Part 10

”_The specific elementary accumulators_ (previously termed specific potential elements) are thus susceptible now of receiving a third name, namely, that of _mnemonic elements_." “The preservation of memories is to be ascribed to the accumulations of substance,” while “the reawakening of these memories consists in the restitution of the same currents [by discharge of the substance] as had formerly constituted the actual sensation or impression.”

By this hypothesis Rignano explains not only memory but the inheritance of acquired characters and the whole process of specialization of cells, all of which phenomena are special instances of such elementary accumulators of organic energy being formed and discharged.

Any attempt, with our present knowledge, to postulate particular kinds of chemical or physical changes in the nervous system as the theoretical residua of physiological dispositions left by psychological experiences must necessarily be speculative. And any hypothesis can only have so much validity as may come from its capability of explaining the known facts. It is interesting, however, to note some of the directions which attempts have taken to find a solution of the problem. For the present it is best to rest content with the theory to which we have been led, step by step, in our exposition, namely, that conservation is effected by some sort of physiological residua. This theory, of course, is an old one, and has been expressed by many writers. What we want, however, is not expressions of opinion but facts supporting them. It would seem as if the facts accumulated in recent years by experimental and abnormal psychology all tended to strengthen the theory, notwithstanding an inclination in certain directions to seek a psychological interpretation of conservation.

Some minds of a certain philosophical bent will not be able to get over the difficulty of conceiving how a psychological process can be conserved by the physical residuum of a physiological process. But this is only the old difficulty involved in the problem of the relation between mind and brain of which conservation is only a special example. That a mind process and a brain process are so intimately related that either one determines the other there is no question. It is assumed in every question of psycho-physiology. The only question is the How. I may point out in passing, but without discussion, that if we adopt the doctrine of panpsychism for which I have elsewhere argued[62]—namely, that there is only one process—the mental—in one and the same individual, and that what we know as the physical process is only the mode of apprehending the mental process by another individual; if we adopt this doctrine of monism the difficulty is solved. In other words, the psychical (and consciousness) is reality, while matter (and physical process) is a _phenomenon_, the disguise, so to speak, under which the psychical appears when apprehended through the special senses. According to this view in their last analysis all physical facts are psychical in nature, although not psychological (for psychological means consciousness), so that physiological and psychical are one. To this point I shall return in another lecture.

=Neurograms.=—Whatever may be the exact nature of the theoretical alterations left in the brain by life’s experiences they have received various generic terms; more commonly “brain residua,” and “brain dispositions.” I have been in the habit of using the term _neurograms_ to characterize these brain records. Just as telegram, Marconigram, and phonogram precisely characterize the form in which the physical phenomena which correspond to our (verbally or scripturally expressed) thoughts, are recorded and conserved, so neurogram precisely characterizes my conception of the form in which a system of brain processes corresponding to thoughts and other mental experiences is recorded and conserved.[63]

Of course it must not be overlooked that such neurograms are pure theoretical conceptions, and have never been demonstrated by objective methods of physical research. They stand in exactly the same position as the atoms and molecules and ions and electrons of physics and chemistry, and the “antibodies” and “complements” of bacteriology. No one has seen any of these postulates of science. They are only inferred. All are theoretical concepts; but they are necessary concepts if the phenomena of physical, chemical, and bacteriological science are to be intelligible. The same may be said for brain changes if the phenomena of brain and mind are to be intelligible.

And so it happens that though our ideas pass out of mind, are forgotten for the moment, and become dormant, their physiological records still remain, as sort of vestigia, much as the records of our spoken thoughts are recorded on the moving wax cylinder of the phonograph. When the cylinder revolves again the thoughts once more are reproduced as auditory language. A better analogy would be the recording and reproducing of our thoughts by the dynamic magnetization of the iron wire in another type of the instrument. The vibration of the voice by means of a particular electrical mechanism leaves _dynamic traces_ in the form of corresponding magnetic changes in the passing wire, and when the magnetized wire again is passed before the reproducing diaphragm the spoken thoughts are again reproduced. So, when the ideas of any given conscious experience become dormant, the physiological records, or dynamic rearrangements, still remain organized as physiological unconscious complexes, and, with the excitation of these physiological complexes, the corresponding psychological memories awake.

