Biology and Neurophysiology of the Conditioned Reflex and Its Role in Adaptive Behavior: International Series of Monographs in Cerebrovisceral and Behavioral Physiology and Conditioned Reflexes, Volume 3

By Peter K. Anokhin

International Series of Monographs in Cerebrovisceral and Behavioral Physiology and Conditioned Reflexes, Volume 3: Biology and Neurophysiology of the Conditioned Reflex and its Role in Adaptive Behavior focuses on the biological roots, characteristics, and nature of conditioned reflex and its function in adaptive behavior. The monograph first discusses the biological roots of the conditioned reflex. Concerns include sequential order of external influences and living protoplasm; anticipatory processes of protoplasm and the conditioned reflex; adaptive features of the conditioned reflex; and inborn signalization in higher animals. The book then takes a look at the nature of the unconditioned reflex, including biological nature of reinforcement; value of the temporal relationships of conditioned and unconditioned reflexes; and fixation of sequential order without the factor of reinforcement. The text describes systemogenesis as an evolutionary basis for the development of unconditioned reflexes; concepts concerning the nature of the coupling process; and hypothesis of the convergent coupling of the conditioned reflex. The book also examines functional system as a basis of the physiological architecture of behavioral acts. The monograph is a dependable source of data for readers interested in conditioned reflex and its function in adaptive behavior.

• Language: English
• Publisher: Elsevier Science
• Release date: Oct 22, 2013
• ISBN: 9781483145518

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Angeles

CHAPTER 1

The Biological Roots of the Conditioned Reflex

Publisher Summary

This chapter focuses on the adaptive features of the conditioned reflex. The inborn or unconditioned reflexes are not developed in a given individual life but are presented. Acquiredness is an essential feature of the conditioned reflex because it characterizes the principal peculiarity in the adaptive behavior of the animal. The second essential characteristic of the conditioned reflex is the changeability or lability of the acquired neural connection. It is gradually lost as soon as it becomes inappropriate for the newly established conditions, that is, when the main reinforcing factor in the form of an unconditioned reflex disappears. The third characteristic of the conditioned reflex is its signaling character. The primary neural substance and the central nervous system could be regarded as substrates of high chemical and structural specialization. The chapter further discusses the anticipatory processes of protoplasm and the conditioned reflex and explores signalization in higher animals.

STATEMENT OF THE PROBLEM

In most investigations the conditioned reflex is thought to be something definite. It is from this definitive concept of the conditioned reflex that many authors begin their analysis of its mechanisms and adaptive role in the life of animals and man. On the other hand, ontogenetic and phylogenetic investigations of conditioned reflexes are few. Finally, there is an absence of investigation into the biological roots of the conditioned reflex, i.e., the first appearance during evolution of those adaptive characteristics inherent in the conditioned reflex in its most pronounced form in lower and higher animals.

In the course of hundreds of millions of years, primordial life developed together with the evolution of the basic inorganic properties of the earth. At present there is no doubt that primordial living matter was able to assert its right to exist during its development only by adapting itself to external factors and developing reactions of a survival nature.

A number of questions immediately arise. To what external factors did primordial living forms need to adapt in the early stages of our planet’s development? With the help of what mechanisms and processes were the earliest forms of life able to overcome harmful influences and thus survive? And did not these adaptive characteristics which acquired such a decisive significance in the conditioned reflex originate here during the first stages of life ?

In order to answer these questions it is evident that we must, as thoroughly as possible, characterize the conditioned reflex as a specific form of the adaptive reactions of the organism. We must identify those parameters which are most specific for the conditioned reflex. The identification of each parameter, in its turn, will help to determine its origin and form in the depth of ages. In other words, we may be able to discern to what living organism the adaptive element became useful for the first time.

Consequently, we need not consider by means of what substrate this parameter of adaptation is implemented and what kind of complex mechanisms of the organism ensure this form of adaptation.

Neither shall we use the level of somatic organization of a given species of animals as a decisive criterion. The decisive question must be the form of adaptation and its close connection with a specific feature of the inorganic world. For example, gravity as a fundamental physical factor, existing before the appearance of life on earth, necessitated adaptation to itself in all animals regardless of their organization and zoological classification. Thus weight, as the primary parameter of the external world, is essential for the fullest development of the capacity for adaptation of all organisms. Is there a similar parameter in the case of the development of conditioned reflex reactions? Do the adaptive characteristics reflect some kind of specific factor of the external world ?

We can answer these questions only after an analysis of all those adaptive characteristics of the conditioned reflex which make it possible to separate it into an independent group of the organism’s reactions.

ADAPTIVE FEATURES OF THE CONDITIONED REFLEX

In order to solve the problem of the primary characteristic of the conditioned reflex as a specific adaptive act, those characteristics which were formulated by Pavlov must be analyzed first.

Wishing to characterize this new physiological reaction, he first turned his attention to the fact that it is elaborated de novo, that it had not previously existed in the functional organization of the animal’s brain. He also observed that this reaction appears only with a special combination of conditions which are essential for the development of the reaction, and which he therefore called conditioned.

