§2. tactile sensations and their basic qualities. Psychophysiological basis of tactile sensations Sensations - what is it

Taste sensations play an important role in human life. It is taste that determines the qualitative characteristics of food, provides the ability to feel and distinguish Chemical properties substances entering the oral cavity.

Irritants of taste sensations are sweet, salty, sour, bitter. At the same time, taste buds located in different parts of the tongue react differently to the chemical properties of substances.

So, the tip of the tongue perceives predominantly sweet, the back of the tongue is more responsive to bitter, and the left and right edges are sensitive to sour.

Peripheral taste receptors of the tongue are associated with sensory neurons in cranial nerve ganglia. The central sections in the brain stem are represented by the sensory nuclei of these nerves, from which taste signals enter the thalamus and further to the new cerebral cortex. The taste system of sensations is connected by nerve pathways to the nerve center of smell in the brain. That is why when a runny nose appears, the sense of smell worsens and taste sensitivity decreases.

Olfactory sensations carry out psychophysiological functions that allow you to feel and distinguish by smell the chemical compounds in the air. The sense of smell plays an important role in establishing contact with various objects. environment and other people. The olfactory sensory system includes peripheral elements and higher parts of the brain.

It is necessary to pay attention to the fact that tactile sensations are the result of the processing of information received during stimulation of tactile, temperature, pain, muscle and joint receptors. This type sensations is provided by the work of the skin and proprioceptive sensory systems and higher parts of the brain. The ability to touch plays a huge role in the lives of people who have lost sight, hearing or speech.

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Touch - One of the five main types of human senses, consisting in the ability to feel physical touch to objects, to perceive something with receptors located in the skin, muscles, mucous membranes.

Touch is a collective concept. In principle, it would be possible to single out not one, but several independent types of sensations, because they have a different character:

- sensations of touch

- feelings of pressure

- vibration sensations

- sensations of texture,

- feeling of extension.

Tactile sensations are provided by the work of skin receptors of two types:

- nerve endings surrounding the hair follicles,

- capsules consisting of connective tissue cells.

Visual and auditory perception is characterized by a field (volumetric) feature: we perceive the piece of space surrounding us as a whole. That is, we simultaneously see many different objects in front of us, which at the same time can be in some relationship with each other. We perceive at once all the sounds around us that our ear can only perceive. If there is a bright flash before our eyes or some object makes a sharp sound, we will turn our attention to it.

Touch has no such field character. With the help of it, we receive information only about those objects with which we are in physical contact. The only exception is, perhaps, only the sensation of vibration - we can remotely feel with our skin strong vibrations excited by some distant object.

If an object, located just a few centimeters away from us, suddenly changes its shape (for example, its legs parted at the compass) or temperature (for example, a spoon heated up on a burner flame), we will not even notice this if we use only the means of touch . Touch, of course, gives us a lot for life. However, for the cognition of objective reality, as noted by S. L. Rubinshtein, touch plays only a subordinate role. He also noted that what is real for the cognition of reality is not a passive touch of something on a person’s skin, but an active touch, a person’s feeling of the objects surrounding him, associated with the impact on them. With touch, the knowledge of the material world is accomplished in the process of movement, turning into a consciously purposeful action of feeling, effective knowledge of the object.

Touch includes sensations of touch and pressure in unity with kinesthetic, muscular-articular sensations. Touch is both extero- and proprioceptive sensitivity, interaction and unity of one and the other. Proprioceptive components of touch come from receptors located in muscles, ligaments, articular bags (pachinian bodies, muscle spindles). When moving, these receptors are irritated by a change in voltage.

A person has a very specific organ of touch - the hand. The hand, even in a passive state, is capable of giving us a lot of tactile information, but, of course, the main cognitive value lies precisely in the moving hand. The hand is both an organ of human labor and, at the same time, an organ of cognition of objective reality.

The hand differs from other parts of the body in that:

– sensitivity to touch and pressure on the palm and fingertips is many times greater than on the back or shoulder,

- being an organ formed in labor and adapted to influence objects of objective reality, the hand is capable of active touch, and not only of the reception of passive touch,

- has an extensive projection in the cerebral cortex.

S. L. Rubinshtein notes that the hand determines the following basic properties of the material body with which it comes into contact:

- hardness,

- elasticity,

- impenetrability.

