Studies in the Osteopathic Sciences
The Physiology of Consciousness: Volume 3
Louisa Burns, M.S., D.O., D.Sc.O.

    It is very evident that it is impossible to define consciousness in any exact sense. It is just as evident that it is impossible to define any primitive conception. Such terms as energy, matter, life, and all other terms applied to simple ideas, are, by that fact impossible of definition, just as the axiom in mathematics is impossible of proof. Consciousness is one of these ideas.

    Yet, while the exact definition of the term is impossible, it is, like other primitive ideas, capable of a certain amount of elucidation. In order to use the term at all with profit, it is necessary to agree upon the application of the term. This must be done, as in the case of other primitive ideas, by the statement of certain relationships between consciousness and other ideas with which we are more or less familiar. It must be recognized that in our inability to exactly define consciousness we are placed in exactly the same position as we are in our inability to define matter or energy or any other primitive idea. We may only explain the use of the word matter, energy, etc., by the statement of the relationship between matter and movement, for example, or between energy, heat and light, and by otherwise expressing relationship. In the same way it becomes possible to understand something, not of the real nature of consciousness, but of its relationship to other phenomena of nature, and especially to other phenomena of physiology and biology.


    Consciousness is a phenomenon associated with the activity of the cells of the cerebral cortex, probably of the external layer. It is associated with the activities of all parts of the cortex, and it is vivid or dim according to the metabolism of these neurons. Consciousness is dim when the metabolism of the cortical neurons is less energetic, and is vivid when the metabolism of the neurons is most energetic. Of the entire extent of the cortex, those areas in which metabolism is most energetic represent their specific energies most vividly in consciousness. Increased activity of the sense areas gives rise to increased vividness in consciousness; increased activity of the motor areas gives rise to an increased sense of power and volition in consciousness. There are infinite gradations in the vividness of consciousness, according to the infinite gradations of neuronic activity. There are infinite variations in the characteristics of consciousness, according to the infinite variations in the relative activity of different neuron groups at different times.

Grades of Consciousness

    All grades of consciousness exist in the factors present at any one time. No consciousness is probably associated with the meager activities of undeveloped neurons, as, for example, the neurons of the visual area of the cortex of the person born blind, while the most vivid consciousness is associated with the activity of neurons often stimulated by incoming sensory and associational impulses. Between these extremes are found almost an infinite variety of grades of consciousness. It is no more possible to establish limits and grades of consciousness, levels of minds above minds, than it is to classify the tints of yesterday’s sunset, or to establish the gradations of twilight during a winter’s evening.

Consciousness and Neurons

    Every factor in consciousness is capable of being expressed in terms of neuronic activity. Every habit of thought and feeling is capable of being expressed in terms of neuronic physiology or morphology. The characteristics of personality are probably due to the relative structural relationships between neuron groups and the physiological activities of the neurons so related. If our knowledge of the physiological processes of the cortical neurons were complete, it should be easy to anticipate not only the manner in which any person would act under certain circumstances, but also how he would feel in so acting. It is not necessary to say that we have as yet no such exact information concerning physiological processes. It is also true that the difficulties in the way of research into the physiology of the cortical neurons are so great that it now seems impossible that the problems associated with the physiology of the cortical neurons should ever be answered.

Stream of Consciousness
    The term “stream of consciousness’ is used. This depends for its forcefulness upon the fact that there is a constantly changing relationship between the relative energies of the different neuron groups. Not only are the different primary sense areas subject to constantly varying stimuli, but the overflow areas are constantly being stimulated by these sensory impulses, and the intermediate areas are, in turn, being stimulated by these and by one another, and so there must at all times be a succession of states of consciousness compelled by the constantly varying conditions and relations of neuronic activity.

