an art. But he saw in man something beyond any discovery that can be made elsewhere in nature, and thus added a moral code, a religion of medical service. In the oath that he required of his disciples there were such phrases as this: "I will use treatment to help the sick according to my ability and judgment, but never with a view to injury or wrongdoing. ... I will keep pure and holy both my life and my art." Thus, he recognized the moral and the spiritual as well as the physical and the material.
Hippocrates left behind him only a single discussion of the function of the brain and the nature of consciousness. It was included in a lecture delivered to an audience of medical men on epilepsia, the affliction that we still call epilepsy. Here is an excerpt from this lecture, this amazing flash of understanding: "Some people say that the heart is the organ with which we think and that it feels pain and anxiety. But it is not so. Men ought to know that from the brain and from the brain only arise our pleasures, joys, laughter and tears. Through it, in particular, we think, see, hear and distinguish the ugly from the beautiful, the bad from the good, the pleasant from the unpleasant. ... To consciousness the brain is messenger." And again, he said: "The brain is the interpreter of consciousness." In another part of his discussion he remarked, simply and accurately, that epilepsy comes from the brain "when it is not normal."
Actually, his discussion constitutes the finest treatise on the brain and the mind that was to appear in medical literature until well after the discovery of electricity. It was the evidence of conduction of the brain's energy along the nerves of animals that led to the discovery of electricity itself.
In retrospect, it is abundantly clear that Hippocrates came to his- conclusions by listening to epileptic patients when they told him their stories, and by watching them during epileptic seizures. The reader will come to understand, in the pages that follow, that epilepsia still has secrets to reveal. She has much to teach us if we will only listen.
Some of the notes that Hippocrates made after examining his patients were copied and recopied through the centuries. They are models of brevity and insight. Epileptic patients of a certain type, not infrequently, re-live some previous experience in which they see, perhaps, and hear what they have seen and heard at an earlier time in their lives. Realizing, as Hippocrates did, that "epilepsy comes from the brain 'when it is not normal,'" he must have guessed the truth — that the engram of experience is a structured record within the brain.
It was the common understanding in those days that the soul, or consciousness, was located in the heart. For example, four hundred years later, these familiar words appeared in the Christian Gospel according to Luke: "Mary kept all these things and pondered them in her heart." When men did finally abandon the idea that thinking was carried out in the heart, and realized that the brain was the master organ, the words of Hippocrates had long been forgotten. Men thought that the brain acted somehow as a mysterious whole, sending out and receiving spirit messengers in accordance with the teaching of the physician Galen (A.D. 131–201). Long after Galen, came the discovery of animal electricity by Galvani (A.D. 1791), which banished the spirit messengers forever.
We know now that the brain does not act mysteriously, as a simple and uncomplicated whole. It has within it many partly separable mechanisms, each of them activated by the passage of electric currents along insulated nerve fibers. I shall point out presently that there is a specific mechanism that must be active to make consciousness and thought possible.
Can I discuss this mechanism understandably if I leave behind the technical phrase and speak the language of the unspecialized but educated man? I dare say Benjamin Franklin, founder of the American Philosophical Society, explained in easily understood excitement to the first members of that society how it is that electricity passes down the wet string of a kite. I wish I had been there. Perhaps I would have understood the nature of this all-important wonder called electricity. It seems to me that, somehow, it is like the mind in the sense that one cannot assign to the mind a position in space and yet it is easy to see what it does and where it does it.
CHAPTER 3
Neuronal Action within the Brain
Definitions are useful at the beginning of an essay — although the text, in this case, will certainly show them to be inadequate. The mind (or spirit) is, to quote from Webster's Dictionary: "the element ... in an individual that feels, perceives, thinks, wills, and especially reasons."
The brain is the vastly complicated master organ within the body that makes thought and consciousness possible. In its integrative and coordinating action, it resembles in many ways an electrical computer. An individual brain-mechanism is a functional unit that plays a somewhat specialized role in the total integrative action of the brain.