It is only as such physiological complexes that ideas that have become dormant can be regarded as still existing. If our knowledge were deep enough, if by any technical method we could determine the exact character of the modifications of the dispositions of the neurons that remain as vestiges of thought and could decipher their meaning, we could theoretically read in our brains the record of our lives, as if graphically inscribed on a tablet. As Ribot has well expressed it: “... Feelings, ideas, and intellectual actions in general are not fixed and only become a portion of memory when there are corresponding residua in the nervous system—residua consisting, as we have previously demonstrated, of nervous elements, and dynamic associations among those elements. On this condition, and this only, can there be conservation and reproduction.”[64] _Dormant ideas are thus equivalent to conserved physiological complexes._ We may use either term to express the fact.

The observations and experiments I have recited have led us to the conclusion that conservation of an experience is something quite specific and distinct from the reproduction of it. They compel us to the conclusion that we are entitled, as I pointed out at the opening of these lectures, to regard memory as a _process_ and the result of at least two factors—conservation and reproduction. But as conservation is meaningless unless there is something to be conserved, we must also assume _registration_; that is, that every conserved mental experience is primarily registered somehow and somewhere. Conservation implies registration.

Such is the theory of memory as a _process of registration, conservation, and reproduction_. Thus it will be seen (according to the theory) that ideas which have passed out of mind are preserved, if at all, not as ideas, but as physical alterations or records in the brain neurons and in the functional dynamic arrangements between them.

From this you will easily understand that while, as you have seen from concrete observations, we can have conservation of experiences without memory (reproduction) we cannot have memory without conservation. Three factors are essential for memory, and memory may fail from the failure of any one of them. Unless an experience is registered in some form there will be nothing to preserve, and memory will fail because of lack of registration. If the experience has been registered, memory may fail, owing to the registration having faded out, so to speak, either with time or from some other reason; that is, nothing having been conserved, nothing can be reproduced. Finally, though an experience has been registered and conserved, memory may still fail, owing to failure of reproduction. The neurographic records must be made active once more, stimulated into an active process, in order that the original experience may be recalled, i.e., reproduced. Thus what we call conscious memory is the final result of a process involving the three factors, registration, conservation, and reproduction.

=Physiological memory.=—Memory as commonly regarded and known to psychology is a _conscious_ manifestation but, plainly, if we regard it, as we have thus far, as a process, then, logically, we are entitled to regard any process which consists of the three factors, registration, conservation, and reproduction of experiences, as memory, whether the final result be the reproduction of a conscious experience, or one to which no consciousness was ever attached. In other words, theoretically it is quite possible that acquired physiological body-experiences may be reproduced by exactly the same process as conscious experiences, and their reproduction would be entitled to be regarded as memory quite as much as if the experience were one of consciousness. In principle it is evident that it is entirely immaterial whether that which is reproduced is a conscious or an unconscious experience so long as the mechanism of the process is the same.

Now, as a matter of fact, there are a large number of acquired physiological body-actions which, though unconscious, must be regarded quite as much as manifestations of memory as is the conscious repetition of the alphabet, or any other conscious acquisition. Having been acquired they are _ipso facto_ reproductions of organized experiences. We all know very well that movements acquired volitionally, and perhaps laboriously, are, after constant repetition, reproduced with precision without conscious guidance.