    Consciousness is not to be regarded as a force, in any sense of the word. Consciousness is no more a force than the sweetness of sugar, or the pinkness of a rose, or the brightness of the stars, or the beauty of the sunset sky. Indeed, it is not so much a force as sound, since sound waves are really a form of energy; nor as light, since this also is a form of energy. Consciousness is merely a function of the cortical neurons, so far as physiological knowledge is concerned. It is absolutely valueless as a stimulant of physiological activity. But the conditions of the cortical neurons which may affect physiological reactions may, and often do, affect consciousness, and this is the reason why so many people think the mind is the efficient factor in producing the physiological effect. It is the activity of the cortical neurons which produces both the physiological changes and the variations in consciousness.

The Body-mind Controversy

    The idea of the great importance of the control of the mind over the body arose from a misunderstanding of the physiology of the cortical neurons. Much of what is ponderously explained by the effect of the mind over the body is made simple and easily understood when it is recognized that it is not mind, but the cerebral neurons which affect bodily activities. Strength comes, not because of the consciousness of strength, but the consciousness of strength comes because the cortical neurons are stimulated in a certain manner. It is true that such information is not always exact. Often the consciousness of strength may be associated with even a dying condition. This is true of all our sensations; not one of them is to be depended upon absolutely. But so far as we are conscious of anything at all, we are conscious through the activities of the cortical neurons. And while this activity may not give exactly correct information, it is the best we have at present.

Physiological Aspect

    The study of the physiology of consciousness, then, is a study of the physiology of the cortical neurons. Such a study inquires into the effects produced in consciousness by neuronic activity, and also into the relationships between the centers of the nervous system in their effects upon consciousness, either directly or indirectly. The effects of somatic conditions upon the activities of the cortical neurons, the effects of the environmental conditions upon the body itself and thus upon cortical activity, the effects of cortical activity upon the lower nerve centers and thus upon the body itself, and the manner in which relations are formed between the cortical neurons and the external world, all are problems which are associated with the physiology of consciousness.

    The facts and conclusions of this study should be of value to educators, and especially to those who deal with abnormal persons. In this connection the original meaning of the word “doctor” as “teacher” must be suggested.

    In this study it is needful to limit the factors under consideration to the physiological aspects of the problems under consideration. Many very interesting, and perhaps, under other circumstances, very helpful, factors must be eliminated from this frankly physiological study of consciousness. The elimination of these other considerations from this discussion does not imply any denial of their existence. In the study of astronomy no mention is usually made of the “soul of the universe,” or of the marvelous beauties of the nightly sky, or of the ultimate destiny of the stellar system. So, in studying the physiology of consciousness, the philosophical, and esthetic, and idealistic view may be eliminated in the same way as these same views are eliminated in the study of the physics or the chemistry of the physiology of digestion or circulation.

Function of Consciousness
    It seems probable that consciousness is developed pari passu with cephalization—that is, with increasing complexity of reaction to environmental variations, with increasing complexity of neuronic relationships, and with increasing complexity of the environmental factors as affecting the sensorium. Consciousness is of value only as it increases the efficiency of the reactions.

    If the environment of an individual be made larger, as it is by the increased efficiency of the sensory neurons and the neuron groups associated with these, the reactions of the individual must be made more efficient. If intermediate and overflow areas add to the complexity of the reactions possible to any given stimulation, and consciousness is associated with this increasing complexity, only the added efficiency is able to approve the increased metabolic expenses.
Only as the phenomenon of consciousness added to the vigor, and force and efficiency of the race is its existence proved to be worth its price.

Extra-neuronic Consciousness

    This rather materialistic view of consciousness arouses many questions. Are there no other forms of consciousness than those associated with the activity of the cortical neurons? This question is not to be answered from the physiological standpoint. It is not ever safe to hazard negative statements in the absence of absolute proof, and absolute proof is a thing which it is impossible, at present, to secure. If it were possible to catch ideas without any connection with physiological processes, the matter would be solved for ever. Or if it were possible for elements of consciousness never before experienced to become present to any individual, then would the matter be settled, in a certain sense. But neither of these things seems to be possible. The only attempt which is being made along such lines was begun by the Psychical Research Society. The “ghost stories” accumulated by this organization are alike in failing to eliminate the possibility of physiological explanations of the marvelous occurrences. In order to secure evidence of value, the conditions experienced by certain chosen individuals should be related in order; then the number of those experiences which seem to be associated with the occurrence of circumstances outside the realm of the experiences of these persons should be noted. Elements whose association might have led to the conclusions which have part in the so-called psychical information should be eliminated from the final summing up of results and the probabilities of error estimated, together with the chances for coincidence. Such experiments, including many factors, and being performed upon normal persons as well as upon those blind and deaf from birth, should give exact information as to whether (1) consciousness is possible in the absence of physiological activities, and (2) whether ideas are capable of being transmitted without the intermediation of sensory impulses. There is, at present, no evidence that either such condition is present.

