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Approximate reaction. Study of the orienting reaction

ESTIMATED REACTION

reaction (reflex “What is it-”, according to I.P. Pavlov), a complex of shifts in different systems in the body of an animal or human, caused by any unexpected change in the situation and due to the special activity of the central nervous system. Changes in the activity of the central and autonomic nervous system during O. r. aimed at mobilizing analytical and propulsion systems organism, which contributes to a quick and accurate assessment of a new situation and the development of an optimal apparatus for controlling a new non-automated action. At the same time, suppression of previous activity and turning of the head (ears, eyes) towards the stimulus occur. O. r. is accompanied by an increase in the level of adrenaline in the blood, a change in the electrical potential of the skin (galvanic skin reflex), an activation reaction (in the form of desynchronization of the slow electrical activity of the cortex cerebral hemispheres brain) and a number of other phenomena that characterize the body’s preparation for action in a new situation. Functions not involved in such actions (for example, digestion) are inhibited. If a change in the situation is accompanied by unconditional irritation, that is, reinforced by it, then on the basis of O. r. a conditioned reflex can be developed; an indifferent stimulus becomes significant, significant for the organism. If a new stimulus turns out to be insignificant for the body, its repeated use leads to “addiction” and O. r. fades away.

O. r. plays an important role in the organization of higher education nervous activity animals and humans. According to modern ideas, the basis of O. r. there are activating influences on the higher parts of the central nervous system from the reticular formation. At the same time, the level of excitability of the corresponding zones of the cerebral cortex significantly increases, which creates favorable conditions for the formation of a conditioned reflex circuit in the cortex. In humans, O. r. participates in acts of varying degrees of complexity - from a reaction to any new agent to the most complex mental work, when, faced with an unexpected fact or thought, a person concentrates and mobilizes to comprehend them. The basis of the attention that arises in this case is the OR, which, according to V. M. Bekhterev, appears in the form of a “concentration reflex.” The role of O. r. V mental activity a person is more fully revealed when it is violated, for example in schizophrenia. Dropping out important property O. r. - its extinction with repetition of irritations - significantly reduces the possibility of adaptation to new conditions. In other cases, the presence of only the inhibitory component of the O. r. in the absence of it research form paralyzes the ability to analyze a new situation and respond adequately to it.

Lit.: Pavlov I.P., Complete. collection op., 2nd ed., vol. 3, book. 1-2, M. - L., 1951; Indicative reflex and indicative research activity, M., 1958; Magun G., The Waking Brain, trans. from English, M., 1961; Chauvin R., Animal Behavior, trans. from French, M., 1972, ch. 6.

N. D. Agracheva.

Great Soviet Encyclopedia, TSB. 2012

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The animal's reaction to novelty was first studied and called the orienting reflex in the school of I.P. Pavlova. It was shown that the occurrence of the orienting reflex is not associated with the sensory modality of the stimulus, that it can be subjected to extinction, and the mechanism of the latter is the generation of internal inhibition, that for all that it is innate, i.e., unconditioned, and is preserved in animals deprived of the cortex cerebral hemispheres, acquiring in this case special durability and inextinguishability (N.A. Popov, 1921, 1938; S.N. Chechulin, 1923; I.S. Rosenthal, 1929; G.P. Zeleny, 1930).

Initially, the orienting reflex was only the motor reaction of the animal towards a new or unusual stimulus (turning the head, moving the ears and eyes, etc.). Subsequently, a broader point of view became widespread, according to which the orientation reflex is a whole system of reactions integrated in a complex somatic-getative complex (E.N. Sokolov, 1958a, b; O.S. Vinogradova, 1959, 1961). Thus, the orienting reaction can be studied both by motor and vegetative and electrographic indicators, which, however, are not always consistent with each other (for example, the rate of extinction of various components of the orienting reaction may be different in the same subject).

The indicative reaction can be characterized by a number of parameters, each of which has a special functional value, apparently, does not always coincide with the meaning of others. Regarding each of them, one can assume a varying degree of connection with certain features of the nervous system. What are these parameters?

