Higher nervous activity of the brain. central nervous system
Higher nervous activity represents the integrative ability of the higher parts of the brain to provide a person’s individual behavioral adaptation to changing conditions of the internal and external environment. The theory of higher nervous activity is built on the following basic basis:
1. on the concepts of reflex theory,
2. on the theory of reflection,
3. on the theory of systemic activity of the brain.
The physiological basis of the processes of higher nervous activity is the analytical-synthetic activity of the cerebral cortex.
Analytical activity of the cortex The brain lies in its ability to separate, isolate and distinguish between individual stimuli, that is, to differentiate them.
Synthetic activity of the cortex cerebral hemispheres manifests itself in the unification, generalization of excitation that arises in its various parts from the action of various stimuli.
Analysis and synthesis of specific signals constitute first signaling system humans and animals. Second signaling system- these are nervous processes that arise in the hemispheres of the human brain as a result of the perception of signals from the surrounding world in the form of speech notations. The second signaling system is the basis of human thinking; it is socially conditioned. Outside of society, without communication with other people, it does not develop. The first and second signaling systems are inseparable from each other; they function together and determine the unity of human higher nervous activity.
GNI research methods
1. Method of conditioned reflexes.
2. Electroencephalography – registration of the total electrical activity of the brain from the surface of the head. The EEG records 4 main physiological rhythms: ά-, β-, θ- and δ- rhythms.
3. The method of evoked potentials - registration of fluctuations in electrical activity on the EEG during a single stimulation of peripheral receptors.
4. Computed tomography – radiographic image of each part of the brain from different points.
5. Nuclear magnetic resonance – registration of the appearance and attenuation of electromagnetic resonance radiation from the nuclei of hydrogen atoms.
6. Magnetoencephalography – recording the voltage of magnetic fields.
7. Rheoencephalography – registration of changes in the resistance of brain tissue to high-frequency alternating current depending on blood supply.
8. Galvanic skin response - measurement of changes in skin resistance under the action of an irritant.
Human behavioral reactions
Forms of behavior of the human body are usually divided into congenital and acquired in the process of ontogenesis. Innate forms of behavior are based on unconditioned reflexes and instincts.
Instincts is a genetically developed form of behavior carried out under the influence of basic biological needs. Human instinctive activity is based on innate connections between the subcortical centers and the cerebral cortex.
Unconditioned reflex is an innate response of the body that occurs constantly in individuals of a given species and age with adequate exposure to vital stimuli on certain receptors. Thanks to unconditioned reflexes, the integrity of the body is preserved, the constancy of the internal environment is maintained, and reproduction occurs. Unconditioned reflexes include
· food reflexes (chewing, swallowing, sucking, salivation, gastric juice);
· defensive reflexes (coughing, sneezing, blinking when a foreign object gets into the eye, withdrawing a hand from a hot object);
· sexual reflexes (reflexes associated with sexual intercourse, feeding and caring for offspring);
thermoregulation reflexes;
· breathing reflexes;
· cardiac reflexes;
· vascular reflexes;
· homeostasis reflexes.
Acquired forms of behavior are based on conditioned reflex reactions.
Conditioned reflex is a response of the body acquired during life as a result of a combination of an indifferent (indifferent) stimulus with an unconditioned one.
Indifferent stimulus(signal) is a stimulus that does not cause any changes in the body.
Unconditioned stimulus(signal) is a stimulus that represents biologically significant signals. If they are present, an unconditioned reflex arises.
Conditioned reflexes ensure the body's perfect adaptation to changing living conditions and make behavior plastic. When in action conditional signal(a signal that causes a corresponding conditioned reflex) the cerebral cortex provides the body with preliminary preparation for responding to those environmental stimuli that will subsequently have an impact.
The main differences between conditioned reflexes and unconditioned ones
Conditioned reflexes (CR) |
Unconditioned reflexes (BR) |
Purchased |
Congenital |
Fickle |
Permanent |
Individual |
|
Any stimulus to any receptor field |
A specific stimulus to a specific receptor field |
Carried out at the level of the cerebral cortex |
Carried out at the level of the spinal cord, brainstem, subcortical nuclei |
Formed on the basis of BR or UR of lower order |
For the formation of a conditioned reflex, the following conditions are necessary:
1. an indifferent signal (stimulus) must precede the unconditional one,
2. the strength of the indifferent stimulus should be of medium strength (with low and high strength the reflex may not be developed),
3. there must be a sufficiently large strength of the unconditioned stimulus,
4. there must be sufficient excitability of the cells of the cerebral cortex,
5. the absence of extraneous stimuli during the development of the reflex is necessary.
The mechanism of formation of a conditioned reflex is associated with the establishment of a temporary connection
1. between two or more excited foci in the cerebral cortex;
2. between the center of conditioned stimulation in the subcortical structures of the brain and the center of unconditioned stimulation in the cortex;
3. between the cortical center of unconditional stimulation and the subcortical center of conditioned stimulation;
4. and at the level of subcortical formations.
There are three stages in the formation of a conditioned reflex:
1. stage of pregeneralization - characterized by the concentration of excitation in the projection zones of the cortex of conditioned and unconditioned stimuli and the absence of conditioned behavioral reactions;
2. stage of generalization – this stage is based on the process of irradiation of excitation;
3. stage of specialization of the conditioned reflex - characterized by the extinction of intersignal reactions and the emergence of a conditioned response to signal stimuli.
A necessary prerequisite for the formation of a conditioned reflex is the occurrence of an orienting reflex. Orienting reflex- this is an unconditional reflex, involuntary sensory attention caused by an unexpected or new stimulus for the body. The indicative reaction precedes the formation of a conditioned reflex and consists of three main phases
· the first – the phase of preventive inhibition, which consists of stopping the current activity while fixing the posture;
· second – the phase of general activation, which manifests itself in the form of a multicomponent reaction, including turning the head and eyes in the direction of the stimulus;
· third – phases of analyzing external signals and making decisions about the body’s response.
The meaning of the conditioned reflex:
· the conditioned reflex mechanism underlies the formation of any acquired skill, the basis of the learning process;
· based on a number of conditioned reflexes, a dynamic stereotype is formed, which is the basis of a person’s habits, the basis of his professional skills;
· conditioned reflexes sharply expand the number of signal stimuli that are significant for the body, which ensures a higher level of adaptive behavior.
The functioning of the conditioned reflex mechanism is based on two nervous processes: excitation and inhibition.
Braking– this is the activation of inhibitory neurons, which leads to a decrease in excitation in the centers of an already developed conditioned reflex. Inhibition of conditioned reflex activity manifests itself in the form external, or unconditional, braking and in shape internal, or conditional, braking.
External unconditioned inhibition of conditioned reflexes- this is an innate, genetically programmed inhibition of one conditioned reflex by other conditioned or unconditioned ones. There are two types of external braking: transient and inductive.
1. Extreme inhibition of the UR develops either with a high stimulus strength or with weak functioning of the nervous system. Extreme inhibition has a protective value.
2. Inductive inhibition of the SD is observed in the case of application of a new stimulus after the development of the SD or together with a known stimulus.
Biological significance of external inhibition consists in the fact that the body delays its reaction to minor events and focuses its activity on the most important ones at the moment.
Internal or conditioned inhibition- this is inhibition that occurs within the reflex arc in the event of non-reinforcement of the conditioned reflex. The biological significance of internal inhibition is that if conditioned reflex reactions to generated signals cannot provide the adaptive behavior necessary in a given situation, especially when the situation changes, then such signals are gradually canceled while maintaining those that turn out to be more valuable.
There are three types of internal inhibition of the conditioned reflex: differentiation, extinction and delayed inhibition.
1. As a result of differential inhibition, a person begins to distinguish between stimuli that are similar in their parameters and reacts only to biologically significant ones.
2. Extinction inhibition occurs when, with a conditioned reflex developed, the effect on the body of a conditioned stimulus is not reinforced by the influence of an unconditioned stimulus. Thanks to extinction, the body stops responding to signals that have lost their meaning. Fading helps to free yourself from unnecessary unnecessary movements.
3. Delayed inhibition occurs if the developed conditioned reflex is moved away in time from the unconditioned stimulus that reinforces it. Delay in children is developed with great difficulty under the influence of upbringing and training. Delay is the basis of endurance, willpower, and the ability to restrain one’s desires.