Nature of Volition

    The world-old question of the “freedom of the will” arises in connection with the physiological interpretation of consciousness. In physiological terms, volition is the consciousness of the activity of the cortical neurons concerned in producing motor activities, either in the primary motor area, in which the reaction occurs immediately, or in the motor overflow area, in which the memories and probably also certain decisions are stored.

    As to “freedom of choice,” what is it that is meant to be free? The expression of personality is that which is usually understood by freedom of will. If personality means anything in the physiological sense, it means the sum of characteristics, mental and physical; or in other words, individuality is the sum of certain inherited characteristics, plus the variations produced, as these have been subjected to the action of a certain series of environmental variations. From the so-called mental aspect, individuality depends upon the structural relations of the neurons plus the physiological conditions of the neuron systems as they are modified by use and by environmental factors. The only “freedom” desirable, then, is that there shall be no abnormal condition interfering with the passage of nerve impulses from any cortical area to other related cortical centers, and that no impediment shall exist to the activities resulting from the coordination of the nerve impulses through and by the various cortical centers. For certainly no greater efficiency is to be desired than that resulting from the normal activity of normal neurons, acting in accordance with the present sensory stimulation, modified by racial and individual memories and associations. All the freedom needed is found in the activities of normal neurons, in normal bodies, placed in the midst of a normal environment.

    Hesitancy is the consciousness of inhibitory process in the cortical neurons, with simultaneous activity of the neurons of the intermediate areas. Choice is the consciousness of the increased activity of certain neuron groups, often, but not always, motor. Reason is the effect produced in consciousness by the passing of impulses to and from the different intermediate and overflow areas. Judgment is the consciousness of the activity of motor areas, following the process of reasoning, and usually associated with activity of the language centers. Memory is the effect in consciousness of the repeated activity of neuron groups, as these are stimulated from cortical centers.

    Attention is the effect in consciousness of excessive activity of any given cortical area. Marked activity of any cortical area is usually associated with efferent impulses form that center.

    Attention which is called active or volitional is the effect produced in consciousness by the increased metabolism of the cortical neurons of an area subjected to stimulation by the impulses form the intermediate or overflow areas. The sense of volition in attention depends upon the existence of the activity of the cells of the motor areas. The attention called passive is the effect in consciousness of the increased activity of the cells of some primary sense area, resulting from increased stimulation.

    In terms of psychology, the active volition is that which the person himself chooses, as in applying himself to some line of study, though it may be neither interesting nor pleasant. Passive attention is produced by external stimulation of a marked type, as a blow, a loud sound, a bright light, etc.

Consciousness of Personality

    The consciousness of personality depends upon the normal relationship between a series of neuronic events. The activities of the neurons of the anterior intermediate areas are concerned in the coordination of the impulses which relate the individual to his environment, and it is the consciousness aroused by these activities which we call self-consciousness, or the consciousness of one’s own proper place in the midst of things—of his relations to his environment and to his fellow man. With the loss of the functions of these areas the person is not properly oriented to his circumstances. The condition is most conspicuously displayed in senility and in paresis. In both of these conditions, as well as in certain other diseases, the pathological process may affect first the frontal lobes. There is a slow degeneration of the neurons of the cortex, first those more superficial, then the deeper neurons. At first there is not produced any paralysis, nor any pressure symptoms. It often occurs under such conditions that very exact pictures of the effects of loss of function of the anterior association areas are shown. The person so affected loses his sense of relationship with his fellows; he becomes careless of the opinions of other people, is inordinately vain, or considers himself a person of tremendous importance, or of fabulous wealth, or in other ways shows a lack of appreciation of his own proper place. At the same time, he may show as great intelligence in regard to things not personally related to him as ever. In such cases, if death occurs early in the disease, it is usually found that the left frontal cortex is chiefly or alone affected. If death occurs later, it is usually found that these areas show the oldest lesions.