According to this characteristic of being developed or acquired during the life of an animal, a distinction was made between the conditioned reflex and another form of adaptive reaction, inborn activity, accordingly called the unconditioned reflex.

We can, therefore, logically state that the criterion for separating the conditioned reflex into a special category is the fact that it is acquired rather than inborn. It follows that the introduction of the criterion of acquiredness is based on the premise that inborn or unconditioned reflexes are not developed in a given individual life but are presented, so to speak, in a final form. Acquiredness, then, is an essential feature of the conditioned reflex, for it characterizes the principal peculiarity in the adaptive behavior of the animal.

We saw that the concept of acquiredness inevitably assumes that the other form of behavior, the unconditioned reflex, is not acquired. We shall see later, however, that acquiredness must have two meanings. One of them must refer to the acquisition of conditioned connections in the individual life of the animal, while the other refers to those reactions which regularly appear on a basis of those neural structures acquired during phylogenesis, reflecting the corresponding ecological factors of a given species of animal. Otherwise, the appearance of complex behavioral acts or even systems of these acts in newborn animals could not be explained on a strictly scientific and deterministic basis. At the same time an impassable abyss would exist between inborn and acquired behavioral acts.

The second essential characteristic of the conditioned reflex is the changeability or lability of the acquired neural connection. It is gradually lost as soon as it becomes inappropriate for the newly established conditions, i.e., when the main reinforcing factor in the form of an unconditioned reflex disappears.

It must, however, be noted that this characteristic of the conditioned reflex is not as peculiar as acquirability, inasmuch as the unconditioned reflexes also have a sufficient degree of lability. Thus, the unconditioned alimentary reflex disappears as soon as the alimentary excitability is decreased as a result of feeding. This decreased excitability by no means occurs because the starved blood, as the primary exciting agent of the alimentary center, has changed its composition. We know from everyday experience that for such satiety a definite sum of afferent impulses from the lingual, esophageal, and gastric receptors is quite sufficient. We must recognize the presence of wide lability also in the unconditioned reflex, although quantitatively it is not of the same order of magnitude as in the conditioned reflex. In other words, lability is a relative rather than an absolute characteristic of the conditioned reflex.

The third characteristic of the conditioned reflex is its signaling character. It develops as an anticipatory activity in Pavlov’s words, i.e., an activity which anticipates the course of sequentially developing external events.

Indeed, saliva secreted in response to a bell used as a conditioned stimulus appears not in order to digest the bell. Rather, it prepares, in anticipation, conditions for the digestion of bread which will appear only in the future. On the basis of this characteristic and dynamic feature, Pavlov formulated the principle of signalization as the basic principle regulating the adaptive significance of the conditioned reflex.

If one compares the two most characteristic features of the conditioned reflex, acquirability and signalability, then it is easy to see that in the adaptive sense the first feature is entirely subject to the second. Indeed, any kind of nervous activity in general is not individually acquired; what is acquired is the mechanism which permits the anticipation of the course of future events for the purpose of achieving the best adaptation to the environment.

It follows that signalability is the most characteristic and the most adaptive feature of the conditioned reflex. But what, in essence, is this signalization? We know that to signal means to warn about something impending. It is in this sense that Pavlov formulated the principle of signalization.

Since, however, the signal may refer only to a sequential development of external phenomena, we must emphasize its principal relation to the temporal aspects of those phenomena. The parameter of time is the external factor on the basis of which and in connection with which conditioned reflex activity could historically originate. This poses a new problem in physiology : to discover and characterize all the variations of temporal relationships which are an inseparable feature of the inorganic world that preceded the origin of life in the history of our planet.

THE TEMPORAL STRUCTURE OF THE WORLD

At the various stages of the development of science, ideas about space and time were based on different material foundations, depending primarily on advances in the field of physics. For example, several decades ago when the basic ideas of physics rested on the interaction of solid bodies, concepts were created about space and time in direct relation to the properties of solid bodies, with all the resulting limitations and deficiencies.

With the progress in the field of physics regarding the electromagnetic basis of all forms of material bodies, there developed the concept of an electromagnetic matrix which links all forms of movement and states of the material world. In particular, the theory of relativity could arise only with the development of ideas concerning the universality of these electrical processes which fill the universe. It was therefore possible to formulate new types of connections between all material phenomena of the universe (Einstein).

From the point of view developed in this book it is important to state that space and time, taken as separate entities, do not represent as absolute a law of the universe as does the space-time complex.

However, for the evaluation of the component factors of the space-time complex, it is very important to realize that rarely do both factors play a role at a given moment and to the same degree. We often encounter the fact that some individual parameter at a given moment may acquire primary significance. In this sense we must distinguish between two completely different levels of evaluation of space and time—the general philosophical, gnosiological, and the correlative, i.e., space and time as factors of adaptation of living organisms.