Dynamic stereotype is the highest manifestation of the analytical-synthetic activity of the cerebral cortex. A dynamic stereotype is a system of conditioned reflex acts in which each subsequent reflex is caused by the completion of the previous reflex. It is the basis of a person’s habits, the basis of his professional skills.
Motivations and emotions
Motivation is an impulse to purposeful action caused by a need. The mechanism for forming motivation consists of five steps:
1. Change in metabolic state - the emergence of a need;
2. Activation of the hypothalamic centers by the neurohumoral route;
3. Activation of other brain structures, including the cortex, by excited hypothalamic centers;
4. Excitatory and inhibitory influence of the limbic system and cerebral cortex on the hypothalamic motivational centers;
5. Cellular and molecular integration of cortical-subcortical structures.
Emotions are a person’s subjective reactions to internal and external stimuli. From a physiological point of view, emotions are an active state of specialized brain structures that encourage behavior change in the direction of strengthening or weakening a certain state. The anatomical and physiological substrate of emotions is the limbic system of the brain. Emotions have the following functions:
1. evaluative function (reflective) - consists of a generalized assessment of external and internal events;
2. motivating function - consists of calling an action aimed at satisfying a need;
3. switching function – provides a choice of competing motivations;
4. communicative function - is to convey the state to other people using facial expressions and gestures;
5. reinforcing function - consists in the fact that the positive emotion arising as a result of the performed action is a reward during learning (development of reflexes), and negative emotions contribute to the development of internal inhibition.
Motivations and emotions do not have a sharp distinction between themselves and reflect different shades of the same process.
Stress
Under emotional stress understand the body's overall systemic response to stress factors. The cause of an emotional stress reaction is not the impact itself, but the attitude towards it. The following neurohumoral structures are involved in stress reactions: hypothalamus, pituitary gland, limbic system, basal ganglia, cerebral cortex and adrenal glands.
Memory
Biological memory- this is the ability of living organisms to perceive information about irritation, consolidate and store it for the subsequent use of stored information in the organization of behavior. There is a distinction between genetic memory and acquired memory.
Under genetic (species) memory understands all the information received from parents through gametes. This memory contains information about the development of the organism. The carrier of genetic memory is DNA molecules.
Purchased (individual) memory arises in ontogenesis on the basis of life experience. It is associated with the body's adaptation to a changing environment. Individual memory is formed during the learning process and includes several processes:
· receiving the information;
· imprinting information in the form of forming a memory trace - an engram;
· saving the engram;
· reproduction of previously received information.
There are several types of individual memory:
· motor memory – remembering and reproducing movements;
· figurative memory – the basis is the memorization of objects and their properties;
· verbal-logical memory – memorization, recognition and reproduction of thoughts and concepts;
· emotional memory – remembering and reproducing sensory perceptions together with the objects that cause them.
According to the mechanism of formation, short-term and long-term memory are distinguished.
At the core short-term memory lies in the processes of reverberation of nerve impulses along closed circuits of neurons in layers III and IV of the cortex of the frontal and parietal lobes.
Long-term memory is based on structural and chemical transformations at the cellular, synaptic and systemic levels of the brain.
The activity of many brain structures is associated with memory: the reticular formation, hippocampus, amygdala, hypothalamus. For example, the hippocampus has a regulatory effect on the neurons of the neocortex, creating time-coordinated fluctuations in excitability in them. The temporal cortex is involved in the imprinting and storage of figurative information. The frontal cortex forms general behavioral programs and commands for the nearby subcortex. The thalamocortical system contributes to the organization of short-term memory. The reticular formation activates structures involved in the fixation and reproduction of engrams and itself participates in the processes of engram formation.
Sleep is an active state of the body, different in its characteristics from wakefulness. The sleep state has the following characteristics:
· loss of active communication between the body and the external environment;
· change in muscle tone;
· drop in blood pressure;
· decrease in heart rate;
· redistribution of blood in the vessels: greater filling of the abdominal vessels with blood;
· minimum level of metabolism;
· decrease in body temperature;
· changes in the electroencephalogram.
Human sleep can be monophasic (night sleep), that is, once a day, and polyphasic (day and night), which is typical for children in the first seven years of life. Night sleep lasts 7-8 hours and consists of 4-5 cycles. Each cycle begins with the phase of “slow” sleep and ends with “rapid” sleep. The duration of the cycle in an adult is approximately 60-100 minutes. In the first two cycles, “slow” sleep predominates, and in the last two cycles, “fast” sleep predominates. In an adult, “slow” sleep accounts for approximately 6.5 hours, and the “rapid” sleep phase accounts for 1.5 hours. In a newborn, REM sleep accounts for 50-60% of the total sleep duration.
During slow sleep
1. restoration processes occur in tissues, organs and systems of the body;
2. organ functions, physical and mental performance are restored;
3. growth processes are carried out;
4. processes of information ordering occur in the cerebral cortex;
5. transfer of information from short-term memory blocks to long-term memory blocks;
6. part of the information that has no biological significance is displaced from the central nervous system, which leads to a decrease in information and emotional overload.
During REM sleep, the functions of brain neurons and synapses are restored. It performs a guard function and prepares the body for the transition to a state of wakefulness.
Sleep mechanisms
Sleep occurs due to the excitation of inhibitory (hypnogenic) structures and inhibition of activating structures of the brain. It is assumed that the orbitofrontal cortex and preoptic nuclei of the hypothalamus activate the raphe nuclei, which begin to have an inhibitory effect on the reticular formation of the brainstem. When the reticular formation of the brainstem is inhibited, its inhibitory effect on the nonspecific nuclei of the thalamus weakens, due to which the cortex is inhibited and “slow” sleep develops. On the other hand, inhibition of the reticular formation of the trunk leads to the fact that its activating influence on the cerebral cortex is completely removed. This period corresponds to the appearance of REM sleep. The change from “slow” sleep to “fast” sleep is carried out using two types of neurons in the reticular formation of the pons:
· cholinergic - neurons of the REM sleep phase, which contribute to an increase in the secretion of serotonin and a decrease in the secretion of norepinephrine. In this case, sleep occurs.
· noradrenergic - neurons of the “slow” sleep phase, which contribute to the reverse process, after which a state of wakefulness occurs.
Age-related characteristics of human higher nervous activity
Development of conditioned reflexes. A child is born with a certain set of innate, unconditional reflex reactions. From the second day of life, he begins to develop conditioned connections. For example, on the 2-5th day a reaction to the feeding position is formed, an indicative reflex occurs. From the 6th day, a leukocyte conditioned reflex reaction to food intake appears. On days 7-15 of a child’s life, conditioned reflexes to sound and vestibular stimuli appear. At 2 months, reflexes from any analyzer can be developed. In the second year of life, a child develops a large number of conditioned reflexes to the relationship between the size, heaviness, and distance of objects. In the process of forming a conditioned reflex, four stages are distinguished:
· the stage of a nonspecific reaction, which is characterized by the occurrence of an indicative reaction to the stimulus;
· the stage of inhibition, during which the child’s activity is inhibited under the action of a conditioned signal;
· the stage of an unstable conditioned reflex, when conditioned stimuli do not always cause a response;
· stage of a stable conditioned reflex.
With age, the rate of development of conditioned reflexes increases. Systems of conditioned connections developed in early and preschool age (up to 5 years) are especially strong and retain their significance throughout life.
External unconditional inhibition. External unconditional inhibition appears in a child from the first days of life. At 6-7 years of age, the importance of external inhibition for higher nervous activity decreases and the role of internal inhibition increases.
Internal inhibition. Internal inhibition appears in a child approximately from the 20th day after birth in the form of a primitive form of differential inhibition. Extinction inhibition appears at 2-2.5 months, conditioned inhibition is observed at 2.5-3 months, and delayed inhibition - from 5 months.
Dynamic stereotype. In early childhood, stereotypes are of particular importance. They facilitate children’s adaptation to the environment and are the basis for the formation of habits and skills. In children under three years of age, stereotypes are easily developed and with their help the child develops the conditioned reflexes necessary for life.