One of them is the threshold of the orienting reflex. Since the latter is always the result of sensory stimulation, the question arises about the minimum value of the stimulus that evokes a response in the form of an indicative reaction. Many authors have found that the threshold of the orienting reflex (mainly according to galvanic skin and electroencephalographic indicators) actually coincides with the threshold of sensation determined by the verbal reaction, in any case, before the orienting reaction begins to fade away upon repeated presentation of the stimulus (G.V. Gershuni, 1955; A. J. Derbyshire, J. S. Farley, 1959). But the threshold of sensation (see more about this below) reveals a connection with the strength of the nervous system (B.M. Teplov, 1955; V.D. Nebylitsyn, 1959a; V.I. Rozhdestvenskaya et al., 1960). Consequently, the threshold for the occurrence of an indicative reaction should correlate with indicators of the strength of the nervous system (relative to arousal).

Unfortunately, so far there has been no direct comparison of the corresponding indicators in the experiment, although, probably, the use of this technique would be useful in studying the relationship between sensitivity and strength of the nervous system in animals.

In a typological context, another parameter of the indicative reaction can be studied - its magnitude. Determining this parameter presents some difficulties, since the magnitude of the orienting reaction naturally decreases as presentations are repeated. Therefore, to take into account the magnitude of the orienting reflex, it is necessary to use one of the following indicators that approximately correspond to the task: 1) the magnitude of the reaction to the first presentation of a new stimulus, 2) the average magnitude of the reaction to a certain pre-fixed number of presentations of the stimulus, and finally, 3) the characteristic of the steepness of the curve depicting on the graph dynamics of extinction of the orienting reaction (function gradient). The simplest of these indicators is the first, and, as we will see later, it works quite well.

Finally, the third main parameter of the orienting reaction is the rate of its extinction with continued repetition of the stimulus. Extinction can be carried out to a certain, predetermined criterion, for example, until there is no response in a series of three or more presentations in a row (acute extinction) or until there are no responses in several successive trials (chronic extinction). This procedure closely resembles the extinction of a conditioned reflex. I.P. Pavlov assumed that it was also accompanied by the development of internal inhibition (1951–1952, vol. IV, p. 269) and, perhaps, in a physiological sense, means the same thing as the extinction of a conditioned reaction. Since, however, the orienting reflex is an unconditioned reaction, many foreign authors prefer to use the terms “habituation” and “adaptation” instead of the term “extinction.”

As already mentioned, each of the listed basic parameters of the orienting reaction probably has a typological significance, that is, it depends on some properties of the nervous system. Unfortunately, in Pavlov’s school - as during the life of I.P. Pavlov, and after his death - no systematic studies were carried out on the individual characteristics of orienting reactions, as well as the possible connection of these characteristics with the properties of the nervous system, although the data obtained along the way by some of the above-mentioned authors undoubtedly gave reason to think that that a number of features of the dynamics of the orienting reflex also reflect the properties of the animal’s nervous system. The available direct data on the comparison of the properties of the orienting reaction with the properties of the nervous system can be systematized as follows.

In 1933 N.V. Vinogradov described a dog of a weak type, which, according to the author’s observations, was characterized by an unquenchable orientation reflex. Since then, in the literature (M.S. Kolesnikov, 1953) there is an opinion that animals with a weak type of nervous system are characterized by an undying orienting reaction to any stimuli external environment. Thus, according to this point of view, the rate of extinction of orientation is a function of the strength of the nervous system.

Another point of view (L.N. Stelmakh, 1956) connects the speed of extinction of the orienting reaction not with the strength of the nervous system, but with the mobility of nervous processes (determined by the speed of alteration). L.N. Stelmakh points out that, on the one hand, an unquenchable orienting reaction can also occur in dogs strong type, and on the other hand, extinction of orientation can be easily achieved in dogs with a weak nervous system. At the same time, a certain dependence of the rate of extinction on the property of mobility is revealed (although with significant exceptions). Unfortunately, the author does not provide quantitative values for the connection between the extinction of orientation and alteration. A significant drawback of the work is also that the study of the orienting reaction was carried out after the type of nervous system in dogs was determined, i.e., after many months of work with a variety of external stimuli.