Indeed, since space and time as absolute factors of the material world existed during all times of transformation of the universe, then, on the scale of our planet, they naturally were the primary structure of the material world and possessed their absolute properties long before the appearance and development of living matter. From this it follows that even the primordial living forms were necessarily inscribed in these basic laws of space-time relationships; therefore, these laws became absolute factors of the adaptation of living matter to the environment. The space-time relationships had to become the inevitable foundation on which primordial life acquired its basic properties, and living organisms acquired their adaptive qualities up to the highest stage of evolution—man.

This concept can hardly be challenged by anyone : the very fact of the primacy of these laws determines their organizing role in the development of living organisms at the various stages of evolution. This cardinal fact of evolution basically changes our attitude toward the theory of space-time relationships. We cannot remain only on the level of the philosophical evaluation of the parameters of time, but we need to evaluate the whole diversity of the time structure of the world from the point of view of its significance for the progressive evolution of living matter.

Here we encounter properties of time which were never before taken into account. This is understandable. With the origin of life on earth, matter was enriched by an essentially new factor, the active relationship of living matter to all possible transformations of the space-time structure of the inorganic world, and consequently, to a living organism, time has acquired its own specific significance.

It was necessary to answer the question : in what manner could time, as a universal factor of the world, influence the development of living matter? How did organisms adapt themselves to the time factors of the movement of matter, and precisely which parameters of time proved to be the most decisive for life, ensuring its survival and progressive evolution ?

Unfortunately, there has been comparatively little analysis of this central point of evolution in biological literature. Time as a factor in the evolution of living organisms on earth and as the most important parameter in the development of their nervous activity, has hardly been subjected to serious analysis.

What is most important for us in the time relationships of animate and inanimate nature ?

The first essential point is that the basic forms of movement of matter within the space-time framework existed also in inorganic nature long before the appearance of the first living organisms. This is, of course, an important factor which makes it evident that living matter, inscribed in the already existing space-time system of the world, could not fail to reflect the characteristics of the system, its architecture, provided that these characteristics had a relation to the basic characteristic of living matter itself, i.e., survivability.

From the moment that life appeared, the relations to the individual parameters of the space-time structure drastically changed on the part of inorganic matter. The mountain, for example, as a form of inorganic matter, does not react selectively to climatic and meteorological factors which act upon it. For the mountain the problems of adaptation and survival do not exist. For living organisms the whole external inorganic world with all its diverse influences was weighed only on the scales of progressive evolution.

There appeared an active relation to the external inorganic factors and the inevitably resultant division of all factors into two major categories : those harmful to life and those contributing to its preservation. From this time on, all the diverse forms of the movement of matter within the framework of the temporal structure of the world began to be arranged by primitive living organisms according to this reciprocal scheme, and living matter began to reflect and strengthen these universal laws in its structure.

It follows that we must first of all determine what concrete temporal parameters of the movement of matter were encountered by primordial life. We must give a precise evaluation of the temporal structure of the world, i.e., of those varieties of the space-time movements of matter which may become factors forming the adaptive reactions of living matter. This makes it necessary to identify those special features of the temporal structure of the material world which were a kind of absolute imperative for the development of life on earth.

Here we see that in any attempt to concretize the space-time structure of the material world, we inevitably encounter a sequential transference of bodies in space, with sequential influences of one body on another, with a sequential development of phases of movement and transformation of matter.

In summing up these discussions, we can say from the point of view of dialectical materialism that the most essential feature of the space-time structure of the world determining the temporal relation of primitive organisms to the external inorganic world is the sequence of the influences of the outer world on these organisms, independent of the interval between these influences and of their forms of energy. In this way we identify the temporal parameter of the relationships of the organism to the inorganic world as a factor which, to a certain degree, is independent in the sense of its significance for adaptive transformations.

We now ask the question : what forms and variants of this basic time factor, the sequence of influences, does the organism encounter? In what manner does the all-encompassing movement of matter distribute itself within the framework of the absolute temporal parameter, the sequence of phenomena? In other words, what preexisting temporal structure of the inorganic world (compelling adaptation to itself) have the primary organisms encountered ?

We think that we have the possibility of identifying some temporal parameters from the basic form, the sequential arrangement, and of analyzing the significance which they could have had for the adaptive relations of primitive organisms.

The first variant is the existence of a number of such sequential phenomena, none of which is ever subsequently repeated in the course of the entire life of the organism. Symbolically, this series could be depicted as : a, b, c, …

It stands to reason, of course, that the factors of the inorganic world, a, b, c, etc., must be connected by cause-effect relations and develop in sequential order; there is also no doubt that all or some of them can exert sequential influences on the organism. However, according to stipulation, not one of these influences may ever have a repeated effect on the organism. Concretely, this can be a solar eclipse, a storm or tornado of unusual force, the passing of a comet close to the earth, etc. Surely, however, the unrepeated influences can also include those situated closer to the organism.

Some of these unrepeated influences of the environment could, of course, have some essential significance for the organism, either harmful or beneficial. The primitive organism could either resist this sudden action by means of possibilities already available in it, or be destroyed. However, these influences were always sudden and new for it.

There is possible, though, another time structure in the sequential order of external influences on the organism : certain individual factors of the environment can return and repeat their effect at definite intervals of time and consequently can be called a repeating series of sequential influences. Symbolically this second possibility can be depicted thus : abcd, abcd, abcd, …, abcd.