Speech development. The development of speech is the process of development of the second signaling system. The timing of the development of sensory and motor speech does not coincide. The development of sensory speech precedes the development of motor speech. Even before a child begins to speak, he already understands the meaning of words. The following stages are distinguished in the development of speech:
1. Preparatory stage, or the stage of pronunciation of individual sounds and syllables (from 2-4 to 6 months);
2. The stage of the emergence of sensory speech, that is, the manifestation of the first signs of a conditioned reflex to a word, to its meaning (6-8 months);
3. The stage of the emergence of motor speech, that is, the pronunciation of meaningful words (10-12 months).
Up to 2 months, a child’s vocabulary is 10-12 words, by 18 months – 30-40 words, by 24 months – 200-300 words, by 36 months – 500-700, in some cases – up to 1500 words. By the age of 6-7 years, the ability for internal (semantic) speech appears.
Development of thinking. Visual and effective thinking is formed in preschool and primary school age. Verbal and logical thinking appears by the age of 8-9 years, reaching development by 14-18 years.
Development of behavior. The behavioral act is carried out according to two principles:
· according to the principle of reflex, that is, from stimulus to action;
· according to the principle of self-regulation - when one or another physiological indicator deviates from the level that ensures normal life activity, a behavioral reaction is activated, which restores homeostasis.
The organization of behavior involves sensory, motor, central and some neurohumoral mechanisms. Sensory systems provide recognition of stimuli from the external and internal environment. Motor systems implement a motor program in accordance with sensory information. Central systems connect sensory and motor systems to ensure adaptive behavior of the whole organism in accordance with changing environmental conditions and based on dominant motivation.
For a person, the most important behavior is communication behavior. To form communicative behavior, visual, acoustic, olfactory and tactile information is required.
· Eye contact is very important for a child to establish relationships with others. A child aged 1-1.5 weeks clearly distinguishes the general features of presented objects, and it is they, and not their shape, that are most significant for him.
· Acoustic contact is carried out in the form of speech dialogue. It is believed that a child responds to speech sounds from birth. In infants 4-5 months old, when an adult speaks, a “revival complex” of maximum strength and duration is observed, including “humming.”
· Tactile sensitivity provides the perception of external stimuli in a wide range, so for newborns and young children it has important cognitive significance. Tactile contacts are especially effective in the first trimester of life.
With age, the role of vision and hearing in ensuring communicative behavior increases. The first communicative interactions occur even before the birth of a child in the “mother-fetus” system. The connection between mother and fetus is carried out through tissue contacts. After birth, the child-mother relationship continues in the “mother-child” system. Already from the 3rd day after birth, a newborn is able to distinguish the smell of milk and the body of his mother from the smell of other people. After the 3rd month of life, the child switches to interactions with other family members. Starting from 2-2.5 years old, children can create groups of 3-4 people. Moreover, boys engage in communication more often than girls. In the presence of mothers, children prefer interaction with adults.
Literature
At birth, all living organisms have innate responses that aid in survival. Unconditioned reflexes are constant, that is, the same response can be observed to the same stimulus. But the environment is constantly changing, so the body needs to have mechanisms for adapting to new conditions, and innate reflexes alone are not enough for this. The higher parts of the brain are connected, ensuring normal existence and adaptability to constantly changing external conditions. This article is about what types of higher nervous activity there are and how they differ from each other.
What it is?
Higher nervous activity is determined by the work of the subcortex of the brain and the cerebral cortex. This concept is broad and includes several large components. These are mental activity and behavioral characteristics. Each person has his own characteristics that are different from others in behavior, views and beliefs, and habits that are formed throughout his life. The basis of these features is a system of conditioned reflexes that appear under the influence of the surrounding world, and are also determined by the hereditary characteristics of the nervous system. Academician Pavlov worked for a long period of time on the processes of VNI (this means higher nervous activity), who developed an objective methodology for studying the activity of parts of the nervous system. Also, the results of his research help to study the mechanisms that underlie this and experimentally prove the presence of conditioned reflexes.
Not everyone knows the types of higher nervous activity.
Properties of the nervous system
Basically, the transmission of the characteristics of the nervous system occurs through the mechanism of inheritance. The main properties of higher nervous activity include the presence of the following factors: strength of nervous processes, balance, mobility. The first property is considered to be the most significant, since it characterizes the ability of the nervous system to withstand prolonged exposure to stimuli. For example, on an airplane during a flight it is very noisy; for an adult this is not a very irritating factor, but for a small child with undeveloped nervous processes it can have a serious, inhibiting effect on the psyche.
The types of higher nervous activity according to Pavlov are presented below.
Strong and weak nervous system
All people are divided into two categories: the first have a strong nervous system, and the second have a weak one. With a strong type of nervous system, it can have a balanced characteristic and an unbalanced one. Balanced people are characterized by a high rate of development of conditioned reflexes. The mobility of the nervous system directly depends on how quickly the process of inhibition is replaced by the process of excitation and vice versa. People who easily transition from one activity to another are characterized by the presence of a mobile nervous system.
Types of higher nervous activity
The course of mental processes and behavioral reactions is individual for each person and has its own characteristics. The typification of the processes of nervous activity is determined by a combination of three constituent factors. Namely, strength, mobility and balance together constitute the type of GNI. In science, there are several types of them:
- strong, agile and balanced;
- strong and unbalanced;
- strong, balanced, inert;
- weak type.
What are the features of the types of higher nervous activity?
Signal systems
The course of nervous processes is unthinkable without functions associated with the speech apparatus, therefore in people there are types that are characteristic only of humans and are associated with the functioning of signaling systems (there are two of them - the first and second). With the thinking type, the body uses the services of the second signaling system much more often. People of this kind have a well-developed ability for abstract thinking. The artistic type is characterized by the dominance of the first signaling system. With the average type, the operation of both systems is in a balanced state. The physiological characteristics of the nervous system are such that hereditary factors influencing the course of mental processes in the body can change over time and under the influence of educational processes. This is primarily due to the plasticity of the nervous system.
How are the types of higher nervous activity classified?
Division into types by temperament
Hippocrates put forward a typology of people depending on their temperament. The characteristics of the nervous system allow us to say what type a person belongs to.
The sanguine person has the strongest type of higher nervous activity.
Sanguines
Their entire system of reflexes is formed very quickly, and their speech is loud and clear. Such a person pronounces words with expression, using gestures, but without excessive facial expressions. The process of extinction and restoration of conditioned reflexes is easy and effortless. The presence of such a temperament in a child allows us to talk about good abilities, moreover, he easily obeys the educational process.
What other types of human higher nervous activity exist?
Cholerics
In people of choleric temperament, the process of excitation prevails over the process of inhibition. The development of conditioned reflexes occurs with ease, but the process of their inhibition, on the contrary, is difficult. Cholerics are characterized by a high degree of mobility and the inability to concentrate on one thing. The behavior of a person with a similar temperament in most cases requires correction, especially when it comes to a child. In childhood, choleric people demonstrate aggressive and defiant behavior, which is caused by a high degree of excitability and slow inhibition of all nervous processes.
Phlegmatic people
The phlegmatic type is characterized by the presence of a strong and balanced nervous system, but with a slow transition from one mental process to another. The formation of reflexes occurs, but at a much slower pace. Such a person speaks slowly, while he has a very measured pace of speech with the absence of facial expressions and gestures. A child with such a temperament is diligent and disciplined. Completing tasks is very slow, but it is always conscientious work. Teachers and parents should take into account the characteristics of the child’s temperament during classes and daily communication. The type of higher nervous activity and temperament are interconnected.
Melancholic people
Melancholic people have a weak nervous system, do not tolerate strong stimuli well, and in response to their influence they demonstrate the maximum possible inhibition. People with a melancholic temperament find it difficult to adapt to a new team, especially children. The formation of all reflexes occurs slowly, only after repeated repetition of the stimulus. Motor activity and speech are slow and measured. They do not fuss and do not make unnecessary movements. From the outside, such a child seems timid and unable to stand up for himself.
Distinctive features
The physiological characteristics of higher nervous activity are such that for a person with any temperament it is possible to develop and nurture those qualities and personality traits that are necessary for life. Representatives of each temperament have their pros and cons. Here the process of education is very important, in which the main task is to prevent the development of negative personality traits.
A person has a second signaling system, which transfers behavioral reactions and mental processes to another level of development. Higher nervous activity is a conditioned reflex activity acquired throughout life. Compared to animals, human nervous activity is richer and more diverse. This is primarily due to the formation of a large number of temporary connections and the emergence of complex relationships between them. In the human body, higher nervous activity also has social characteristics. Any irritation is refracted from a social perspective, and therefore all activities that are associated with adaptation to the environment will have complex forms.
