SPEECH AND BRAIN-MECHANISMS הקדמה

begin with what is called a thought. A succession of nerve impulses then flows out from my brain along the nerves in such a pattern that the appropriate muscles contract, while others relax, and I speak. An idea has found expression in electrical energy, movement, vibrations in the air. The boundary which separates philosophy from neurophysiology and physics has been crossed!

When that sound reaches your ear drums it is converted again into nerve impulses that are conducted along your auditory nerves and into your brain. This stream of nerve impulses results in a secondary mental proposition which resembles, but is far from being identical with, that of the speaker. It is a new perception. Again that strange brain-mind frontier has been crossed—crossed twice by each utterance!

Now, you may well wish to debate with me whether or not there is any boundary between nerve impulse and the mental state of a conscious person. And, furthermore, you might add that a neurophysiologist should confine his attention to neurone mechanisms, since he is only a physiologist after all. And yet in a discussion of speech he can hardly avoid consideration of this problem, and we shall return to it presently. Let me now get back on firmer ground where we can discuss the anatomy and physiology of the human brain briefly and simply.

B. Material

The material for these discussions is drawn from study of the patients in an active neurosurgical practice. During the past ten years my associate and co-author, Dr. Lamar Roberts, and I have been studying problems of speech and of brain dominance—a task to which I had turned somewhat earlier with the help of Dr. Preston Robb (1946).* Now Dr. Roberts has collected and reviewed all of the accumulated material. Many patients came to us seeking a cure for focal cerebral seizures which had been caused by earlier injury, infection, or anoxia of the brain. The few who seemed suitable were selected for

* We owe much to our associates in the Montreal Neurological Institute. They have aided us in the organization of studies in clinical physiology. Particularly we thank Herbert Jasper, Professor of Experimental Neurology; Dr. Brenda Milner, clinical psychologist; and Mr. Robert Sparks, speech therapist. Most of all, we are indebted to the intelligent and forbearing patients who have helped us to understand many things in the operating room and out of it.

BRAIN ACTIVITY—NORMAL AND EPILEPTIC

operation. The cases used in this sudy are chosen from that group.

Local anaesthesia was used during the operations (osteoplastic craniotomy). This does away with the pain of the procedure and yet leaves the brain normally active after a segment of the skull has been cut and temporarily turned back and the surface of the brain thus exposed. An operation is described in Chapter VII. Since the patients were talking and fully conscious during the procedures, it was possible to discover what parts of the cortex were devoted to the speech function.

We have reviewed 273 such operations upon the dominant hemisphere and an equal number on the opposite side for the purpose of this study, and Dr. Roberts has carried out a special series of speech examinations on seventy-two of the patients. The therapeutic purpose, in each case, was to remove areas of abnormal brain which were responsible for these attacks, without touching parts that were normal or too precious to be forfeited. Periodic follow-up studies show that such operations have stopped the attacks in about fifty per cent of the cases and made the attacks easier to control by medicine in others.

So much for clinical medicine. The problems of epilepsy and the anatomy and physiology of the human brain have been discussed elsewhere and our evidence summarized.* But it may serve a useful purpose to say a word here about activity in the normal brain and about the sudden abnormal activity that occurs from time to time in the brain of those who are subject to epileptic seizures.

C. Brain activity — normal and epileptic

The brain (Fig. III-i on p. 40) is the convoluted organ which fills the great cavity of the skull. It is composed of nerve cells or ganglion cells, each provided with tail-like nerve fibers or expansions. Each living nerve cell is capable of developing energy that is propagated, as an electric current, along its own expansions. The expansions are insulated except at their endings. At the endings there are synapses across which enough energy can be communicated by a chemical process to the body of another nerve cell to fire off energy in it. Thus, further conduction of electric potentials passes through expansions of the second cell, and so by a

* Penfield and Rasmussen (1950); also Penfield and Jasper (1954).

INTRODUCTION

succession of little activations a stream of impulses passes from one ganglion cell to another and another as determined, no doubt, by complicated facilitations and inhibitions.

It is said that there are ten billion nerve cells (ganglion cells) within the human brain, and each probably has some capacity of generating energy within itself. In addition to these there are even more neuroglial cells which seem to support and nourish and insulate the nerve cells and their branching fibers.