This scheme shows that in the inorganic world we can have this sequence of events which recur rhythmically in the same composition and in the same sequence of components. This may be, for example : day, evening, morning, or summer, fall, winter, spring, or cloud, lightning, thunder.

These series of sequentially developing and rhythmically or aperiodically recurring phenomena of the inorganic world have an absolute direction and are connected with astronomical, meteorological, and physical laws, although the duration of the rhythms in each case may differ. Consequently, the recurrence of these cycles may have a different significance for organisms with different life spans.

Until now we have taken as examples those series of sequentially developing events which have properties of absolute stability. Also conceivable, however, are sequential phenomena which, having the same parameter of recurrence or returning, at the same time have the property of relative stability. For example, a tree growing on the bank of a river and being of a certain age, can be a dwelling place for various kinds of animals only for a certain period of time, after which it may be replaced by other trees, the same or different. And yet, in the course of its life span, this tree will represent for its inhabitants a series of sequential, rhythmically recurring phenomena taking place at various times of the year, especially in northern latitudes.

Thus, both in the first case and in the second, we have one main temporal feature of sequentially developing events : a recurrence which can be either absolutely stable or relatively stable.

Of course, the property of recurrence per se of phenomena of the inorganic and later of the organic world, as a special parameter of absolute space-time sequential order, can have infinite variations in the duration of the rhythms themselves, in their stability, in the composition and length of the individual components, in their spatial localization, etc. In all these variants, however, the parameter of recurrence will be the most characteristic and specific.

TIME AND PRIMORDIAL LIFE

Thus far we have examined the sequential order of phenomena of the inorganic and partly the organic world with only one aim : to distinguish the various temporal parameters of the inorganic world which must inevitably have influenced organic matter even at its very inception. However, these temporal parameters (nonrecurrence, recurrence, duration, stability, variability, etc.) were set forth by us irrespective of another important quality which these parameters began to acquire upon interaction with living nature : their degree of importance for the support and preservation of the life process.

Undoubtedly even at the very first stages of the organization of living matter, perhaps at the stage of primary coacervates, the changes of external material conditions were classified by these rudiments of living substance as harmful or useful according to the criterion of their importance for the stabilization of polymolecular systems. This type of relationship of primary forms of living matter to external influences is particularly well described by Oparin (1953, 1957).

In spite of the relative constancy of the inorganic conditions under which life was generated (probably in primordial oceans), there was a successive change in the external influences on particles of primary living matter which could produce some kind of primitive natural selection of the most stable formations existing as open polymolecular systems (changes in temperature, reacting substances, chemical environment, currents, tides, etc.). This successive change of external influences gained particular significance at the moment when primary living organisms acquired the ability to multiply and disperse through various aqueous media with various ecological components.

A still greater number of variations of recurrence arose at the moment when the primary organisms acquired the ability to move actively. Then any recurrent movement near an immobile inorganic object, from a broad physiological point of view, led to recurring, more or less uniform influences from this immobile object on the organism. This type of repeated influence of the external world was of exceptional significance in the life of man as his potential for active movement developed.

At this point we wish to emphasize that in this period of the development of life the temporal structure of the inorganic world surrounding the organism remained the same and included at least four basic forms :

1. Action on the organism of relatively constant factors of the external milieu.

2. Action of sequential series of external influences recurring rhythmically or aperiodically.

3. Rhythmic or aperiodic influences of relatively constant and immobile external factors during active movement of living organisms.

4. Action of sequential series of never recurring factors.

All these external influences played a role in the preservation of life. Although these influences were only harmful, useful, and neutral nonrecurring episodes for living matter, in themselves they naturally were always links of continuous and sequentially developing phenomena in the general course of evolution of the space-time structure of the material world. They encountered the vital cycle of organisms, so to speak, at a tangent.

From this it follows that these never recurring influences could not exert any decisive influence on the evolution of the higher forms of adaptation of living matter to surrounding conditions and, consequently, could not become factors of organization of the protoplasmic structure of living organisms.

Let us imagine that the temporal structure of the inorganic world is represented only by this latter form of movement of matter, i.e., by series of sequential and never recurring phenomena.

Under these conditions could life, with its stabilized structures which always have an adaptive significance, develop on earth ?

No, it could not. The living organism could not have a stable and firm structure, because the latter can appear only as a result of the reflection of rhythmically and aperiodically recurring influences of the inorganic world. And even the very concept of adaptation would lose all sense in such a world of ever new influences never before experienced by the organism.

It is quite obvious that in the general course of events of the space-time structure of the world, only rhythmically and aperiodically recurring phenomena could become the temporal basis for the development of adaptive reactions of primary organisms.

Thus we have reached a definite conclusion in regard to the evolution of organisms depending on constant properties of the temporal structure of the inorganic world. This conclusion can be formulated in the following manner : the basis for the development of life and its relation to the external inorganic world was represented by the recurring influences of this external world on the organism. Precisely these influences, as a result of the initial properties of the space-time structure of the inorganic world, determined the whole anatomic organization and the adaptive functions of primordial organisms. In this respect the organization of organisms represents in the true sense of the word the reflection of the space-time parameters of their concrete environment.