The difference between hard and soft, for example, is made by the resistance that the hand encounters when it comes into contact with the body, which is reflected in the degree of pressure on each other of the articular surfaces. Tactile sensations (touch, pressure, together with muscular-articular, kinesthetic sensations), combined with a variety of skin sensitivity data, reflect many other properties through which we recognize objects of the world around us:

- the interaction of sensations of pressure and temperature gives us sensations of humidity,

- the combination of moisture with some malleability or permeability allows us to recognize liquid bodies in contrast to solid ones,

- the interaction of sensations of deep pressure is characteristic of the sensation of soft,

– in interaction with the thermal sensation of cold, they give rise to a sensation of stickiness,

- We recognize the roughness and smoothness of the surface as a result of vibrations that are obtained when the hand moves over the surface, and differences in pressure on adjacent areas of the skin.

The hand from early childhood, already in a baby, is one of the most important organs of cognition of the environment. The baby reaches out with his little hands to all objects that attract his attention. preschoolers and often junior schoolchildren also, at the first acquaintance with the object, they grab it with their hands, actively turn it around, move it, and raise it. The same moments of effective familiarization in the process of active cognition of the subject take place in the experimental situation as well.

From infancy, a person's sense of touch functions in close conjunction with vision and under its control. When a person, unfortunately, is deprived of sight as a result of blindness, the sense of touch also develops, it tends to compensate for the lack of vision, but it takes much more time to perceive space and individual objects, often the picture remains incomplete. It is difficult, for example, for a blind person to know the shape of a tree or the size of a house. However, with due diligence, some objects can be perceived by the blind and deaf-blind with amazing accuracy. This is confirmed by the sculptures of the works of blind masters.

Palpation is involved in the perception of speech of the deaf-blind-mute. "Listening" to speech by the deaf-blind-mute according to the method of "reading from the voice" consists in the fact that the deaf-blind person puts his hand with the back of his hand to the neck of the speaker in the region of the vocal apparatus and catches the speech by means of tactile-vibratory perception.

In all people, tactile sensations can cause certain emotions. Usually this connection is conditioned reflex in nature (that is, it is the result of experience). The interesting thing is that people vary quite a lot in the degree of "emotional touch". For many people, tactile sensations do not cause any noticeable emotions at all. Many, on the contrary, are too “fixated” on their tactile sensations.

Touch, or the perception of mechanical stimuli by the skin, is differentiated into touch, pressure (pressure) and vibration. According to the nature of the irritation, touch can be defined as an unstable deformation, pressure - static, vibration - a pulsating deformation. In organoleptics, the most important is the sensation of touch.

Tactile, or tactile (from the Latin tactilus - tactile), sensations allow you to determine the consistency, structure, temperature of the product, the degree of grinding and some other physical properties.

Sensitive receptors that respond to touch, deep touch, temperature, are abundantly located in the oral cavity (mainly on the tip of the tongue and gums), on the fingertips, and palms. About 500 thousand receptors are located on the surface of the skin and in the mucous membrane of the oral cavity and nose. The tip of the tongue, lips and fingertips are most sensitive to pressure and touch. By touch, with the help of fingers, they control the degree of grinding of flour, the state of the surface, the elasticity and wilting of fresh fruits and vegetables, the elasticity of meat and fish tissues, and the quality of the dough.

The receptors of the oral cavity can touch, as well as feel the temperature, pain. Impressive tactile receptors make it possible to detect foreign inclusions in the product, a deviation from the normal level of such indicators as density, degree of grinding, juiciness, fragility, etc.

The ability to touch depends on external factors and the individual characteristics of the tasters. At negative temperatures, the tactile susceptibility of the receptors decreases. With age, a person's sense of touch usually weakens, but to a lesser extent compared to other senses.

The perceiving organs of touch are located at different depths of the human skin, as seen in Fig. 10.

With the help of deep touch, you can evaluate the area and shape of products, the elasticity of the tissues of meat and fish products, and a number of other indicators. The touch receptors are most densely located on the palms, and it has been established that the threshold for touch perception is different for both hands: it is much higher for the left hand. In addition to the touch threshold indicator, the sensitivity to touch is also evaluated by the "distance threshold" value, i.e. the minimum distance between two objects touching the skin at the same time, at which there is a feeling that exactly two objects are touching the skin at the moment.

Research has established that the fingertips perceive pressure of - 0.028 - 0.170 g / mm 2.

When perceiving the sensation of touch, the phenomena of adaptation, fatigue, induction of the organ of touch are observed. For example, if you press on the surface of the skin for a long time, then the person stops feeling pressure, i.e. adaptation of the sensory analyzer occurs.