Each nerve cell, or neurone, is capable of developing its own electrical charge. Each has one branch called the axone, among its many branches. The axone carries a current of neuronal impulses outward, away from the cell, to other cells. The arriving impulses stimulate each target cell to flash the message onward, or they check activity in the target cell producing inhibition of cell activity.
The cell bodies are collected together, forming islands, or blankets of gray matter. The branching connections form the white matter. This whole system vibrates, one might say, with an energy that is normally held in disciplined control, like that of a vast symphony orchestra, while millions of messages flash back and forth, to as many functional targets.
However, when some abnormality presents itself within the skull, and becomes a chronic abnormality that irritates the gray matter, it forms a focus of irritation and may cause a recurring disorderly explosion of energy involving many cells at once, like lightning from a miniature thunder cloud. Each time this happens, an epileptic fit comes to some unfortunate victim. The attack varies in outward character according to the function of the gray matter in which the discharge takes place. If it occurs in the cells of the gray matter that forms a part of one of the sensory circuits, a sensation is felt; if it occurs in cells of the motor system, movement follows. Epilepsy, which is the name for the tendency to these attacks, is as old as the history of man. Indeed, it is probably much older, since it attacks animals far more primitive than man.
When the Montreal Neurological Institute opened its doors in 1934, we had available, at last, facilities for studying the human brain as well as for treating its disabilities. I had learned to operate on epileptic patients like those who taught Hippocrates so much. In some cases, we could remove the cause or remove the altered portion of brain in which the epilepsy-producing discharge began.
Our purpose, of course, was always to cure. And the patient, who remained awake and alert through long operations, carried out in the hope of cure, did guide the surgeon's hand. More than that, the patient taught us much in the process.
Since a gentle electric current interferes with the patient's use of a convolution of the brain and sometimes produces involuntary expression of its function, a stimulating electrode could be used to map out the cortex and to identify the convolutions as the patient described his sensations and thoughts. Also, the electrode, if used with discretion, would sometimes reproduce the beginning of the patient's epileptic seizure and, thus, disclose the site of brain irritation. By talking to the patient and by listening to what came into his mind each time the electrode was applied to the cortex, we stumbled upon new knowledge. If we removed convolutions as treatment for the fits, we learned about brain function in another way as soon as the nature of the patient's loss was determined after the operation.
The observations to be presented in the following discussions, Chapters 4 through 9, have been published from time to time with the help of a succession of able associates in the Montreal Neurological Institute, not all of whom are named in the bibliography.
CHAPTER 4
Sensory and Voluntary-Motor Organization
Here, then, is a brief outline of the sensory and motor mechanisms and of some of the inborn reflexes that play roles in the integrative action of the brain of man and other mammals. I hope it may serve as a preparation for some readers and a review or revision for others, before I pass on to the discussion of brain-mechanisms that are more closely related to the action of the mind.
The brain-stem and the spinal cord provide man with inborn reflexes, as they do the other mammals. They regulate such things as muscle tone, maintenance of posture, mechanics of walking, temperature control and sleep-rhythm, breathing, and coughing (see Figure 1).
The cerebral hemispheres that make up the telencephalon, or new brain, grow out of the diencephalon, which may be called the higher brain-stem or old brain. The hemispheres increase in proportional size from the lower vertebrates on up to man. The inflow of nerve impulses carrying pain sensation, for example, passes inwards and upwards through the spinal cord and lower brain-stem to a nucleus of gray matter within the diencephalon. This is the target-gray matter for pain. Pain differs from other forms of sensation since it makes no detour to the cerebral cortex. But the other bundles of fibers carrying sensory impulses that will be converted into discriminatory sensation make important detours. These streams provide information for appreciation of touch, position, vision, hearing, taste, and smell. Each stream comes to a first cellular interruption in the gray matter within the higher brain-stem, but continues on (with the possible exception of smell) in a detour out to a second cellular interruption in the gray matter of the cerebral cortex. From there it returns directly to the target-nucleus of cells within the gray matter of the higher brain-stem.