E.A. Varukha (1953), comparing the dynamics of orienting reactions in dogs with the results of determining the properties of the nervous system using a small standard, found that an indicator such as a change in the value of the orienting reflex when the stimulus intensifies can be taken to assess the strength of the nervous system (relative to excitation), and the speed of extinction of orientation is not related to the strength of the nervous system relative to inhibition.

Works performed by L.G. Voronin, E.N. Sokolov and their employees (L.G. Voronin, G.I. Shirkova, 1949; L.G. Voronin, E.N. Sokolov, 1955; E.N. Sokolov et al., 1955; L.G. Voronin and al., 1959; W. Bao-Hua, 1958, 1959), drew attention to another aspect of the typological conditionality of orienting reactions, namely their connection with the balance of nervous processes. At the same time, as already indicated in Chap. II, although the authors talk about balance in strength, analysis of the tests they use allows us to conclude that we are talking, rather, about what we designate as balance of nervous processes in dynamism. Thus, in the work of W. Bao-Hua (1959), the referent indicator of balance was the number of erroneous actions when developing an elementary motor stereotype according to preliminary instructions, more precisely, the ratio of errors when presenting positive and negative components of the stereotype.

Neither this nor other tests provided for by N.A.’s methodology. Rokotova (1954), applied in this case by W. Bao-Hua, generally cannot give indicators of the strength (endurance) of the nervous system regarding excitation, as well as regarding inhibition, but some of them can be interpreted as reflecting the level of dynamism of nervous processes. In most of these works, we are talking about the rate of extinction of galvanic skin reactions, and the assumptions are that the rapid extinction of orientation according to the galvanic skin indicator indicates the predominance of the inhibitory process, and the slow extinction of GSR indicates the predominance of the excitatory process. The same assumption is contained in the work of A. Mundy-Castle and B. McKeever (A.S. Mundy-Castle, B. Z. McKiever, 1953), also performed using the galvanic skin indicator.

So, different authors associate certain indicators of the orienting reflex with various properties of the nervous system, and, as you can see, the main interest is in the speed of extinction of the reaction. What can you say about this?

The role of the strength of the nervous system in some characteristics of the orienting reaction can hardly be questioned. We have already talked about this when discussing the question of the threshold for the emergence of orientation. But the magnitude of the orienting reaction, apparently, also cannot, to some extent, not depend on the strength of the nervous system relative to excitation. Since a strong nervous system has less sensitivity, the relationship between strength and the magnitude of orientation should be inverse: individuals with a weak nervous system should have a more pronounced orientation reaction, especially when using stimuli of weak and medium intensity, which in the case of systems of different sensitivity will provide the greatest differences in physiological effect. Perhaps this is one of the reasons for the higher orienting activity, the “unquenchable” orienting reflex in some individuals of a weak type of nervous system - but, probably, only one of the reasons, and not the most significant one.

As for the connection between indicative reactions and the mobility of nervous processes, the available materials (L.N. Stelmakh, 1956) are insufficient to draw any definite conclusions on this issue. This, of course, does not mean that the assumption of such a connection should be rejected out of hand. This only means that it must be tested in an experimental comparison of relevant indicators.

The most substantiated views seem to be those that link some parameters of the orienting reaction with the balance of nervous processes (we would say, with balance in dynamism). At the same time, it may be necessary to keep in mind that the dynamism of the excitatory and the dynamism of the inhibitory processes, reflecting functionally different properties of the nervous substrate, can have different effects on different aspects of the orienting reflex.

As for the rate of extinction of orientation, it can be assumed to be a direct function of the dynamism of the inhibitory process. As already noted, I.P. Pavlov and his colleagues pointed out that the effect of extinction of the orienting reflex is completely similar to the effect of extinction of the conditioned reflex: similarities are observed both in the details of the processes themselves and in their results - both of them lead to the emergence of a drowsy and sleepy state, which owes its origin to the irradiation of the developed internal inhibition.

Analysis of the electrographic manifestations of the orientation reflex allowed E.N. Sokolov (1963) and O.S. Vinogradova (1961) put forward the assumption that the extinction of the orienting reaction itself is nothing more than a gradually developed conditioned reflex process, in which the conditioned stimulus is the beginning of the applied stimulus, which becomes a signal of its certain duration and its absence in the background.