The presence of such an instrument as speech determines for a person the ability to think abstractly, which in turn leaves an imprint on various types of human activity. The typicality of the nervous system in humans is of great practical importance. For example, diseases of the central nervous system are in most cases associated with the course of nervous processes. People with a weak type of nervous system are more susceptible to diseases of a neurotic nature. The development of some pathologies is influenced by the course of nervous processes. The weak type of higher nervous activity is the most vulnerable.
With a strong nervous system, the risk of complications is minimal, the disease itself is much easier to tolerate, and the patient recovers faster. As for people’s behavioral reactions, in most cases they are determined not by the uniqueness of their temperament, but by the presence of certain living conditions and relationships with others. The course of mental processes can influence behavior, but they cannot be called a determining factor. Temperament can only be a prerequisite for the development of the most important personality qualities.
The central nervous system is part of the vertebrate nervous system, represented by a collection of nerve cells that form the brain and spinal cord.
The central nervous system regulates the processes occurring in the body and serves as the control center for all systems. The mechanisms of central nervous system activity are based on the interaction of excitation and inhibition.
Higher nervous activity (HNA)
Higher nervous activity - according to I.P. Pavlov - is a complex form of life activity that ensures individual behavioral adaptation of humans and higher animals to changing environmental conditions.
The basis of higher nervous activity is the interaction of innate unconditioned and conditioned reflexes acquired in the process of ontogenesis, to which a second signaling system is added in humans.
The structural basis of the VND is the cerebral cortex with the subcortical nuclei of the forebrain and some structures of the diencephalon.
Higher nervous activity
Higher nervous activity (HNA) is the activity of the higher parts of the central nervous system, ensuring the most perfect adaptation of animals and humans to the environment (behavior). The structural basis of the GNI is the cerebral cortex with the subcortical nuclei of the forebrain and the formations of the diencephalon, however, there is no strict connection of the VND with brain structures. Lower nervous activity is represented as a function of the central nervous system, aimed at regulating physiological processes in the body itself. The most important feature of GNI is its signaling nature, which allows one to prepare in advance for one or another form of activity (eating, defensive, sexual, etc.)
Characteristics of VND: variability, signaling, adaptability - provide flexibility and adaptability of reactions. The probabilistic nature of the external environment gives relativity to any behavioral reaction and encourages the body to make probabilistic forecasts. The ability to learn highly depends not only on the processes of excitation, but also inhibition. Conditioned inhibition promotes a rapid change in forms of behavior in accordance with conditions and motivations.
The term GNI was introduced by I.P. Pavlov, who considered it equivalent to the concept of “mental activity”. According to I.P. Pavlov, this is a combined reflex (conditioned and unconditioned reflex) function of the cerebral cortex and the nearest subcortex of the brain. He also introduced the concept of “signal systems” as systems of conditioned reflex connections, highlighting the first signaling system common to animals and humans and the second, specific only to humans.
The first signaling system (PSS) - direct sensations and perceptions, forms the basis of the GNI and is reduced to a set of diverse conditioned and unconditioned reflexes to direct stimuli. The human PSS is characterized by a greater speed of propagation and concentration of the nervous process, its mobility, which ensures rapid switching and formation of conditioned reflexes. Animals are better at distinguishing between individual stimuli, and humans are better at distinguishing between their combinations.
The second signaling system was formed in humans on the basis of the first as a system of speech signals (pronounced, audible, visible). The words contain a generalization of the signals of the first signaling system. The process of generalization by word is developed during the formation of conditioned reflexes. Generalized reflection and abstraction are formed only in the process of communication, i.e. determined by biological and social factors.
Receptor - (from Latin recipere - to receive), nerve formations that convert chemical and physical influences from the external or internal environment of the body into nerve impulses; a peripheral specialized part of the analyzer, through which only a certain type of energy is transformed into the process of nervous excitation. Receptors vary widely in the degree of structural complexity and in the level of adaptation to their function. Depending on the energy of the corresponding stimulation, the receptors are divided into mechanoreceptors and chemoreceptors. Mechanoreceptors are found in the ear, vestibular apparatus, muscles, joints, skin and internal organs. Chemoreceptors serve olfactory and taste sensitivity: many of them are located in the brain, responding to changes in the chemical composition of the body fluid. Visual receptors are also essentially chemoreceptors. Depending on their position in the body and the function they perform, receptors are divided into exteroceptors, interoreceptors and proprioceptors. Exteroceptors include distant receptors that receive information at some distance from the source of stimulation (olfactory, auditory, visual, gustatory); interoceptors signal about stimuli from the internal environment, and proprioceptors signal about the state of the body’s motor system. Individual receptors are anatomically connected to each other and form receptive fields that can overlap.
HIGHEST HUMAN NERVOUS ACTIVITY
Life at every step shows the immeasurable superiority of the human mind over the primitive thinking abilities of animals. The enormous gap between the mental life of humans and animals has long served as a reason for attempts to present human consciousness as a supernatural phenomenon inaccessible to objective study. However, advances in psychology and physiology of higher nervous activity provide more and more opportunities for a natural scientific explanation of the functioning of the brain of a thinking person.
The higher nervous activity of man included many achievements in the biological evolution of the conditioned reflexes of animals and, in addition, acquired systems of completely new, purely human psychological activity, operating with abstract concepts expressed in speech and forming increasingly complex verbal conditional connections. The spoken word, and then the written word, united people in joint work, helped to accumulate knowledge and reach that high level of culture on which modern man stands.
Biological prerequisites for the emergence and development of higher functions of the human brain
Studying the natural history of man's origins from the animal world dispels mystical speculations about his “divine creation.” An outstanding victory for science in this dispute was Charles Darwin’s book “The Descent of Man” (1871), which was bold at that time. He accumulated and systematized numerous convincing facts showing the genetic similarity of the structure of bodies and functions of organs of man and his anthropoid ancestors.
What in the life of anthropoids turned their evolution in this direction? The way of life in trees was apparently largely determined by the development of limbs capable of grasping branches and fruits with the help of fingers that felt objects encountered. This allowed the monkeys to manipulate them according to their needs. When, during the retreat of the forests, they descended to the ground, they could no longer return to the four-legged method of movement. Only the hind limbs, having become supporting limbs, underwent some reverse development and turned into legs, while the front limbs improved their manipulative functions even more intensively. The “four-armed” monkey turned into a two-legged ancestor of man with arms. The appearance and development of the hand was the most important biological prerequisite for the development of higher brain functions. “This was the decisive step for the transition from ape to man.”
Hand actions heralded new forms of efficient adaptive behavior that used broken branches, rocks, and a variety of objects to obtain food and fight enemies. The task of controlling the complex, precisely coordinated movements of many muscles that carried out the actions of the hands caused extraordinary development of the brain structures responsible for motor functions. Signals about this activity and information obtained during the study of objects that fell into the hands were so important that the structures of the corresponding sensory kinesthetic functions, as well as the associative functions that formed on their basis, organizing behavior, received preferential development.
The herd lifestyle of individuals who have learned to use their hands has become another important biological prerequisite for the development of higher brain functions. Based on the high perfection of sensorimotor coordination when manipulating objects in the hands and the formation of multiple direct and feedback connections during the interaction of individuals, complex forms of analytical-synthetic brain activity arose. Imitative reflexes have acquired particular importance, which are strengthened by education and determine the emergence of conditions for the development of various types of joint activities. This was facilitated by the properties of the higher nervous activity of anthropoids described in detail in the previous chapter - the speed of formation of conditioned connections, the subtlety of differentiation, the ease of developing adequate reactions to traces and complexes of signals, solving complex behavioral problems, etc. Of particular importance is the development of research and associative activity and the ability to form a rich memory fund that determines behavior in different situations.
The change in the appearance of the anthropoid who had risen to his feet especially affected the shape of his head and the size of the cerebral part of the skull. The extreme complication of mainly sensorimotor mechanisms led to the rapid development of the anterior parts of the brain and the growth of its frontal lobes, which changed the shape of the skull and caused it to protrude above the eye sockets. Among primitive people, the face had already acquired features characteristic of modern man.
Conditioned reflexes of a child
The development of the physiological activity of a child’s brain reflects the history of the formation of human thought. The behavior of an infant at first seems to consist of the usual feeding, defensive and other reflexes characteristic of animals. However, already at this time the child can detect the rudiments of a specifically human system of nervous activity, which later manifests itself in speech.