If the stimulus acts on the organ of touch continuously, then "fatigue" of the receptor appears, and the signal does not reach the brain. However, it has been found that neighboring receptors become more sensitive in this case. This phenomenon is called the induction of touch.

Touch by palpation (fingertips) is used in testing the quality of products, for example, when assessing the degree of grinding of flour, the evenness or roughness of the surface of vegetables, fruits, other plant products, the uniformity of particles of powdered products, such as cocoa. The organs of deep touch when controlling the quality of products evaluate the hardness (degree of ripeness of fruits), density and elasticity of fish products (salted fish, balyk products, cold smoked products), and many meat products. The lack of elasticity in the tissues of chilled fish or meat can indicate the level of quality, as well as be a sign of staleness.

Recently, in addition to the five well-known sensations (sight, smell, taste, touch and hearing), a sixth type, called kinesthesis, has been added. It is the pressure and shift sensitivity of certain receptors in the muscles and joints. Kinesthetic sensation is used in evaluation activities by specialists in baking and cheese making.

The organs of touch in the oral cavity perceive fibrousness, crumbling, tenderness, stickiness, juiciness, density, granularity and other indicators.

Hearing sensations play a secondary role in sensory testing of products. They can enhance the sense of touch, as well as taste and smell, for example, when evaluating pickles and canned cucumbers, sauerkraut, fresh apples, crackers and lamb products, and some other products.

The organ of hearing (ear) perceives sounds, which are air vibrations with a frequency of 16,000 to 20,000 vibrations per second. During the propagation of sound waves, the pitch and intensity of the sound are distinguished. The pitch of the sound depends on the frequency of vibrations, and the intensity depends on their amplitude. In the process of organoleptic testing of products, while biting through the samples, the taster simultaneously with the sensation of touch perceives, as a rule, various rustles, but not sounds.

While eating, a person is interested not only in the quantity of food, but also in its taste. Taste is a psychophysiological function that provides the ability to sense and distinguish the chemical properties of substances entering the oral cavity. Irritants of taste sensations - sweet, salty, sour, bitter. Taste receptors (chemoreceptors) are located on the surface of the tongue (except for its lower part), palate, tonsils and back of the throat.

The relative concentration of receptors in these areas is not the same. So, the tip of the tongue reacts mainly to sweet, the back of the tongue is more sensitive to bitter, and the left and right edges are more sensitive to sour.

Peripheral taste receptors of the tongue are associated with sensory neurons in cranial nerve ganglia. The central sections in the brain stem are represented by the sensitive nuclei of these nerves, and which taste signals enter the thalamus and then to the new cerebral cortex.

The gustatory system of sensations is nerve pathways (connected to the nerve center of smell in the brain. That is why there is a connection: with a runny nose, smell worsens and taste sensitivity decreases.

The sense of smell is involved in establishing contact with various environmental objects and with other people. The sense of smell is a psychophysiological function that allows you to feel and distinguish by smell the chemical compounds that are in the air. The olfactory sensory system includes peripheral elements and higher parts of the brain.

Irritants of olfactory sensations are odorous substances contained in the air. Olfactory receptors, located in the upper part of the nasal cavity, perceive the odors of substances. Electrical signals are also formed here, which, through the olfactory nerve, enter the olfactory bulb - a part of the brain in the frontal lobe of the hemisphere.

There is no strict classification of odors. The following smells are usually distinguished: floral (rose, lily of the valley, etc.), burnt (tobacco, roasted coffee, etc.), aromatic (camphor, pepper), musky (musk, amber), onion (onion, iodine), goat (valerian, sweat), narcotic (hashish, opium), nauseating (faeces, rotten meat products). In this regard, sensations are also identified with the smell of the odorous substances listed above.

In terms of olfactory and gustatory sensations, people differ little, although there are people with increased sensitivity to smells and tastes of products (tasters, for example). Olfactory and gustatory sensations are influenced by other types of sensations. For example, the feeling of hunger sharpens the sensitivity to sweet and sour, and the smell of menthol causes a feeling of coolness.

It has been established that each person has his own, characteristic only for him, body odor. This fact, along with fingerprinting, is used by law enforcement agencies to identify individuals. And psychologists dealing with family and marriage problems recommend that a couple entering into marriage test themselves for smell compatibility.