Thus, the extinction of the orienting reflex leads to the formation of an inhibitory functional structure in the same way as the extinction of a conditioned reaction, which, as expected, leads to an increase in the selective activity of inhibitory synaptic apparatuses (E.N. Sokolov, N.P. Paramonova, 1961; P. V. Simonov, 1962). Just as in the case of a conditioned reaction, this inhibitory functional structure apparently develops primarily in the cerebral cortex: removal of the cortex, according to data obtained back in the school of I.P. Pavlova (G.P. Zeleny, 1930; N.A. Popov, 1938), and data newest works(M. Jouvet, 1961), leads to the elimination of the mechanism of extinction of the orienting reaction, as a result of which, as E.N. points out. Sokolov (1963), the orienting reflex turns into the actual unconditioned reflex, devoid of conditioned reflex components and therefore not amenable to extinction.

Based on these data and considerations, we assume that the extinction of the orienting reaction, as well as the extinction of the conditioned reaction, is a function mainly of that property of the nervous system, which we designate as the dynamism of the inhibitory process: high level the dynamism of inhibition leads to a rapid extinction of orientation; at a low level of this property, the extinction of orientation can be a very long process. Let us note again that the latter phenomenon may probably be a consequence not only of the low dynamism of the inhibitory process, but also of the high absolute sensitivity of the analyzer that perceives the sensory stimulus, which, falling on this system, obtains greater physiological effectiveness; high sensitivity is inherent in a weak nervous system.

Some parameters of the orienting reaction may also depend on the dynamics of the excitatory process. In particular, the influence of the latter can be assumed in the magnitude of the orienting reaction at the first presentation of the stimulus. Indeed, if subsequent presentations of it lead to the development of conditioned inhibition, limiting the emerging excitation, then when the stimulus is first applied, this limitation has not yet been developed, or, in any case, not sufficiently. Therefore, the excitation that occurs during the first presentation of a signal, when the mechanisms of conditioned inhibition have not yet come into effect, will probably be characterized by greater amplitude, intensity and duration. Hence, in individuals with high dynamics of the excitatory process, we can expect more pronounced (in magnitude) indicative reactions to the first inclusion of a stimulus compared to individuals with low dynamics of the excitation process.

Based on some of the assumptions made, certain experimental data were obtained in the psychophysiology laboratory. Since these data each time have their own specifics according to the methodology used, we will consider them in several sections, devoting each to one of the methods used.

Sensory orienting reactions. A specific feature of sensory orienting reactions, i.e. changes in sensation thresholds (in our case, absolute thresholds) occurring according to the rules of the orienting reflex, is that in addition to the above parameters - threshold, magnitude and rate of extinction - they also have a direction parameter: indicative the reaction can be expressed either in a decrease or in an increase in absolute sensitivity, varying in this quality from subject to subject.

The work of L.B. Ermolaeva-Tomina (1957, 1959) showed this with complete certainty, which made significant amendments to the materials of L.A. Chistovich (1956), who noted only an increase in absolute thresholds during the initial action of side stimuli, and E.N. Sokolov (1958a), who found in his subjects only a decrease in thresholds under the influence of stimuli causing an indicative reaction.

L.B. Ermolaeva-Tomina studied both the influence of collateral light stimuli (flickering light) on auditory thresholds and the effect of collateral sound stimuli (intermittent sound) on visual thresholds ( detailed description For techniques, see the indicated works by L.B. Ermolaeva-Tomina). The approximate nature of the influence of these stimuli is proven, firstly, by the fact that these shifts are extinguished upon repeated presentations, secondly, by the fact that with further presentations these shifts acquire the opposite direction and are now stationary in nature, and thirdly, by the fact that that approximate shifts in thresholds also occur when a constantly acting side stimulus is turned off, as well as when the order of stimuli is changed.

It is important to note that the manifestation of the found patterns apparently does not depend on the analyzed analyzer: if the subject tends to lower the auditory threshold when exposed to pulsating light, then the influence of intermittent sound on the visual threshold will also mostly be expressed in him in a decrease in the measured threshold.