The business of the brain is carried out by the passage of nervous impulses from ganglion cell to ganglion cell in an orderly and controlled manner. The impulses pass quickly along the insulated nerve fibers like an electrical current, while passage across the synapses to successive nerve cells is accomplished by a somewhat slower chemical process. The cell bodies are collected together forming gray matter, and the nerve fibers which conduct the currents compose the white matter. As long as the gray matter is normal, the energy of the nerve cells is employed only in the coordinated functional mechanisms of the brain. But if some area is injured by disease or pressure or lack of oxygen, the gray matter, although it may continue to function, may do so with abnormal additions of its own. There seems to be a defect in the regulating mechanisms which normally limit excessive discharge. Thus, sometimes months or years after injury, an abnormal area “ripens” slowly into a self-discharging electrochemical unit. This is called an epileptogenic focus.

In such an area or focus, excess electrical energy is formed and so, from time to time, unruly mass-discharges may be released. Such an explosive discharge produces an epileptic fit. The fit is large or small, depending upon the extent and intensity of discharge and the position of the gray matter involved. Consequently, the subject may suddenly make aimless movements over which he has no control, or he may have strange sensations or little dreams or memories. From one point of view these seizures are experiments carried out by disease upon the brain. As each attack unfolds, it may demonstrate to the watchful observer the position of the abnormality and also the functional uses of the area involved.

But (alas for the patient!) nature’s experiment often turns into a grim tragedy. The attack, which begins as a small one, may

BRAIN ACTIVITY—NORMAL AND EPILEPTIC

spread to other areas and increase in severity until there is a maximum discharge. Then he has what people call an epileptic fit, a grand mal—falling unconscious with every muscle contracting, groaning, and perhaps frothing at the mouth. Thus, from earliest times epilepsy has been a curse to the epileptic. But when the discharge was small, nature’s experiment has also been a teacher to observant physicians, and it still has much to teach us.

D. The messenger and the interpreter of consciousness

Hippocrates, the father of medicine, writing in the 5th century before Christ, made some thrilling observations on brain function. They are to be found in a medical lecture devoted to epilepsy. The affliction was then called the sacred disease *

Let Hippocrates’ words set the stage for our discussion of the brain and the mind: “Some people say,” he wrote, “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 the brain alone, arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, griefs 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 the messenger. For when a man draws breath into himself, the air first reaches the brain, and so is dispersed through the rest of the body, though it leaves in the brain its quintessence, and all that it has of intelligence and sense. . . . Wherefore I assert that the brain is the interpreter of consciousness.”

You may quarrel with his conception of the way in which the brain takes energy from the air, but his reference to the brain-mind relation is magnificent. “To consciousness the brain is the messenger.” And again, “The brain is the interpreter of consciousness.” So it is with speech. To the speaker the brain becomes “the messenger,” and for the listener the brain serves as the “interpreter.” The message is a sequence of words.

INTRODUCTION

E. The brain and the mind

It was pointed out above that if there is a frontier between mind and brain, it is crossed twice by each utterance during a lecture. Something seems to pass from the speaker’s mind to his brain and from the listener’s brain to his mind. That is assuming, of course, that the listener listens, and there is no assumption in the whole field of education that is so frequently false as this assumption! In any case, when the listener does perceive the meaning of what is said, the record is laid down in some sort of ganglionic pattern—not the speaker’s proposition necessarily, but the listener’s perception of it. For a short time the listener can still reactivate his perception voluntarily. When he does so the frontier is crossed again. After a period of time it is forgotten—lost perhaps to voluntary recall. But the record remains there permanently, nonetheless, ready to be used as a flash-back for the purpose of comparison and interpretation. The nature of this record of consciousness and the mechanism of its re-employment will be discussed in Chapter III.

Let us consider the brain-mind relationship briefly. This is a problem to which a psychologist must turn his attention if he is concerned with psychology. It is a frontier toward which the religious thinker has made many an expedition, carrying with him a beloved guide-book. It is a boundary which, as some philosophers explain it, does not exist at all. But for the neurophysiologist there is a working boundary that does exist. Physiological methods bring him nearer and nearer to it. But he comes to an impasse, and beyond that impasse no present-day method can take him. If he should state that nerve impulses moving in certain patterns are one and the same thing as mind, he accomplishes little for his future work except to deprive himself of a useful working terminology.