Conditioned reflexes in a newborn child. To clarify the question of when a child’s brain acquires the ability to form conditioned reflexes, a large number of experiments were carried out. Attempts to develop conditioned reflexes in an unborn fetus have led to conflicting results.
In experiments with premature infants born 1–2 months prematurely, it was possible to develop defensive conditioned reflexes of closing their eyes to a metronomic signal, accompanied by blowing on the face (N.I. Kasatkin, 1948). These reflexes were developed during the second month of postnatal life. However, the state of higher nervous activity of premature infants largely depends on the timing of prematurity, conditions of intrauterine development and a number of other reasons. Special studies have shown that the ability to develop conditioned reflexes in premature infants is in a certain relationship with the degree of development of their orienting reflex and the formation of its behavioral and autonomic components. Visual conditioned food reflexes in children who are 1–1.5 months premature are formed by the 22–39th day of postnatal life, and in 3-month premature infants - by the 59–75th day.
Attempts to develop food and defensive conditioned reflexes in newborns in the first days of life also led to contradictory results, which, apparently, reflects the uneven maturation of the nervous mechanisms of the human cerebral cortex. Only From about a week of age, the child’s ability to form conditioned reflexes becomes undeniable. By this time, the first natural conditioned reflexes can be observed in him.
Development of early conditioned reflexes in children. Some mothers claim that the baby already recognizes them at the age of one or two weeks, reaches out towards them and sucks when they take him in their arms. However, in reality, the child does not yet differentiate the people around him. Whoever picks him up in his normal feeding position, the baby will respond with the same motor response. The fact is that at about a week of age, a baby develops a natural conditioned food reflex to the feeding position. The signal here is a complex of mainly skin and proprioceptive irritations, the reinforcement is feeding (V.M. Bekhterev, N.M. Shchelovanov, 1925).
Perhaps even earlier a natural conditioned reflex during feeding is formed. Thus, if the correct time intervals between feedings are strictly observed, even in five-day-old infants one can observe the awakening and appearance of sucking movements a few minutes before each feeding period. According to other observations, if you maintain a constant feeding time, then already in 8-9 day old children there is an increase in the number of leukocytes in the blood before each feeding, i.e. development of a conditioned reaction of digestive leukocytosis.
Already during the first month of life, children can develop a variety of artificial conditioned reflexes. So, if before each feeding of 2-3-week-old infants 15 seconds before giving the breast, sound or light signals are turned on, then after a few days the inclusion of just one signal can cause sucking movements. The age at which a particular reflex was formed depended on the type of signal stimulation applied.
Reflexes formed at an early age are specialized depending on specific life circumstances, complicating and clarifying the child’s behavior. For example, the sight of a mother becomes a familiar signal of feeding, and the white coat of a doctor causing pain causes a violent defensive reaction. The child reaches for a bottle of milk and, crying, turns away from the spoon in which he receives the bitter medicine.
Development of inhibition of early conditioned reflexes in children. It takes a long time before the child really begins to recognize his mother. Only at 3–4 months of age is he able to clearly differentiate the stimuli of the complex signal for food. By this time, the reaction to the cutaneous and proprioceptive members of the signal complex will fade away, and the food reflex specializes in its visual component.
A clear differentiation of artificial visual and auditory conditioned stimuli also occurs at 3–4 months of age. Before this, attempts to develop differentiation lead to very uncertain results. Inhibition of delay was developed only when the children were 5 months old, and then with great difficulty.
Thus, the child’s brain reveals the first signs of the ability to develop different types of internal inhibition in approximately the following periods: differentiation - at 1.5-2 months, extinction - at 2-2.5 months, to develop a conditioned inhibitor - at 2.5-2 months. 3 months and delay inhibition - at 5 months.
Everyday life provides many examples of specialization and refinement of the child’s natural conditioned reflexes through various types of internal inhibition. The simplest case is the development of differentiation of visual stimuli during the specialization of the food conditioned reflex to the appearance of the mother. The development of a conditioned brake turns out to be more difficult.
For example, when porridge cooked for a child is still hot, the mother first blows on it, and then scoops it up with a spoon and feeds it to the child. In the first days of feeding, the child, upon seeing a saucer with porridge (a positive food stimulus), immediately opens his mouth and continuously reaches for the saucer. But after a few days, it is enough for the mother to blow on the saucer (additional agent) for the food reaction to temporarily stop (conditioned inhibition).
The combination of forms of inhibitory refinement of the reflex becomes more complex and diverse with age.
Motor conditioned reflexes of a child. To study the motor conditioned reflexes of children, special techniques were developed (A.G. Ivanov-Smolensky, 1933). The most widely used was the development of conditioned reflexes of grasping an object with the hand or performing a given movement. This participation of the hand in a conditioned reflex is associated with the activity of complex brain mechanisms, the work of which psychology defines as voluntary or volitional actions. They fall into various categories of adult actions. In Fig. 101 shows a setup for developing simple conditioned grasping reflexes with food reinforcement.
Rice. 101. Installation for studying conditioned grasping reflexes in children (according to A. Ivanov-Smolensky):
1 - alarm bell, 2 - tube for supplying food reinforcement (candy), 3 - glazed part of the tube, 4 - upper shutter, opened by the experimenter, 5 - lower shutter, opened by the subject, 6 - recording of the conditioned reflex movement of grasping and squeezing a rubber bulb, 7 And 8 - marks of conditioned stimulus and food reinforcement
The child is first taught to use the device. To do this, the experimenter uses a pear to open the upper pneumatic shutter of the inclined tube, along which the candy begins to slide. When the candy comes into the field of view of the subject, the latter, seeing it through the glazed part of the tube, must grab the rubber bulb and open the lower shutter. Then the candy will fall out onto the saucer, where the child can take it and eat it.
After such a conditioned reflex of opening the shutter to receive candy is developed, it is used as a reinforcer for the formation of conditioned reflexes to visual, auditory and any other signals.
Another unique form of a child’s motor conditioned reflexes are those that are developed through reinforcement by orienting-exploratory reactions. Orienting reflexes are very pronounced in children. If, for example, you turn on the bell and then show moving pictures on the screen located on the side, then soon, as soon as the child hears the bell, he turns towards the screen.
The study of motor reflexes has shown that these more mobile manifestations of a child’s mental activity are subject to the general laws of the development of excitation and inhibition, movement and induction of nervous processes according to which the higher parts of the brain operate. In these reflexes, even more than in the salivary ones, there is extraordinary progress in the development of even the general properties of nervous processes in children in comparison with the most highly developed animals, and the presence of such forms of higher nervous activity that do not occur at all in animals.
For example, an experimenter has formed a conditioned grasping reflex in a child and wants to develop differentiation of signal tones. He turns on a non-reinforced tone, and the child, instead of moving his hand, reacts with the words: “Uncle, don’t make a bad noise, give me some candy.” Having failed to reach the goal with the biological grasping reflex, the child turned to a purely human means of signaling - the word.
Mastering speech is a turning point in a child’s life. Thus, although the motor conditioned reflexes of children are carried out according to the general laws of higher nervous activity, one can also find in them such manifestations that constitute an exclusive feature of a person, primarily speech reactions.
The second signaling system of the human brain
While the child’s brain carried out even very complex food, defensive, orientation and other conditioned reflexes, his work did not yet go beyond the boundaries of the common laws of adaptive biological activity with animals. But very soon this form of behavior is overshadowed by the manifestations of a fundamentally new reflex mechanism, characteristic only of man, which finds its most complete expression in oral and written speech.
Human “gain” of nervous activity. The fundamental feature of the mental activity of the human brain, which distinguishes it from all animals, is the presence of consciousness in humans. Human consciousness is characterized by the formation of generalized and abstract complexes of conditioned stimuli - concepts expressed in words.
Human consciousness arose as a result of the fact that the biological struggle for existence and the “consumer” form of animal behavior were replaced by a social way of life and the creative work activity of people. Therefore, animals’ mental perception of natural stimuli as the sum of immediate nutritional, defensive, etc. signals was replaced by a person’s holistic perception of the surrounding world in terms created by history and the needs of human society. That is why there is such a sharp boundary between the exclusively objective, concrete thinking of animals and the always abstracting, idea-creating consciousness of man.