The main correlation obtained by L.B. Ermolaeva-Tomina in comparison with the properties of the nervous system, lies in the dependence of the direction of the approximate shift in sensitivity on the strength of the nervous system in relation to excitation. It was found that subjects with a strong nervous system react to the first and subsequent (before extinction) presentations of an additional stimulus, as a rule, by decreasing absolute sensitivity, while in “weak” subjects under the same conditions sensitivity in the vast majority of cases increases. Individual exceptions, inevitable when studying unselected groups, only confirm the general rule.

But the influence of the strength of the nervous system affects not only the direction of shifts in absolute sensitivity. Comparison of group averages leads to the conclusion that, in addition to the direction of shifts, the groups of “strong” and “weak” subjects also differ in the magnitude of these shifts: average absolute value changes in sensitivity in subjects with a weak nervous system are noticeably greater than in subjects with a strong nervous system.

Thus, in “strong” subjects the sensory orienting reaction proceeds like an external brake, while in “weak” individuals the orienting reaction leads to an improvement in the sensory function under study. These apparently paradoxical results require an explanation, which is provided by L.B. Ermolaeva-Tomina puts forward the following assumption: “With weak cortical cells... the indicative reaction obviously causes more generalized excitation, which manifests itself in an increase in the sensitivity of the analyzers. The decrease in sensitivity during the orienting reaction in subjects with strong cortical cells can probably be explained by the fact that their excitation is very quickly localized in the analyzer to which the extra-stimulus is directly addressed” (1959, p. 102). In principle, we can agree with this explanation if we add to it some missing links relating mainly physiological mechanisms the indicated differences.

One can definitely think that these differences are associated with the difference in the absolute sensitivity of the strong and weak nervous systems. A weak nervous system, having a lower threshold of sensation, probably also has a lower threshold for excitation of the nonspecific activating system. It can be assumed that, due to this circumstance, a weak nervous system retains the tonic nature of generalized activation longer, provided by the mesencephalic part of the reticular system.

On the contrary, under the same conditions, a strong nervous system with its higher threshold, leading to a relative decrease in the physiological effect, perhaps already during the interval of action of the side stimulus (20 - 30 s) moves to a phasic form of activation, usually associated with the thalamic nonspecific system. And, as is known, a feature of thalamic activation is its localization in the structures of the irritated analyzer (S. Sharpless, N. Jasper, 1956; A.Yu. Gasteau et al., 1957; E.N. Sokolov, 1958a). One can imagine how L.B. suggests this. Ermolaev-Tomin that in the first moments of the action of a side stimulus on a strong nervous system, in it, as in a weak one, generalized activation also takes place, accompanied by an increase in sensitivity to the testing stimulus. Since, however, it is very short in nature, the experimenter simply does not have time to measure and register its peripheral effect. After a few seconds, when the activation reaction has already been transferred to the thalamic level and is localized within the narrower boundaries of cortical projections, in the area of the analyzer that receives the testing threshold stimulus, perhaps, due to the mechanisms of sequential induction, a drop in excitability and thereby a decrease in sensitivity to the testing stimulus is observed.

Of course, all these considerations are very hypothetical in nature and require further experimental and theoretical justification.

So, one of the parameters of sensory orienting reactions - their direction (and perhaps, if we keep in mind their magnitude - two) - reveals a fairly definite connection with such a property of the nervous system as its strength in relation to excitation. Unfortunately, we cannot say anything as definite about the role that other properties of the nervous system play in sensory orienting reactions, since the necessary comparisons have not been made in the laboratory, and, as far as we know, there are no literary data on this issue. In this regard, more material was obtained from the study of vascular reactions.

Vascular orientation reactions. Work on the study of vascular (vasomotor) orientation and conditioned reflex reactions was undertaken in the laboratory of psychophysiology of V.I. Rozhdestvenskaya (1963 b) specifically for the purpose of studying the capabilities of this technique in studying the properties of the human nervous system. The main problem that arises when working with the plethysmographic technique is the difficulty of establishing in many subjects the so-called zero plethysmographic curve, i.e., a smooth background devoid of spontaneous fluctuations. True, this seems to apply more to the more sensitive plethysmogram of the finger, rather than the hand (A.A. Rogov, 1963), but even in this latter case, pronounced spontaneous undulation can be observed, masking reactions to the stimuli used in the experiment.