A person learns the surrounding objects by touching them. At the same time, he receives information about their shape, surface, hardness, temperature. In such cases, it is said that a person cognizes the world through touch. Touch is a psychophysiological function that allows you to feel and distinguish the shape, size, nature of the surface and temperature of environmental objects. Naturally, these parameters can be determined only on the basis of a combination of movement and direct touch.

Tactile sensations arise on the basis of the processing of information received during irritation of temperature, tactile, pain, muscle and joint receptors. Thus, tactile sensations are provided by the work of the skin and proprioceptive sensory systems and, of course, the Higher parts of the brain.

The ability of a person to tactile sensations is widely used in restoring sight, hearing and speech to people who have lost them.

Touch (kinesthetics, tactile sense) is one of the five main types of senses that a person is capable of, which consists in the ability to feel touch, to perceive something with receptors located in the skin, muscles, mucous membranes. The sensations caused by touch, pressure, vibration, the action of texture and extension have a different character. They are caused by the work of two types of skin receptors: nerve endings surrounding the hair follicles, and capsules consisting of connective tissue cells.

Sensation is the simplest mental process, which is a mental reflection of individual properties and conditions of the external environment, arising from a direct impact on the sense organs, a differentiated perception by the subject of internal or external stimuli and stimuli with the participation of the nervous system. In psychology, sensations are considered the first stage (in fact, they are not included there) of a series of biochemical and neurological processes, which begins with the impact of the external (environment) environment on the receptors of the sensory organ (that is, the organ of sensation) and then leads to perception, or perception (recognition ).

According to the nature of irritation, touch is an unstable deformation, pressure is static, vibration is a pulsating deformation. In organoleptics, the most important is the sensation of touch.

Skin sensitivity includes sensations of touch, pain, warmth, and cold.

The term "touch" is used in two different senses: as a synonym for skin sensitivity; as haptic sensitivity, which includes the sensation of touch and kinesthetic sensations. Haptic sensitivity is manifested in the process of touching an object with a hand.

If the object rests on the hand, then this is a passive touch. If the subject actively touches the object (a combination of touch and kinesthetics), we can talk about active touch.

The main qualities reflected in the tactile sensations are:

1. touch;

2. pressure;

3. quality of the surface of the acting body (“texture”), i.e. smoothness or roughness of the material of the object;

4. length - a reflection of the area of the mechanical stimulus;

5. a reflection of the density of the object or a feeling of heaviness.

The interaction of tactile and kinesthetic sensations provides a reflection of the main mechanical properties of the object - hardness, elasticity, impenetrability.

When the sense of touch of any part of the surface of the body is disturbed, a person ceases to feel this part as his own, it seems alien to him.

Different parts of the human skin are characterized by different absolute sensitivity to touch and pressure. Determine the threshold tactile sensations using a set of Frey hairs. The diameter of each hair was measured using a microscope. The threshold of tactile sensations is measured on the basis of the diameter of the hair at its pressure per 1 sq. mm skin.

The sensitivity of the tactile receptors of the skin depends on the pressure changes that occur when the object and the skin are rubbed. In the absence of pressure changes or their insignificance, the tactile analyzer quickly adapts to the stimulus. We feel the ring on the finger when we take it off or put it on, i.e. in the presence of friction or pressure changes.

If the stimulus acts on the sense organ continuously, then the “fatigue” of the receptor appears, while the signal does not reach the brain. However, it has been found that neighboring receptors become more sensitive in this case. This phenomenon is called the induction of touch.

Tactile sensitivity is most developed on the parts of the body most distant from the center of the body: hands, fingertips, tongue, toes.

Sensitive receptors that respond to touch, deep touch, temperature, are abundantly located in the oral cavity, on the fingertips, palms. The tip of the tongue, lips and fingertips are most sensitive to pressure and touch. Finger touch (palpation) controls the degree of flour grinding, surface condition, elasticity and wilting of fresh fruits and vegetables, elasticity of meat and fish tissues, and dough quality.

It was found that the level of perception of touch for both hands is different: it is much higher for the left hand. In addition to the indicator of the level of touch, sensitivity to touch is also estimated by the “distance threshold” value, i.e. the minimum distance between two objects touching the skin at the same time, at which there is a feeling that exactly 2 objects are touching the skin at the moment.