Thanks to consciousness, a person can mentally compare, try, come to new conclusions and, having drawn up a certain plan, be guided by it in actions. Animals are not capable of premeditated activities according to a plan. Although “the bee’s construction of its wax cells puts some human architects to shame. But even the worst architect differs from the best bee from the very beginning in that, before building a cell of wax, he has already built it in his head.”
Human consciousness is most clearly manifested in speech. Speech arose as a means of communication between people who, when working together, “appeared need to say something each other". With words, people express thoughts, convey knowledge, and encourage certain actions. A person thinks in words without even saying them. It is impossible to imagine a person’s mental life without the use of speech - oral, written, mental. No animal is capable of exchanging thoughts by talking; this is a purely human ability.
So, The higher nervous activity of animals is limited to conditioned reflexes to specific signals of food, danger, etc., in the higher nervous activity of humans, in addition, conditioned reflexes appear to general concepts expressed in words. The first category of reflexes is biological in nature, the second is social.
There are various assumptions about the origin of verbal conditioned reflexes that distinguish humans from animals. Previously, it was believed that they are formed by “stringing” signal on signal according to the type of conditioned reflexes of the second, third, fourth, etc. order. It was believed that this is how conditional chains of connections arise, which become increasingly longer with age.
It was assumed, for example, that a small child first forms a simple conditioned reflex - associates the type of food with food. Then he begins to speak and associates words with the food that indicate its name. Then he learns from adults that food needs to be bought, and associates the concept of earning money with them.
Many human concepts and impulses were explained as having developed from a natural food conditioned reflex. Other chains of connections, according to this idea, appear on the basis of protective reflexes. For example, a prohibition, reinforced by punishment in childhood, forms the concept of “no” and the associated norms of human behavior.
However, this idea, like all others that connect the emergence of verbal reflexes with biological factors, contradicts what is known about the nature of speech: obviously, speech did not arise from animal instincts, but as a result of the joint work of people. That is why a person’s consciousness, his thoughts and behavior are determined not by fear and hunger, but by the interests of human society.
Based on all the above considerations, I.P. Pavlov divided human conditioned reflexes into two fundamentally different categories. Conditioned reflexes to specific signals constitute the first signaling system of brain activity, common to humans and animals, and verbal conditioned reflexes form the second signaling system of brain activity, peculiar only to people.
The difference in the properties of the activities of the first and second signaling systems. The characteristic features of the conditioned reflex mechanism of the first signaling system are: 1) the specificity of the signal (this or that phenomenon of the surrounding reality), 2) the unconditional basis of reinforcement (food, protective or sexual meaning), 3) the biological nature of the adaptation achieved (to the best nutrition, defense, reproduction). These same characteristic features are also characteristic of the child’s first signaling system.
Conditioned reflexes of the second signaling system arise on the basis of a different physiological mechanism, other driving forces with the involvement of conceptual and moral categories. For example, hearing cries for help, a person saves a drowning man. The verbal signal given by the drowning man evoked complex second-signal conditioned reflexes in his savior. What are the characteristic features of the reflexes of the second signaling system?
1. In contrast to the concreteness of the signal in the reflexes of the first signal system, the word is an abstract signal. It acts not with its sound, but with the concept contained in it. A drowning person could call for help in different words. They sounded differently, but the thought contained in them reached everyone who heard the call.
The fact that a word acts not by its sound shell, but by its internal content, was convincingly proven by experiments with synonymous words. For example, if you develop a conditioned reflex in a person to withdraw his hand to the word “fire,” then you can say “flame” and the subject will withdraw his hand. It is clear that it is not a matter of sounds, but of the meaning of words. Nothing like this can be obtained in experiments with animals. There, the signal is a once and for all specific sound.
A word as an abstract stimulus causes conditioned excitation not of just one analytical point, but of their complex complex with the participation of many analyzers.
2. While food, defensive, and sexual reflexes serve as reinforcements in the first signaling system, in the reflexes of the second signaling system, concepts expressed in words are reinforced by what a person sees, hears, does himself and discusses with other people. Only in this way could a connection be formed between a call for help and immediate actions to save a drowning person, with actions that not only do not provide immediate biological benefit to the rescuer, but are even associated with a risk to his life. It is not for nothing that such moral actions are called truly human.
3. Finally, while the conditioned reflexes of the first signaling system provide direct satisfaction of the biological needs of the individual, conscious human activity is aimed at ensuring the vital needs of each person through the benefit of people and all of humanity. Therefore, in a person’s conscious actions, the motives of social duty and mutual assistance appear primarily.
In terms of all the properties of activity, the driving forces of its formation and development, the second signaling system is fundamentally new. Signaling with the help of words opened up opportunities for progress inaccessible to animals to humans. The word allowed each person to benefit from the life experience of all humanity and, at the same time, to make each of his achievements a universal property, to accumulate and multiply knowledge, to transfer it in the form of ready-made concepts to younger generations. Writing further expanded the possibilities of speech, facilitated the continuity of culture and helped humanity reach modern heights of science, technology, art and social relations.
Formation of a word as a “signal of signals”. Important information about the formation of a verbal stimulus as a synthetic “signal of signals” can be provided by studying the process of speech acquisition by a child. The speech function is not innate; it is acquired through learning when the child communicates with speaking people.
Cases are described when babies carried away by wild animals remained alive and grew up, for example, in a wolf pack. Such children, when they were found, were speechless, they did not understand those around them, and their second signaling system did not function.
Learning to speak begins with the fact that the child, usually in the second half of the first year of life, begins to develop various reactions to complex stimuli, of which the word is a member. For example, they say to a child: “Clap your hands,” they take his hands, make the appropriate movement, and those around him clap their hands. In a similar way, the child is taught to answer the question: “Where is mommy?” or “Where is daddy?” look back at the mother or father, at the words “show your eyes” or “show your ears,” indicate the named parts of the body, etc. Initially, the role of the word in such signal complexes is relatively small. The defining members of the complex are statokinetic components (child’s position), visual (environment, surrounding people), sound (intonation, voice timbre). This is clearly seen from observations, the results of which are presented in table. 18.
Table 18. The significance of various members of a complex stimulus for the reaction of an 8-month-old child (according to M.M. Koltsova)
When all the statokinetic, visual and auditory members of the complex stimulus that has become the signal for movement towards the father are present, a reaction occurs. But as soon as at least one of them falls, there is no reaction. As can be seen from table. 18, this happens if you change the child's position (put him in a crib), the environment (move him from the bedroom to the dining room) or the intonation of the voice (angry tone). The verbal member of the complex in these cases is not able to provide its irritating effect.
However, further practice of verbal designation of a reaction gradually increases the role of the word among other members of the complex stimulus, the meaning of which gradually decreases. So, already 2 weeks after the experiment presented in the table, the child correctly responded to the question: where is dad? not only being in the arms of the mother, but also lying in the crib. After some time, the situation loses its meaning; the reaction occurs not only in the bedroom, but also in the dining room, and even on the street. Finally, around the end of the first year, the word is finally “liberated” from other components of the complex, and it begins to act as the main stimulus, replacing the entire complex. From a pedagogical point of view, it is important to note that the speed of the process of the formation of a word as an independent and leading stimulus is extremely dependent on the conditions of upbringing, especially on the duration and frequency of conversational communication with adults.
A possible physiological mechanism for such isolation of a verbal stimulus is the training of the strength and concentration of the nervous processes they cause with a negative induction on other members of the complex, which is facilitated by the constancy of the verbal component with endless variations of all other components in various situations of the child’s life. Remaining a natural expression of a whole complex of phenomena, the word carries out a certain degree of generalization and begins to transform from a simple sound stimulus into a speech signal.
The completion of such a transformation is determined by the accumulation of a large number of conditional connections that are sequentially formed with a given word in the child, in particular during play and orientation activities.
In the formation of these connections, the activity of the motor analyzer. Thus, the generalizing properties of a verbal stimulus turn out to be more pronounced and persistent when a certain number of conditional connections are formed for a given word from the motor analyzer than when the same number of conditional connections are formed from the visual analyzer. This explains the large role of various forms of motor, in particular play and orientation, activity. In turn, the word organizes the child’s motor activity.
The role of the motor analyzer increases enormously when the child begins to speak on his own. Each spoken word receives its expression in a certain combination of kinetic signals from the phonation apparatus, which have the same constancy that distinguished the word heard among all other members of the complex stimulus. At an older age, mastering writing adds stereotypes of kinetic signals from the movements of the writing hand and visual reading signals. The synthesis of all these signals leads to the formation of a word - a concept, a “signal of signals”, a working mechanism for the activity of the second signaling system of the human brain.