It is natural that the relative constancy of the space-time relationships of the organism with the external world can be considered as a variation of the recurring influence on the organism. It all depends on what concrete temporal relationships exist between the length of the life cycle of the organism and the duration of the external influence.

One may consider as a relatively constant influence one which encompasses in its duration millions of life cycles, such as the presence of oxygen in the atmosphere; an influence may be considered relatively less constant when it encompasses only thousands of life cycles, such as the natural features of a given locality; still less constant would be the influence, for example, of some land reclamation or water diversion which in its duration may overlap only hundreds of life cycles.

Furthermore, even for primordial organisms, the rhythmic and aperiodic influences of the external world could have been of the same two kinds as those also required for higher animals. Some of them are rhythmic influences of external conditions on a sessile organism. Others, also rhythmic and aperiodic, depend upon recurring movements of the organisms itself. However, in both cases there is an essentially identical final process, a recurring influence of external factors on the organism.

SEQUENTIAL ORDER OF EXTERNAL INFLUENCES AND LIVING PROTOPLASM

From the analysis presented above, we may conclude that exactly this type of temporal relationship, recurring sequential influences, represents the universal relation of previously formed and individualized living organisms to their environment. This conclusion prompts us to discern the concrete mechanisms enabling the organism to adapt to these vitally important recurring influences. In what intimate processes of living protoplasm are these recurring influences of the external inorganic world reflected on already formed living organisms ?

To answer this question we can utilize the generally accepted concept of modern biology and biochemistry that the simplest organisms of our planet represent open systems which were connected with the environment through a series of chemical transformations beginning at the boundary of living polymolecular protoplasm and continuing in the form of a whole chain of separate reactions, ending in a result either harmful or useful for life (Oparin, 1953, 1957).

Thus, we have reason to assume that, due to the special properties of protoplasm, each of the sequentially developing external phenomena is reflected in the protoplasm of the organism itself in the form of more or less long chains of chemical transformations. Such chains of reactions may have a metabolic character supporting the life of the organism and its reproduction, but there can also arise a chain of transformations which may prove harmful to this metabolism and consequently not support the life process. However, in spite of these two biologically opposite results, both of these influences by their very nature must evoke a series of sequential and regular chemical transformations. Coming to the fore here is the basic parameter of the space-time structure of the inorganic world which always plays a dominant role in the development of living matter, the recurrence of phenomena and influences.

One may speculate about the real consequences of these influences on the primordial organism, influences which had essential significance for its survival and recurred or were constant in the course of millions of years. It is generally accepted by biochemists that any external influence on primordial organisms inevitably served as a starting point for the formation of whole chains of chemical processes and interactions, leading either to the destruction of the organism or, on the contrary, to an increase in its metabolic stability.

At the same time, however, the same sequential series of influences recurring many times inevitably led to a facilitated and accelerated catalytic type of development of these chain processes. Thus, the dominant lines of chemical chain reactions were finally created.

It is difficult to imagine that there could be ways of creating primary metabolic chains other than through the recurring influences of the external inorganic world on the organism. The recurrence of sequentially developing external influences essential to the organism was capable of creating an uninterrupted, successive, and to some degree stable chain of chemical reactions in the protoplasm.

On this basis in the evolution of life one very significant event occurred which in the course of many millions of years determined the chief features of the adaptive reactions of the organism. This event follows from the basic properties of the first living organisms as open formations with a polymolecular composition of the protoplasm. I have in mind their ability to react to changes in the surrounding world by more or less extensive chemical rearrangements, provided these changes establish a physicochemical contact with these formations.

It is natural, therefore, that if in the environment several specific events develop sequentially (for example, the seasonal rhythms, changes of temperature, currents in the oceans), then the organism must reflect each one of them in specific chemical rearrangements of its protoplasm, provided they reach a certain threshold of action. These specific chemical rearrangements can be related to the physical properties of each inorganic factor from among the long sequential series of such factors.

It is interesting that Oparin, in characterizing these relationships of primordial living matter with surrounding inorganic nature, also believes that the sequential order and speed of the reactions of the protoplasm are the decisive factors in the material organization of the first living organisms (Oparin, 1953, 1957).

Familiarity with the theories of the origin of life on earth shows that from the broad biological point of view as well as from the point of view of the above analysis of the role of the space-time structure of the world, movement of matter according to sequential, rhythmically recurring phases is a universal law determining the basic organization of living organisms on our planet (Oparin, ed., 1959).

The appearance of primordial protein bodies which later acquired an enzymatic function radically changed the whole process of the perfection of life. There arose the possibility for the development of dominant chains of reactions (i.e., with selective catalytic acceleration) and, of course, first of all the development of those reactions which, being essential for the preservation of life, recurred innumerable times under external influences. These influences could vary greatly; an example would be the periodic changes in the supply of substances necessary for the open systems of primordial organisms. However, it remains certain that the specific catalysis itself created the possibilities of the principal conditions for the development of these particular kinds of reactions.