They are said to be automatic; even the guiding afferent impressions do not enter the content of consciousness. The maintaining of the body in one position, sitting or standing, though requiring a complicated correlation of a large number of muscles, is carried out without conscious volition. It is the same with walking and running. Still more complicated movements are similarly performed in knitting, typewriting and playing the piano, shaving, buttoning a coat, etc. We do not even know the elementary movements involved in the action, and must become aware of them by observation. The neurons remember, i.e., conserve and reproduce the process acquired by previous conscious experiences. But though it is memory it is not conscious memory, it is unconscious memory, i.e., a physiological memory. The acquired dispositions repeat themselves—what is called habit. Precision in games of skill largely depend upon this principle. A tennis player must learn the “stroke” to play the game well. This means that the muscles must be coordinated to a delicate adjustment which, once learned, must be unconsciously remembered and used, without consciously adjusting the muscles each time the ball is hit. Indeed some organic memories are so tenacious that a player once having learned the stroke finds great difficulty even by effort of will in unlearning it and making his muscles play a different style of stroke. Likewise one who has learned to use his arms in sparring by one method finds difficulty in learning to spar by another method. In fact almost any acquired movement is compounded of elementary movements which by repetition were linked and finely adjusted to produce the resultant movement, and finally conserved as an _unconscious physiological arrangement_. As one writer has said, the neuron organization “faithfully preserves the records of processes often performed.”

In what has just been said the fact has not been overlooked that the initiation or modification of any of the movements which have been classed as physiological memory (knitting, typewriting, games of skill, etc.), even after their acquisition, is necessarily voluntary and therefore, so far, a conscious memory, but the nice coördination of afferent and efferent impulses for the adjustment of the muscles involved becomes, by repetition, an unconscious mechanism, and is performed outside the province of the will as an act of _unconscious memory_. By repeated experience the neurons become functionally organized in such a way as to acquire and conserve a functional “disposition” to reproduce the movements originally initiated by volition.

Physiological memory has indeed, as it seems, been recently experimentally demonstrated by Rothmann, who educated a dog from which the hemispheres had been removed to perform certain tricks; e. g., to jump over a hurdle.[65]

Still another variety of memory is _psycho-physiological_. This type is characterized by a combination of psychological and physiological elements and is important, as we shall see later, because of the conspicuous part which such memories play in pathological conditions. Certain bodily reactions which are purely physiological, such as vaso-motor, cardiac, respiratory, intestinal, digestive, etc., disturbances, become, as the result of certain experiences, linked with one or another psychical element (sensations, perceptions, thoughts), and, this linking becoming conserved as a “disposition,” the physiological reaction is reproduced whenever the psychical element is introduced into consciousness. Thus, for example, the perception or thought of a certain person may become, as the result of a given social episode, so linked with blushing or cardiac palpitation that whenever the former is thrust into consciousness, no matter how changed the conditions may be from those of the original episode, the physiological reaction of the blood vessels or heart is reproduced. Here the original psycho-physiological experience—the association of an idea (or psychical element) with the physiological process is conserved and reproduced. Such a reproduction is essentially a psycho-physiological memory depending wholly upon the acquired disposition of the neurons.[66]

Thus, to take an actual example from real life, a certain person during a series of years was expecting to hear bad news because of the illness of a member of the family and consequently was always startled, and her “heart always jumped into her throat,” whenever the telephone rang. Finally the news came. That anxiety is long past, but now when the telephone rings, although she is not expecting bad news and no thought of the original experience consciously arises in her mind, her “heart always gives a leap and sometimes she bursts into a perspiration.”

A beautiful illustration of this type of memory is to be found in the results of the extremely important experiments, for psychology as well as physiology, of Pawlow and his co-workers in the reflex stimulation of saliva in dogs. These experiments show the possibility of linking a physiological process to a psychological process by education, and through the conservation of the association reproducing the physiological process as an act of unconscious memory. (The experiments, of course, were undertaken for an entirely different purpose, namely, that of studying the digestive processes only.) It should be explained that it was shown that the salivary glands are selective in their reaction to stimuli in that they do not respond at all to some (pebbles, snow), but respond to others with a thin watery fluid containing mere traces of mucin or a slimy mucin-holding fluid, according as to whether the stimulating substance is one which the dog rejects, and which therefore must be washed out or diluted (sands, acids, bitter and caustic substances), or is an eatable substance and must as a food bolus be lubricated for the facilitation of its descent. Dryness of the food, too, largely determined the quantity of the saliva.