Basic properties of reflexes of the second signaling system. The features of the conditioned reflexes of the second signaling system clearly appear in comparison with the reflexes of the first signaling system, which have reached high perfection in humans. Their study, especially with verbal instructions, reveals the joint activity of these systems.
For special studies of the properties of second-signal activity, methods were developed that involved the use of verbal stimuli (A.G. Ivanov-Smolensky, 1934). Of these, the most widely used method was the development of conditioned reflexes based on speech reinforcement. For example, the experimenter gives the subject a rubber balloon connected to a pressure gauge, turns on a signal (bell, light bulb) and tells him “press the balloon.” When a connection is formed between the signal and the word, the subject performs this movement without waiting for an order. Along with what has been described, other conditioned reflexes of performing various movements to light, sound and speech signals are also used without warning or with prior verbal instructions. Protective blinking, food swallowing and various autonomic salivary, cardiovascular, sweating, photochemical and other reflexes are also used. Their technique is described in detail in a special manual (S.M. Galperin, A.E. Tatarsky, 1973).
When studying the reflexes of the second signal system, the following most characteristic properties emerged.
1. Continuous synthesis, expanding the content of verbal signals (excitation of the analyzer complex, expressing a certain concept, continuously radiates). It extends the signal meaning of this concept to all related ones, i.e. generalizes these concepts more and more widely, abstracting further and further from specific details.
This generalization clearly emerged in the following experiment. The schoolchild developed a positive conditioned salivary reflex to the word “good” with differentiation of the word “bad.” After this, phrases containing the word “good,” for example, “the pioneers had a good rest,” evoked a conditioned reflex, and the content of the word “bad” turned out to be inhibitory. Then we tested the effect of phrases in which the words “good” and “bad” were replaced by similar ones in meaning, for example, “the pioneer is doing great” or “the student is weak in his response.” A clear conditioned reaction occurred to the first phrase, but there was no reflex to the second. Finally, statements were used that only in their most general meaning spoke of good or bad. The results of this experiment are presented in table. 19.
Table 19. Conditioned salivary reflexes to verbal stimulation in a 13-year-old boy (according to V.D. Volkova)
Combination number // Conditioned verbal stimulus // Salivation, drops/30 s // Note
50 // Good // 18 // Reinforced
12 // Poor // 1 // Not supported
51 // Good // 16 // Reinforced
1 // Leningrad is a wonderful city // 15 // »
1 // The student did not pass the exam // 2 // Not supported
52 // Good // 15 // Reinforced
1 // Brother insults sister // 1 // Not supported
1 // My brother is seriously ill // 2 // » »
1 // The enemy army was defeated and destroyed // 24 // Reinforced
1 // The student passed the exam mediocre // 10 // »
From the table it is clear that according to objective indicators of the magnitude of conditioned reflexes, verbal signals “good” or “bad” continuously expanded their content up to the most general concepts of school duties “the student did not pass the exams” and patriotic consciousness “the enemy army was defeated and destroyed.”
2. Simultaneity of formation and restructuring of temporary system signals. While the temporary connections of the first signal system are developed only gradually as a result of a series of combinations, the temporary connections of verbal conditioned reflexes are formed immediately in one step. For example, you can explain to a visitor how to find the house he needs, and a person who has never been to this city will come straight to his destination (how many “trials and errors” will an animal make before finding the right path in the maze?).
The verbal cancellation of the conditioned reflex also occurs simultaneously. A person, having read the notice on the doors of the canteen “closed for renovation,” will stop going there (how many days will the dog feeding there run in vain to the back yard of the canteen until its conditioned food reflex finally goes away completely?).
All the basic acts of conditioned reflex activity are simultaneously carried out in the second signal system in the restructuring of these connections, for example, the development of differentiations (“cross the street when the traffic light is green and do not cross when the traffic light is red”), delays (“turning on the TV, wait until the image appears”) and etc. The strength of such simultaneously formed connections and the ease of their conditional renewal underlie memory.
3. Display in the second signal system of temporary connections formed in the first, and vice versa. The following observations can serve as an example.
Children developed a conditioned motor reflex to the sound of a bell. After this, in one of the experiments, instead of turning on the bell, the experimenter said the word “bell.” The subject responded to this word with the same reaction as to the sound of the bell. The inscription “bell” had the same effect when presented to the subject.
Consequently, when the human brain forms a conditioned reflex even to a specific signal of the first system, the response at the same time turns out to be associated with its verbal designation, i.e. signal from the second system. This occurs as a result of the fact that each specific signal is included as one of the members in the synthetic complex of the word.
Selective irradiation of conditioned excitation within the verbal complex from each of its members manifests itself in the form of “transfer” of connections from the first signal system to the second. Thus, both differentiations and complex relationships of stimuli can be “transmitted” up to a complete picture of the stereotype. On the contrary, the “transfer” of connections from the second signaling system to the first is revealed in the fact that conditioned reactions developed to verbal stimuli are reproduced according to the signals of specific phenomena that are denoted by a given word.
The interaction of signaling systems improves with age. Thus, children’s verbal report of specific conditioned stimuli in action becomes complete only from the age of 7–8 years.
4. The abstractness of a concept expressed in a word is inversely related to the strength of its connection with specific stimuli of reality. This property is revealed, for example, in the following experiment.
The child developed a conditioned salivary reflex to a word denoting the name of a particular bird. The magnitude of the reflex was 7–8 drops of saliva. When the generalizing word “birds” was tested, it turned out that it had a conditioned effect even stronger than the primary verbal stimulus. It gave 10 drops of saliva. However, an even broader generalization, expressed by the word “fly,” turned out to be a less powerful conditioned stimulus of the salivary reflex, the value of which dropped to 4–5 drops. Finally, the greatest degree of generalization of living beings with the word “live” resulted in only 1 drop of saliva.
Consequently, the more abstract the concept, the wider the scope of its generalization, the further it stands from reality, the weaker the connection of its verbal signal with the specific signal of the main conditioned reaction.
5. Higher fatigue and susceptibility to external influences of the reflexes of the second signaling system compared to the first. This naturally follows from the phylogenetic youth and high sensitivity of the reflexes of the second signaling system. Therefore, for example, intense mental work is reflected primarily in the state of verbal reflexes, while reflexes to specific stimuli do not yet show any signs of fatigue.
Motor conditioned reflexes to sound and to the word “bell” pronounced by the experimenter were studied in schoolchildren at the beginning and end of the school day. It turned out that the conditioned reflex to the sound of a bell, i.e. carried out on a specific signal, did not detect any changes during the school day. At the same time, the reflex to the word “bell”, i.e. carried out through the second signaling system has undergone significant changes. The latent period of the conditioned reaction lengthened and its magnitude decreased.
The higher sensitivity of the reflexes of the second signaling system to chemical influences was manifested, for example, in the well-known sequence of phenomena of alcohol intoxication. First, the ability to make conscious, reasonable judgments is lost, i.e. The activity of the second signaling system suffers, and only later do reflex disorders of the first signaling system begin.
Localization of the central mechanisms of speech activity and the pairing of the hemispheres. Although the activity of the second signaling system, which generalizes and abstracts complexes of multimodal signals in the form of concepts, covers all the basic mechanisms of the brain (sensory, motor and associative), the performance of various acts of speech function is associated with certain structures of the higher parts of the human brain. These structures, called speech centers were identified in clinical observations and designated by the names of the researchers who described them (Fig. 102). So, Broca's speech motor center the lesion of which causes a disorder of movements involved in oral speech, is located at the base of the inferior frontal gyrus. Wernicke's auditory speech center when damaged, the ability to understand the meaning of heard words is lost, occupies the posterior third of the superior temporal gyrus. Optical speech center, the pathology of which deprives a person of the ability to recognize what is written, located in the angular gyrus.