This acceleration of reactions, as an analysis of some widely prevalent enzymatic complexes shows, can attain magnitudes of hundreds of millions, even billions, of times. In any case, at the first stages of the development of life this principle of maximum rate made it possible to form, on a background of more or less homogeneous coacervate formations, paths of the principal chains of reactions which develop at a tremendous rate. Conditions were created, therefore, for the specific and appropriate responses of living organisms to definite external stimuli.

At this focal point in the development of organisms, one remarkable gain was made which later exerted a decisive influence on the whole development of the living world.

ANTICIPATORY REFLECTION OF EVENTS OF THE EXTERNAL WORLD IN LIVING PROTOPLASM

Between sequential influences of the external world and the reactions to these influences on the part of living matter, there existed one principal difference regarding temporal parameters. External influences on the organism could occur at the most diverse time intervals and originate from the most diverse sources; only the principle of sequential order unified them. At the same time all these influences converged on the same protoplasm of living matter and evoked qualitatively different chemical reactions performed within the limits of the same protoplasmic formation.

In this way all the conditions were created for the formation of one of the decisive processes of living matter which determined the further development of the animal world and the form of its adaptation to the external world.

Indeed, if diverse chemical reactions become possible (particularly at a very high rate) in a small lump of living matter constituting a polymolecular open system, then some external influences recurring in sequential order, even separated by great intervals, became capable of uniting and being reflected in the rapid chemical transformations of this substance in accordance with the physical or chemical qualities of these influences.

Gradually, relationships were formed in which the difference in temporal parameters was increasingly apparent for events occurring in the external inorganic world and for their reflection in the chemical rearrangements of living matter. For example, external factors could influence the organism in a continuous sequential order in a circadian rhythm (degree of insolation, tides, etc.). Consequently, various kinds of chemical reactions in organisms corresponding to each of these influences also developed in a circadian rhythm. The fact, however, that these individual chemical reactions developed in a sequential order in a small but very complex polymolecular formation, led to the closest interactions of these reactions and to the formation of continuous and interdependent chains of reactive changes.

Consequently, the same properties of primordial living formations—polymolecularity, catalytic acceleration of reactions, and possibilities for the reflection of external influences—ensured both the progressive development of organisms and the reflection in them, in the chemical rearrangements of their protoplasm, of the sequentially recurring influences of the external world.

As a result of these real interactions, at this stage there was formed one universal law in the adaptation of the organism to external conditions, which later developed rapidly in the course of the entire evolution of the animal world, i.e., an extremely rapid reflection (in chemical chain reactions) of the slowly developing events of the external world.

To further elucidate this process I shall attempt to illustrate this law schematically. Let us assume that in the external world there develops a sequential series of certain phenomena which we designate as A, B, C, D. Let these phenomena act on the organism for considerable periods of time, for example, for 12 hours. Each of these phenomena evokes in the protoplasm of the organism a sequential series of chemical transformations which we will designate correspondingly by the symbols a, b, c, d. Let us assume that the series of external influences on the organism A, B, C, D (Fig. 1.1) systematically recurs for a period of many years and has an essential positive significance for its metabolic processes, establishing more perfect chains of chemical reactions, i.e., promoting the stabilization of the life process. Then, as a result of prolonged and repeated reproduction in the protoplasm of the living matter of this specific series of chemical reactions, an organic connection is established between the individual links which converts the whole series of transformations a→b→c→d into a continuous and rapidly developing chain of chemical reactions (Fig. 1.1a).

FIG. 1.1 Transformation of the slow sequence of phenomena in the environment (A, B, C, D, E) into rapidly proceeding protoplasmic processes of the living organism (a, b, c, d, e).

(a) Action of consecutively unfolding events of the environment on the organism during the first times that the organism encounters these events. Circles at the corresponding points of the organism show that every phenomenon of the environment evokes protoplasmic changes corresponding to it (A→a; B→b; C→c; D→d; E→e).

(b) The same sequence of environmental phenomena after numerous repetitions. It can be seen that the protoplasmic processes in the organism (a, b, c, d, e), which before were developing separately, have established among themselves a very close chemical connection which is achieved with much greater speed than the, actual phenomena of the environment. By means of these relationships, even the first link in a chain of environmental phenomena (A) may start the entire cycle of chemical interactions from a to e. This constitutes the basic law of the accelerated and anticipatory reflection of environmental phenomena in the protoplasm of primordial living beings. It is the prototype of the temporary connection and the conditioned reflex in higher animals.

As the data of biochemists of primordial life indicate, of decisive significance in the formation of these chains of reactions was the formation of specific catalysts which determine the main course of the chemical chain reactions in a given direction.

All these conditions, created at the very earliest stages of the evolution of living matter, led to the ability of protoplasm to acquire the potentiality to reflect in the micro-intervals of time of its chemical reactions those sequential events of the external world which by their nature can develop only in macro-intervals of time.