    Since these areas receive the impulses arising from visceral changes, and since the longer tracts carry impulses from almost every other part of the cortex to the frontal lobes, it is evident that this consciousness of personal relation to the environment is capable of being affected by many conditions.

    Probably the impulses from the body itself, including the viscera, are of importance in modifying the consciousness of personality, though this matter is not easily subject to any tests. Under abnormal conditions of visceral disorder the ideas of personality often become changed. A sleep occurring after long or wearying or sleepless days is often followed by a recognizable space of time during which one is unable to orient himself to his surroundings. The same condition is sometimes found after anesthesia or after great pain. In one case there was a period of great pain, followed by unconsciousness, probably associated with a cardiac disturbance. The process of recovery to consciousness was associated with a total loss of personality. The patient described a universe of pain, without personality, simply a whirling of objectless and subjectless pain, which lasted, as she expressed it, for several eternities. Consciousness of herself as suffering pain followed, then came a peculiar sensation as of a body without parts, then consciousness of arms followed a reflex movement, then at once consciousness of the entire body followed. Similar conditions may be associated with nightmare, delirium, and under various abnormal conditions of the cerebral cortex.

Dissociation of Personality

    As a result of certain not very well studied pathological conditions of the cortical neurons a condition called dissociated personality may be produced. This condition has its physiological analogue in the condition of the normal person who is just awaking from a sound sleep. He may be unable to “place” himself for a part of a minute, or even longer.

    The physiological basis for the condition lies, probably, in the interruption of the effect in consciousness normally produced by the constant cortical activity; that is, after unusually sound sleep, such as follows unusual fatigue, but not otherwise abnormal, the cortical neurons probably either fail in assuming their functions with their accustomed facility, or during such sleep their activity is rendered slightly abnormal. The lack of any exact knowledge concerning the metabolism of the cortical neurons during sleep renders it impossible at present to decide which, or whether either, of these possibilities is the true solution of the problem. At any rate, the slightly abnormal failure of the consciousness of personality under such conditions brings the phenomena of dissociated personality into line with the conditions associated with practically normal life and mentality.

    In the presence of shock, or long-continued neurasthenic or hysterical conditions, the activities of the cortical neurons become unbalanced. Certain neuron groups, being acted upon by paralyzing poisons, display great eccentricities of conduct. Certain entire areas of the cortex may become non-functional so far as the production of consciousness is concerned, yet memories may be stored during this stage of non-function of the neurons concerned in consciousness; that is, the hysterical person may be unable to see certain colors or objects placed slightly on one side of the field of vision. Yet after recovery the patient may describe the very object and colors to which he had been blind. This peculiar condition has been so often described that the fact is probably indisputable.

    The structural basis for such conditions probably lies in the peculiarities of the cell structure of the cortex. There is reason to believe that consciousness is affected by the activity of the cells of the stratum zonale. If these cells fail in their physiological requirements, if they are starved, or subjected to great pressure, or poisoned, consciousness is variously affected.

Functional Variations
    The possibility of being so affected by stimulation as to reply to subsequent stimuli with greater ease seems to be a function of all living cells in different degrees, and this seems to be peculiarly a function of nerve cells, of all nerve cells, probably. When cortical neurons are subjected to a series of stimulations, their metabolism becomes variously modified, so that they reply with greater ease to subsequent stimuli of the same nature. When the cells are thus stimulated by subsequent stimuli, they may cause the stimulation of the cells of the stratum zonale, and the effect in consciousness is that of a memory.