Now the experiments of the St. Petersburg laboratory brought out another fact which is of particular interest for us and which is thus described by Pawlow. “In the course of our experiments it appeared that all the phenomena of adaptation which we saw in the salivary glands under _physiological_ conditions, such, for instance, as the introduction of the stimulating substances into the buccal cavity, reappeared in exactly the same manner under the influence of _psychological_ conditions—that is to say, when we merely drew the animal’s attention to the substances in question. Thus, when we pretended to throw pebbles into the dog’s mouth, or to cast in sand, or to pour in something disagreeable, or, finally, when we offered it this or that kind of food, a secretion either immediately appeared or it did not appear, in accordance with the properties of the substance which we had previously seen to regulate the quantity and nature of the juice when _physiologically_ excited to flow. If we pretended to throw in sand a watery saliva escaped from the mucous glands; if food, a slimy saliva. And if the food was dry—for example, dry bread—a large quantity of saliva flowed out even when it excited no special interest on the part of the dog. When, on the other hand, a moist food was presented—for example, flesh—much less saliva appeared than in the previous case however eagerly the dog may have desired the food. This latter effect is particularly obvious in the case of the parotid gland.”[67]

It is obvious that in these experiments, when the experimenter pretended to throw various substances into the dog’s mouth, the action was effective in producing the flow of saliva of specific qualities because, through repeated experiences, the pictorial images (or ideas) of the substance had become associated with the specific physiological salivary reaction, and this association had been conserved as a neurogram. Consequently the neurographic residue when stimulated each time by the pretended action of the experimenter reproduced reflexly the specific physiological reaction and, so far as the process was one of registration, conservation, and reproduction, it was an act of psycho-physiological memory.

That this is the correct interpretation of the educational mechanism is made still more evident by other results that were obtained; for it was found that the effective psychical stimulus may be part of wider experiences or a complex of ideas; everything that has been in any way psychologically associated with an object which physiologically excites the saliva reflex may also produce it; the plate which customarily contains the food, the furniture upon which it stands; the person who brings it; even the sound of the voice and the sound of the steps of this person.[68]

Indeed, it was found that any sensory stimulus could be educated into one that would induce the flow of saliva, if the stimulus had been previously associated with food which normally excited the flow. “Any ocular stimulus, any desired sound, any odor that might be selected, and the stimulation of any part of the skin, either by mechanical means or by the application of heat or cold, have in our hands never failed to stimulate the salivary glands, although they were all of them at one time supposed to be inefficient for such a purpose. This was accomplished by applying these stimuli simultaneously with the action of the salivary glands, this action having been evolved by the giving of certain kinds of food or by forcing certain substances into the dog’s mouth.”[69] It is obvious that reflex excitation thus having been accomplished by the education of the nerve centers to a previously indifferent stimulus the reproduction of the process through this stimulus is, in principle, an act of physiological memory.[70]

The experiences of the dogs embraced quite large systems of ideas and sensory stimuli which included the environment of persons and their actions, the furniture, plates, and other objects; and various ocular, auditory, and other sensory stimuli applied arbitrarily to the dogs. All these experiences had been welded into an associative system and conserved as neurograms. Consequently it was only necessary to stimulate again any element in the neurogram to reproduce the whole process, including the specific salivary reaction.

We shall see later that these experiments acquire additional interest from the fact that in them is to be found the fundamental principle of what under other conditions can be recognized as a _psycho-neurosis—an abnormal or perverted association and memory_. The effects produced by this association of stimuli may be regarded as the germ of the habit psychosis, and in these experiments we have experimental demonstration of the mechanism of these psychoses—but this is another story which we will take up by and by.