It must be pointed out, however, that the very nature of the original, background curve, as shown by V.I. Rozhdestvenskaya and a number of other authors, can serve as an indicator of such quality as the balance of excitatory and inhibitory processes. The question arises: what kind of balance is this? Is this a balance in the Pavlovian sense of the term, i.e. the balance of nervous processes in some higher levels of the nervous system, or perhaps the undulation of the plethysmogram reflects only the imbalance of dynamic vasoconstrictor and vasodilator influences interacting in the subcortical vasomotor centers or even directly on the periphery?

Data from V.I. Rozhdestvenskaya testifies, rather, in favor of the first assumption. These data were obtained on 25 adult normal subjects when recording a digital plethysmogram. The experimental program included: 1) testing the effect of neutral sound (400 Hz tone) stimuli of different intensity, 2) testing the effect of “unconditional” cold stimulation (ice) and 3) developing conditioned vasoconstrictor vascular reactions by combining a sound stimulus, the indicative reaction to which was to at this point is extinguished, with a reinforcing cold agent.

Thus, the features of the background curve and the process of extinction of orientation could be compared with the properties of the dynamics of the excitatory process, determined using the vasomotor technique. In addition, the magnitude and latency of reactions to both types of stimuli applied were measured. So, with regard to orientation, two of its parameters were studied here: magnitude (average of the first 10 presentations of the sound) and rate of extinction.

The peculiarity of the work was that all four intensities of the sound stimulus used to extinguish the orientation (from near-threshold to very strong) were presented separately and in random order and, thus, it was possible to compare the progress of the extinction of the orienting reaction at different stimulus intensities. It turned out (see Table 2, borrowed from the work of V.I. Rozhdestvenskaya, 1963b) that the volume of sound very significantly affects the speed of extinction of orientation: with a very loud stimulus, the extinction criterion (5 inhibitory reactions in 5 consecutive presentations of this stimulus) is not was achieved in 25 subjects, with loud – in 7 subjects, with medium and quiet – only in 1.

The clearest individual differences are observed at the average intensity of the stimulus, to which 5 subjects did not observe any reaction, and the maximum number of presentations before the response was extinguished was 20 (1 subject had more than 20). For this reason, and also because conditioned reactions were developed to a stimulus of precisely this intensity, to determine the connection between the rate of extinction of orientation and the speed of development of the conditioned reflex, we took individual indicators obtained at this average intensity.

table 2

The number of presentations of a sound stimulus of varying intensity until the indicative vascular reaction is extinguished (V.I. Rozhdestvenskaya, 1963b)

ORIENTING RESPONSE (eng. orienting response) - a multicomponent reflex (involuntary) reaction of the human and animal body, caused by the novelty of the stimulus. Syn. orientation reflex, exploratory reflex, “What is it?” reflex, activation reaction, etc. In the complex of components of the O. r. include: 1) movements of the head, eyes and (in many mammals, also ears) in the direction of the source of irritation (motor component), 2) dilation of brain vessels with simultaneous narrowing of peripheral vessels, changes in breathing and electrical muscle tone (vegetative component), and also 3) an increase in the physiological activity of the cerebral cortex, manifested in the form of a decrease in the amplitude of the alpha rhythm, the so-called. depression of the electroencephalogram (neurophysiological component), 4) increase in absolute and/or differential sensory sensitivity, including an increase in the critical frequency of flicker fusion and spatial visual acuity (sensory component). (See Attention, Attention physiological mechanisms.)
O. r. has a pronounced dynamics over time. Initially, when a new stimulus is presented, all components of the OR are manifested, forming the so-called. generalized O. r. At the same time, depression of the alpha rhythm is recorded in many areas of the cortex. After 15-20 presentations of the same stimulus, some of the components of the OR. fades away. Depression of the alpha rhythm is recorded only in the cortical projection of the corresponding analyzer. This phenomenon is called local OR. With further presentation of the intrusive stimulus, even local O. r. fades away; the irritant, having long ceased to be new to the body, continues to cause only the so-called. evoked potentials of the cerebral cortex: this suggests that nerve impulses caused by an external stimulus reach the cortex even after the complete extinction of the OR.
A distinctive feature of the extinction of O. r. - selectivity in relation to the stimulus. A change in the characteristics of the stimulus after extinction has been achieved leads to the appearance of O. r. as a response to novelty. By changing different stimulus parameters, it can be shown that the selectivity of extinction of O. r. manifests itself in the intensity, quality, duration of the stimulus and the intervals used. In each case, O. r. is the result of mismatch signals that arise when there is a mismatch between the stimulus and its neural model, which was formed during multiple repetitions of the stimulus used during extinction. After the presentation of a new stimulus, the OR is temporarily restored. to a habitual stimulus: disinhibition occurs. The similarity of the extinction of O. r. with the extinction of the conditioned reflex gave I.P. Pavlov reason to believe that both processes are associated with the development of internal inhibition. Considering the extinction of O. r. as the development of inhibitory conditioned reflex connections, we can conclude that it is negative learning.
Study of neural mechanisms of O. r. showed that it is associated with neurons located outside the main sensory pathways in the reticular formation and hippocampus. In contrast to specific afferent neurons, which are characterized by stable reactions even over many hours of stimulation, neurons associated with OR are unique detectors of novelty. These are multisensory neurons that respond only to new stimuli. The extinction of the reactions of novelty detectors repeats at the neural level the basic patterns of OR. and is characterized by a high degree of selectivity. See Information Needs.