Gradually, then, primary organisms developed the ability to reflect the external inorganic world not passively, but actively, with an anticipation in its protoplasm of sequentially and recurrently developing phenomena of the external world.

In the protoplasm of the living organism there had been established a continuous chain of chemical reactions which formerly was evoked by the sequential action of external factors A, B, C, D, which may have been separated by considerable intervals of time. Now the action of the first factor A alone is capable of initiating and bringing into an active state the whole sequential chain of chemical reactions.

Historically, in living protoplasm, conditions inevitably had to be created under which the rate of the chemical reactions of the protoplasm ensured the organism’s anticipation of the development of sequential, frequently recurring external influences (see Fig. 1.1b).

Thus, from our point of view, at a very early stage evolution discovered this universal and only possible way for the organism to adapt to the external world. The deep significance of this new property of the primordial organism lies primarily in the universality and rapidity of the chemical reactions of its protoplasm in response to the slowly developing influences of the environment.

First, all the originally separate chemical reactions of the protoplasm occurring in response to external influences are chemically united into a single chain and form, as a result of numerous repetitions, a path developing chemical reactions proceeding at high speed (a→b→c→d→e).

This is the new feature acquired by the primordial organism during the formation of a polymolecular substance, i.e., protoplasm. However, the events of the outside world (A→B→C→D→E) are occurring as slowly as before.

What happens now, after the chemical interactions of the protoplasm have changed ?

Now the chemical reactions of the protoplasm a→b→c→d→e constitute a single entity. All that is needed, therefore, is to evoke the process a, which corresponds to the first component A in the series of events of the external world, and the entire chain with its very high rates of microchemical reactions explodes, with the process of excitation almost instantaneously passing through the entire course of the interactions from a to e. This was the cause for the high reaction rates and, consequently, for the anticipation of the course of a sequential series of external events (A→B→C→D→E) in the chemical processes.

It must be emphasized that this molecular chemical process was developing at the dawn of life on the level of the protoplasm of a unit, perhaps even of microscopic size.

Due to this marvelous property of living protoplasm, its chemical process, e.g. d, develops long before the external factor D, which had been evoking it in the past, sets in.

Living matter gained great advantages from this form of reaction to recurring series of sequential influences. As a matter of fact, without this anticipatory development of chains of chemical reactions it is difficult to imagine even such a simple act as, for example, the swallowing and digestion of a small piece of food by the amoeba or the seizing and digesting of bacteria by the bacteriophage.

The whole history of the development of the animal world clearly demonstrates the perfection of this universal and most ancient law, which could be called an anticipatory reflection of reality, i.e., an enormously accelerated development of chains of chemical reactions which in the past reflected sequential and slow transformations of this reality.

Returning to the initial premise of this problem, we could say that the anticipatory reflection of reality is the basic form of adaptation of living matter to the space-time structure of the inorganic world, in which sequential order and recurrence are the basic temporal parameters.

Up to this point no qualitative distinction has been made between the sequentially occurring events of the external world. They simply followed each other in a definite order. However, in the real life of an organism this is never the case. Every sequence is always interrupted by some essential event, vitally important to the organism. Actually, any sequence of events in the life of an organism consists of vitally important events interspersed with indifferent influences.

Let us assume that in our example (see Fig. 1.1), the events A, B, C of the external world are indifferent for the animal; for example, A refers to the opening of the door into the room where the dog is, B to the entrance of a man with a dish, and C to the movement of the man toward the dog. D, however, is the intake of the food from the dish by the dog.

If this sequence is repeated many times, then in the protoplasm of the nerve cells of the brain an intimate chemical connection is established not merely on the basis of the sequence alone, but also due to the reinforcing action of the vitally important stimulus, i.e., the reverse chemical influence of the reinforcement on the preceding processes from the preceding events (the stimuli). In our example these are A, B, C.

It follows that with such a sequence of factors (a recurring sequence), the chemical process evoked by factor A (or by any earlier factor) is not retained in the structures a alone, but spreads immediately all the way to the chemical complex d. As is evident, in this case the chemical process d, which corresponds to the phenomenon D of the external world, will develop in the cells of the brain or in the protoplasm of a primordial organism sooner than the actual phenomenon D sets in.

This is the chemical process of the protoplasm (or the excitation) which anticipates the course of the external events that occur considerably more slowly. Thus, the living protoplasm has become a unique accelerator of the course of external events.

From this anticipation, however, it follows that in the series of sequentially occurring events of the external world, the factor A, which evokes a chain of processes including the process d, becomes a signal for the approaching, but as yet not present factor D. In this case the actual chemical process d constitutes an anticipatory reaction with respect to factor D.

Consequently, the very fact of the appearance of signalization and temporary connections can be accepted as one of the most ancient laws in the development of living matter. In this sense one must understand Pavlov’s expression that temporary connections constitute a universal phenomenon of nature.

Accompanying the origin and perfection of living matter and being a natural result of the space-time structure of the world, this law was fixed by natural selection and was further established in the stabilized structures of protoplasm. Consequently, the principle of anticipation of impending external events in the protoplasmic processes of the organism can be considered as the basis for the creation and fixing of all those structures of the organism which purposefully adapt it to the external world on the basis of signalization and temporary connections.