    Stimuli may, under abnormal cortical conditions, affect the cells of the deeper layers of the cortex without stimulating the cells of the stratum zonale. The person under such circumstances would not be conscious of the sensory impulses reaching the primary sense area, because of the temporary paralysis or disuse of the stratum zonale cells. But these impulses might affect the metabolism of the deeper cell layers of the cortex, and these cells, being subjected to appropriate stimulation, might bring about the stimulation of the stratum zonale cells of the overflow area, and the consciousness of memory would result.

Insular Consciousness
    When this abnormal cortical activity occurs, there may be produced a peculiar insular or lacunar form of consciousness, in which alternating areas of the cortex are subjected to this loss of function in such a way as to cause alternating personalities. Any temporary paralysis of the neuron systems by which the anterior association areas are related to other parts of the cortex would result in losing to the individual all sense of personality for a time. The activities of other cortical areas are usually partially retained, so that persons thus affected do not lose the power of speech, of using good language, of counting money, and of buying and selling with a certain ability. They retain most of their habits and faculties, though these may be subject to great variations in the different personalities. The instinctive and emotional states usually are greatly varied because of the variations in the liminal value of the different neuron systems which carry inhibitory impulses.
Multiple Personalities
    The number of personalities in which any person may dwell at different times is not known to be limited by anything except the length of the patient’s life and the time which is employed in the different states as they follow one another. Many physicians suppose that exact information concerning the occurrences of these alternating lives may be secured by hypnotism. But the extreme irritability of certain neuron groups, together with the comparative inefficiency of the inhibitions in hysterical persons, lessens the value of this method of securing information concerning such people. Statements made under hypnosis should be very carefully verified before any conclusions concerning the matter should be accepted.

    Multiple personality may be defined as the abnormal consciousness associated with the activity of the anterior association areas following some disturbance of the functions of the neuron systems relating this area to other parts of the cortex.

Recognition of Truths
    It has been noticed that of all things recognized as true, there are some things which seem to have a greater truth, or a higher truth, or a finer truth, as it is variously termed. The facts of the newer scientific attainments do not impress us as being quite so beautifully true as do the facts of older truths. No description of a colony of bacteria could now inspire a poem, though that culture might be the result of greater real bravery than any heroism of ancient times. For example, in the study of yellow fever, lives were risked and lives were lost in order that facts might be determined concerning the deadly scourge. Facts were determined, and for every life lost thousands have already been saved, while the future is full of life which would have been sacrificed to the fever under ignorance. In all of history is found no braver deed than this, yet where is the poet who sings of such courage? It is said that “time makes ancient good uncouth,” but it is time that makes ancient good a thing of poetry and beauty. New facts are not in themselves inspiring; new attainments need mellowing until they are sweet with many days of sunshine.
Consciousness of Beauty
    Cortical association processes which follow a series of neuron groups whose liminal value has been lowered during racial development are those processes which are concerned in the consciousness of the recognition of truths. A certain pleasure is associated with the recurrence of activity of cortical neurons, and this sense of pleasure gives the sensation of the beauty of the older truths, the poetry of deeds long since performed bravely, and the consciousness of being uplifted, and inspired, and encouraged, which results from the appreciation of the truth long known, and thus called “everlasting.”

    Truths newly discovered, which are not related to the so-called “higher” truths, do not arouse such feelings. This is partly due to the lack of the associations which are brought into play with the recurrence in consciousness of ideas before experienced, but it is also due in part to the fact that the newer facts have not any series of neuron groups ready for their reception. The science of today begins the preparation for the “higher” truths of tomorrow. The foundation for all grandeur and nobility of thought must be laid in the solid and undecorated facts; but when the facts have been subjected to the association processes, when complex relationships are established between the neurons in which are laid down the memories of the facts, the appreciation of their significance, and the coordination of the motor reactions which give efficient reply to the environmental variations upon which all this nervous activity is based, then comes the time when the seeds of truth in the mere facts blossom into the beauty of feeling and expression: the fruit that they bear is achievement and progress.