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English orienting response) is a multicomponent reflex (involuntary) reaction of the human and animal body caused by the novelty of the stimulus. Syn. orientation reflex, exploratory reflex, “What is this?” reflex, activation reaction, etc. In the complex of components of the O. r. include: 1) movements of the head, eyes and (in many mammals, also ears) in the direction of the source of irritation (motor component), 2) dilation of brain vessels with simultaneous narrowing of peripheral vessels, changes in breathing and electrical muscle tone (vegetative component), and also 3) an increase in the physiological activity of the cerebral cortex, manifested in the form of a decrease in the amplitude of the alpha rhythm, the so-called. depression of the electroencephalogram (neurophysiological component), 4) increase in absolute and/or differential sensory sensitivity, including an increase in the critical frequency of flicker fusion and spatial visual acuity (sensory component). (See Attention, Attention physiological mechanisms.)

O. r. has a pronounced dynamics over time. Initially, when a new stimulus is presented, all components of the OR are manifested, forming the so-called. generalized O. r. At the same time, depression of the alpha rhythm is recorded in many areas of the cortex. After 15-20 presentations of the same stimulus, some of the components of the OR. fades away. Depression of the alpha rhythm is recorded only in the cortical projection of the corresponding analyzer. This phenomenon is called local OR. With further presentation of the intrusive stimulus, even local O. r. fades away; the irritant, having long ceased to be new to the body, continues to cause only the so-called. evoked potentials of the cerebral cortex: this suggests that nerve impulses caused by an external stimulus reach the cortex even after the complete extinction of the OR.

A distinctive feature of the extinction of O. r. - selectivity in relation to the stimulus. A change in the characteristics of the stimulus after extinction has been achieved leads to the appearance of O. r. as a response to novelty. By changing different stimulus parameters, it can be shown that the selectivity of extinction of O. r. manifests itself in the intensity, quality, duration of the stimulus and the intervals used. In each case, O. r. is the result of mismatch signals that arise when there is a mismatch between the stimulus and its neural model, which was formed during multiple repetitions of the stimulus used during extinction. After the presentation of a new stimulus, the OR is temporarily restored. to a familiar stimulus: dissolution of the O. r. The similarity of the extinction of O. r. with the extinction of the conditioned reflex gave I.P. Pavlov reason to believe that both processes are associated with the development of internal inhibition. Considering the extinction of O. r. as the development of inhibitory conditioned reflex connections, we can conclude that it is negative learning.

Study of neural mechanisms of O. r. showed that it is associated with neurons located outside the main sensory pathways in the reticular formation and hippocampus. In contrast to specific afferent neurons, which are characterized by stable reactions even over many hours of stimulation, neurons associated with OR are unique detectors of novelty. These are multisensory neurons that respond only to new stimuli. The extinction of the reactions of novelty detectors repeats at the neural level the basic patterns of OR. and is characterized by a high degree of selectivity. See Information Needs.

Approximate reaction. Study of the orienting reaction

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