Any man who adopts the dualistic terminology speaks of two elements in a living conscious human being: a body and a soul, a brain and a mind, electrical energy conducted through the integrating pathways of the cerebral hemispheres and conscious thought, a living machine and a spirit. However it is expressed, he must think either of a parallelism or a back and forth relationship.

THE BRAIN AND THE MIND

The dualist believes that there is in each individual something additional to the body and its living energy. He may call it a conscious spirit which is the active accompaniment of brain activity and, thus, is present from birth to death except, perhaps, in states of deep sleep and coma. He may also believe that this spirit continues its existence after the death of the body, and that it is somehow one with God. By such belief, he extends the dualism of the individual to a dualism of the universe. The time has passed when the church need necessarily look upon intellectualism as hostile to faith. These concepts of the spirit, and of God, are the things a scientist may believe. But it is what has been called an act of faith. He may organize his life and his work accordingly. But, whatever his inward belief may be, he must recognize that there are no methods in science by which he can test or verify these hypotheses, and that, therefore, his faith in such matters carries with it no greater stamp of authority than that of any other thinking person in any other walk of life.

The need, which many scientists feel, of working with the dual concepts of mind and body was expressed by the distinguished anatomist C. Judson Herrick (1955) as follows:

“The mind-body problem,” he wrote, “will never be solved by ignoring the troublesome factors, either those of spirit or of matter. The enquiry cannot be limited to either the conscious or the unconscious factors, because what we are looking for is the relation between the two. . . . Traditional materialism (the ‘crude’ variety) and classical spiritualism (or, more reputably, ‘idealism’) both involve neglect of a vast wealth of human experience, including common sense and refined scientific knowledge. We cannot choose between materialism and spiritualism. We must have both.”

But two other general hypotheses have been employed: First, there is the point of view, once so persuasively taught by Bishop Berkley, that matter does not exist except insofar as it is conceived in the mind of man or in the mind of God.

Secondly, there is the contrary point of view described as materialism. For those who adhere to this belief, there is no spirit, and the mind of man is to be explained completely by the mechanisms of the brain.

More recently there is a third approach to this matter—a

INTRODVCTION

philosophical approach—which was expressed by Gilbert Ryle (1950) as follows: “The umbrella-titles of ‘Mind’ and ‘Matter’ obliterate the very differences that ought to interest us. Theorists should drop both these words. ‘Mind’ and ‘Matter’ are echoes from the hustings of philosophy, and prejudice the solutions of all problems posed in terms of them.”

The pupils of Ivan Pavlov hope that the conditioned reflexes, which he showed to be so important in some of the learning processes of animals, may yet serve the purposes of a materialistic explanation of the mind. The conditioned reflex enables the animal to adjust to its environment, in part at least, and it is obvious that this would be consistent with the philosophy of Marx, so popular in the Soviet Union today. It is interesting that at present, a most important part of the research of physiologists in that country is devoted to conditioned reflexes. It is good work but the problem is not yet solved.

Perhaps, as Lord Adrian has pointed out, the difficulty will eventually be “solved by some enlargement of the boundaries of natural science” and the appearance of a new psychology.

We are trying to create that enlargement today, but we must not be too impatient in our desire to complete the quest. After all, it is the “revelation of the mystery which was kept secret since the world began”* that we are seeking.

Aristotle pointed out the inconsistency of psychologists in the 4th century B.C., saying, “They place the soul in the body and attach it to the body without trying in addition to determine the reason why, or the condition of the body under which such attachment is produced.”f

Theorists, as Ryle proposes, may be able to give up a dualistic terminology. But biologists are not theorists. And there is no place in scientific medicine for the unprovable hypothesis. We must be content to study man and animal by the scientific method, using the language of “busy common sense.” This is the language of dualism.

We have at present no basis for a scientific explanation of the brain-mind relationship. We can only continue to study the brain without philosophical prejudice. And if the day should ever dawn

* Romans 16:25.

f Be Anima I 3, 22-23 (Wallace translation).

THE BRAIN AND THE MIND

when scientific analysis of body and brain solves the “mystery,” all men who have sought the truth in all sincerity will rejoice alike: the professing materialist and the dualist, the scientist and the philosopher, the agnostic and the convinced worshipper. Surely none need fear the truth.

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