Rice. 102. Location of some special parts of the verbal signal analyzer in the human cerebral cortex:
1 - speech movements (Broca's center), 2 - articulation of speech, 3 - hand movements when writing, 4 - analysis of speech sounds, 5 - oral verbal signals (Wernicke's center), 6 - written verbal signals, 7 - visual analysis
The predominant localization of “speech centers” in the left hemisphere is associated in the evolution of the human brain with the leading role of his right hand. Thus, along with the paired functioning of the brain hemispheres in many types of its activity, there is also some inequality in relation to the implementation of its higher functions predominantly by the left hemisphere. On this basis, it is assumed that the left hemisphere performs the main functions of the second signaling system. As evidence, they cited observations of patients who were subjected to unilateral therapeutic electric shock.
When the activity of the left hemisphere was suppressed in this way, speech, understanding of words, the ability to read text, and solve logical problems were sharply impaired, but the ability to recognize surrounding objects and understand the meaning of everyday sounds, for example, the bell to open the door, the placement of plates, spoons and forks for preparing dinner, etc., as well as emotional perception of music. When the right hemisphere was subjected to electric shock, the understanding of everyday signal sounds and the emotional perception of music were disrupted, but all manifestations of oral and written speech were preserved.
The opinion about the separateness of the functions of the left and right hemispheres is supported by the results of a study of electroencephalogram reactions to verbal and non-verbal addresses to a person. In the first case, the desynchronization reaction was more pronounced with leads on the left side, in the second - on the right. Studies of ECoG, focal EPs and impulse responses of neurons in cats have shown that during the formation of a conditioned reflex, synchronization of activity first occurs in symmetrical areas of the hemispheres, then its predominance is recorded in the hemisphere contralateral to the side of reinforcement (the first manifestations of the conditioned reflex), and after widespread generalization the activity again concentrated in this hemisphere (strong conditioned reflex).
Human typology. To diagnose human typology, the method of studying conditioned motor reflexes formed on verbal reinforcement is widely used. Typological differences can also be found in changes in the electrical activity of the brain under the influence of intermittent stimulation of increasing intensity (Fig. 103). Here, the strength, balance and mobility of nervous processes are reflected in the most tolerable strength of the stimulus, the excess of which leads to extreme inhibition of electrical activity, in the degree of changes in activity and the speed of development of these changes. Typological features are also revealed when testing ready-made speech-motor reflexes that have developed over the course of life, for example, in the power relations of the conditioned stimulus (loudness of the order) and the reflex (magnitude of the response movement) (Fig. 104).
Rice. 103. Installation for studying changes in the basic electrical activity of the brain under the influence of intermittent stimulation of increasing intensity (according to the method of M.N. Livanov):
1 - metal cabin screen for the test subject, 2 - illuminator with lamp (4) and shutter (3), rotating motor (5), 6 - rheostat for stepwise increase in the intensity of light stimulation, 7 - activation of light stimulation transmitted by a cord (8) key (9) for marking on the electroencephalogram, 10 - conduction of brain potentials
Rice. 104. Individual differences in the course of ready-made speech-motor reflexes when the strength of the verbal signal changes (the magnitude of the movement performed by order is recorded). A B C- reactions in various subjects with greater (A) or less (IN) the strength of nervous processes: I-V- level of order volume from very quiet (I) to deafeningly loud (V)
Typological differences also manifest themselves in everyday behavior. Thus, descriptions of the lives of famous writers gave reason to attribute I.S. Turgenev to the Saguiniki, I.A. Krylov to phlegmatic people, A.S. Pushkin to choleric people, and N.V. Gogol for melancholic people. The presence in a person of two signaling systems that jointly carry out his mental activity has complicated the typology of people. In addition to differences in the general types of the nervous system, there are individual differences in the degree of participation of verbal and concrete signals in the complex analytical and synthetic work of the human brain. They are expressed in the volume of use of the first and second signaling systems and determine special types of higher nervous activity in humans. These differences are only relative, since in every impression, movement of thought and action of a person, both systems participate, with the leading role of the conscious, verbal one.
According to the relationship between the activities of the first and second signaling systems, there are different types of people. Extreme cases of such typological relations I.P. Pavlov called it thoughtful and artistic. The thinking type is characterized by a sharp dominance of the second signaling system over the first and therefore a strong tendency towards abstract thinking. People with a thinking type perceive their surroundings not so much in the form of immediate vivid pictures of life, but in the form of verbal, generalized definitions of it. The artistic type is characterized by a less than usual predominance of the second signaling system over the first and, therefore, a tendency towards concrete thinking. These are people who vividly and vividly perceive their surroundings in images, sounds, colors, touches and smells. A striking manifestation of the artistic type of thinking of I.P. Pavlov considered the work of L. Tolstoy. However, as a rule, people have a mixed (average) type of nervous activity. Later functional studies (O.M. Teplov, 1956) revealed a connection between the state of nervous processes and a person’s personal characteristics; It has also been shown that high sensitivity can compensate for the weakness of the human nervous system and ensure the fullness of its activities. Research in the field of human typology is complicated by the fact that it is necessary to distinguish between general and particular properties of his nervous system (V.D. Nebylitsyn, 1976). Private properties may manifest, for example, different sensory systems of the brain to varying degrees, determining the comparative severity of visual, auditory or other components of perception. General properties characterize the activity of integrative mechanisms of the brain that determine a person’s personality at all levels of its manifestation, carried out mainly by the anterior areas of the cortex in interaction with subcortical structures. Electrophysiological studies have shown that the activity of these particular parts of the brain is characteristic of subjects who showed high levels of motor and mental activity.
Neurophysiological mechanisms of human thinking
The study of how the brain “makes a thought” has only recently become a subject of physiology. Therefore, information about the neurophysiological mechanism of the activity of the second signaling system is still extremely limited. With the current level of knowledge, in order to characterize the features of this activity, it is necessary to study not so much its physiological mechanism as the localization and conditions for the formation of conditional connections that arise in this case. Currently, scattered information has been accumulated about the nervous processes that take place in the structures of the human brain during mental activity. Some results were obtained by clarifying the general issues of how human thinking processes are reflected in the electrical indicators of the activity of the nervous mechanisms of the brain, as well as in the study of the processes of perception, decision-making and concept formation. However, there are still unclear and controversial issues here, starting with the meaning of electrical indicators for determining nervous processes and ending with the problem of human intelligence.
Electrical indicators of the main processes of human brain activity. The human brain, like animals, generates electrical potentials of background rhythms, responds with evoked potentials to afferent stimulation, develops infraslow potentials, and detects the impulses of individual neurons. Based on these indicators, one can to some extent judge the course of nervous processes in the higher parts of the brain and evaluate the comparative participation of its structures in the formation and implementation of acts of higher nervous activity.
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Higher nervous activity (HNA) is a neurophysiological process that occurs in the cortex and immediate subcortex of the brain during various processes associated with conditioned reflexes. These processes include the formation, functioning and extinction of reflexes, not only in humans, but also in animals. The features of higher nervous activity in humans were studied and highlighted by I. P. Pavlov.
Higher nervous activity of man - basics
The basic concepts of higher nervous activity include, first of all, temporary connection and conditioned reflex. It has been proven that, at its core, the activity of each department of the human central nervous system is reflexive and performs signaling functions, which allows the body to respond to conditioned stimuli, which is the physiology of higher nervous activity.
As the doctrine of higher nervous activity says, it all consists of only two processes: excitation and inhibition. The first of them provides the basis for the formation of some temporary connections and conditioned reflexes, but if the conditioned reflex ultimately remains unsupported by the unconditioned one, then it fades away. This extinction is the process of inhibition.
Patterns of higher nervous activity
There are only five laws that form the characteristics of higher nervous activity. These include the following statements:
- when a neutral stimulus is reinforced by an unconditioned one, the formation of new temporary connections invariably occurs;
- if the conditioned stimulus is not reinforced by the unconditioned stimulus, the extinction of temporary connections will inevitably occur;
- in any case, irradiation and concentration of nervous processes are required;
- nervous processes are necessarily connected by mutual induction;
- the formation of dynamic stereotypes, which are complex dynamic systems of reflexes.
Higher nervous activity always obeys these laws, and this is true not only for humans, but also for animals, as Pavlov proved with his famous Pavlov’s dog.
Types of higher nervous activity
Behavior and higher nervous activity are inextricably linked. This is confirmed by the theory about the types of GNI, which are the total sum of the innate and acquired properties of the nervous system. Depending on the course of the processes of excitation and inhibition, Pavlov identified four main types, which differ in their ability to adapt to the situation and resistance to stress.
The study of the types of nervous activity makes it possible to study mental processes more deeply and plays an important role in the development of modern sciences.