It is, therefore, hardly surprising that this particular function of the organism, providing the greatest potentialities for adaptation and progress, soon began to specialize in a particular substrate whose main function became the rapid chemical coupling of all simultaneously and sequentially developing chemical reactions. The nervous system became such a substrate.

From this broad point of view the primary neural substance, and subsequently also the central nervous system, can be regarded as a substrate of high chemical and structural specialization which developed the capacity for the maximum and fastest anticipation of sequential and recurring phenomena of the external world (Anokhin, 1956d).

ANTICIPATORY PROCESSES OF PROTOPLASM AND THE CONDITIONED REFLEX

In one of our previous publications we showed that the attendant approaching the dog with food from the first floor to the third constitutes a definite sequence of stimuli (Anokhin, 1962a). This approach of the attendant demands considerable time because it occurs within the physico-mechanical limitations of space.

We have quite different relationships in the neural substrate of the animal’s brain. The processes in the receptors and in the neural substance occur in milliseconds. Consequently, as early as the action of the first agent of this whole series of external events (the sound of the door on the lower floor) the brain can immediately reproduce the entire chain of chemical reactions previously fixed by these slowly proceeding events of reality, provided the same sequence of these events has recurred many times.

In this fact one cannot fail to see the vast achievements of evolution which proved to be capable, on the basis of primary protoplasmic chains of chemical reactions, of creating a mechanism which permits achieving a greatly accelerated reflection of reality and anticipating the sequential course of actual phenomena of the external world.

The different rates at which phenomena occur in natural reality and in the neural substance of the brain are the prerequisites for the spread of this anticipatory excitation.

If we compare the different levels of organization of living matter discussed above, we see that in the whole course of the evolution of living matter, the principle of anticipatory reflection of the external world is an inalienable part of life and of its adaptation to surrounding conditions.

The brain, as an organ specialized in this direction, has no limits to this anticipatory reflection of reality. It has the ability to reflect in micro-intervals of time chains of events which may occupy many years.

Comparing the anticipatory reflection in primitive organisms with the highly specialized form of anticipatory reflection of the external world which is manifested in the conditioned reflex in higher animals, we by no means remove the qualitative difference between these two phenomena. We must only remember that the comparison and the classification of many phenomena inevitably demand a guiding criterion.

Therefore, naturally, we must ask : what is the most characteristic feature of the conditioned reflex, which determines its essence ? Of all its possible qualities, that of anticipation, or signalization, concerning imminent, i.e., future events of the external world, is the most distinguishing. Neither variability nor stability nor acquiredness, etc., can compare in their significance with this biological quality. Since animals have the ability to prepare in response to a signal for as yet only impending links of sequentially developing events, this major discovery by Pavlov became the central point of progressive evolution.

If, however, this basic property (parameter) of the examples discussed is the most ancient, then consequently, according to this property, we can fully consider the adaptive potential of lower and higher animals.

It is natural that the structural and quantitative complexities of the mechanisms which ensure more extensive signalizations have led to further qualitative changes in the behavior of animals. However, signalization, as a universal parameter of adaptation to the external world, has not lost its principal significance.

Consequently, the conditioned reflex of higher animals, evaluated according to the parameter of signalization, is only a particular case of highly specialized forms of the anticipatory reflection of reality, i.e., adaptation to future events (Anokhin, 1949c) (anticipatory activity according to Pavlov).

In the light of the above historical laws on the development of the biological bases of conditioned reflex activity, the complete artificiality of an entire series of questions referring to the conditioned reflex becomes evident, such as : When in evolution did the conditioned reflex appear? Do protozoa and plants have a conditioned reflex? Can an inborn activity be signaling? etc.

From this point of view, the universal principle of all forms of adaptation of an organism to the conditions of the surrounding world is the anticipatory reflection of sequentially and recurrently developing events of the external world, an anticipatory adaptation to forthcoming changes of external conditions or, in a broad sense, the formation of preparatory changes for future events in response to a signal.

As we have seen, this principle was operating even from the first stages of the formation of living matter. Therefore, the question can only concern the form and concrete mechanisms in which this principle of anticipatory reflection of the external world is present at a given level of development. In protozoa it occurs in the form of chains of chemical transformation of protoplasm which anticipate the development of a sequential series of external events. In higher animals it appears in the form of the participation of specialized neural apparatuses which give a tremendous advantage in perceiving the external world and in the rapidity of anticipation. However, in all cases this form of anticipatory reflection has one decisive feature—signalization. For animals which have a nervous system, this is the conditioned reflex.

In view of what has been said, the second question also loses its sense, namely : can a temporary connection be elaborated in protozoa and plants? Since both represent living formations with a complex molecular and cellular structure, and since they are subject to constant series of sequential and recurring influences (especially the plants), one can definitely state that natural signal changes have taken root in both protozoa and plants, or that these changes can be developed de novo. It is only necessary to observe the requirements stated above : prolonged recurrence and a sufficiently well-chosen essential factor for the life of a given plant or