The signals coming from the internal organs are less noticeable, in most cases, with the exception of painful ones, they are not recognized, but they are also perceived and processed by the central nervous system. The corresponding sensations are called interoceptive. Information from the internal organs continuously flows into the brain, informing it about the states of the internal environment, such as the presence of biologically useful or harmful substances in it, body temperature, the chemical composition of the fluids present in it, pressure, and many others. In addition, a person has several specific types of sensations that carry information about time, acceleration, vibration, and some other relatively rare occurrences having a certain vital importance. According to modern data, the human brain is the most complex, self-learning analog computing machine that operates according to genotypically determined and acquired programs in vivo, which are continuously improved under the influence of incoming information. Processing this information, the human brain makes decisions, gives commands and controls their implementation.

Sensations are usually generated by electromagnetic waves that are within a significant range - from short cosmic rays to radio waves with a wavelength measured many kilometers. The wavelength as a quantitative characteristic of electromagnetic energy is subjectively presented to a person in the form of qualitatively diverse sensations. For example, those electromagnetic waves that the visual system reflects range from 380 to 780 billionths of a meter and, taken together, occupy a very limited part of the electromagnetic spectrum. Waves that are within this range and differ in length, in turn, give rise to sensations of different colors.

The following types of sensations are distinguished: visual, auditory, skin, olfactory, gustatory, kinesthetic, static, vibrational, organic and pain.

The intensity of sensations is their quantitative characteristic. Feelings of the same quality are always stronger or weaker. The intensity is determined by the strength of the stimulus. The quantitative and qualitative characteristics of the stimulus are closely related. Each sensation is also characterized by duration, which is its temporal characteristic. The duration of the sensation depends on the duration of the stimulus.

General patterns of sensations: sensitivity thresholds, adaptation, interaction, sensitization, contrast, synesthesia.

The stimulus, acting on the analyzer, does not always cause a feeling. The touch of the fluff on the body cannot be felt. If a very strong stimulus is acting, there may come a moment when the sensation ceases to arise. We do not hear sounds with a frequency of more than 20 thousand hertz. Too much irritant can cause pain. Consequently, sensations arise under the action of a stimulus of a certain intensity. Psychological characteristics the relationship between the intensity of sensations and the strength of the stimulus expresses the concept of the threshold of sensitivity. There are the following thresholds of sensitivity: lower absolute, upper absolute and threshold of sensitivity to distinctions. The smallest force of the stimulus, which, acting on the analyzer, causes a barely noticeable sensation, is called the lower absolute threshold of sensitivity. The lower threshold characterizes the sensitivity of the analyzer.

The ability of a person to tactile sensations is widely used in restoring sight, hearing and speech to people who have lost them.

There is a relationship between absolute sensitivity and threshold value: the lower the threshold, the higher the sensitivity, and vice versa. Our analyzers are very sensitive organs. They are excited by a very small force of the energy of the stimuli corresponding to them. This applies primarily to hearing, vision and smell. The threshold of one human olfactory cell for the corresponding aromatic substances does not exceed 8 molecules. And it takes at least 25,000 times more molecules to produce a taste sensation than it does to create an olfactory sensation. The very strength of the stimulus at which a sensation of this type still exists is called the upper absolute threshold of sensitivity. Sensitivity thresholds are individual for each person.

The sensitivity of analyzers, determined by the magnitude of absolute thresholds, is not constant and changes under the influence of physiological and psychological conditions, among which the phenomenon of adaptation occupies a special place.

Adaptation, or adaptation, is a change in sensitivity under the influence of a constantly acting stimulus, which manifests itself in a decrease or increase in thresholds. In life, the phenomenon of adaptation is well known to everyone. When a person enters a river, the water at first seems cold. But then the feeling of cold disappears. This can be observed in all types of sensitivity, except for pain. The degree of adaptation of various analyzer systems is not the same: high adaptability is characteristic of olfactory sensations, tactile (we do not notice the pressure of clothes on the body); it is less characteristic of auditory sensations. The phenomenon of adaptation in olfactory sensations is well known: a person quickly gets used to an odorous stimulus and completely ceases to feel it. Adaptation to various aromatic substances occurs at different speeds. A slight adaptation is characteristic of pain sensations. Pain signals the destruction of the body, so adaptation to pain can lead to the death of the body.

If adaptation to darkness is associated with increased sensitivity, then light adaptation is associated with a decrease in light sensitivity.

The interaction of sensations is a change in the sensitivity of one analyzer system under the influence of the activity of another system.

The general pattern of the interaction of sensations is as follows: weak stimuli of one analyzer system increase the sensitivity of another system, strong ones decrease it. For example, weak taste sensations (sour) increase visual sensitivity. Weak sound stimuli increase the color sensitivity of the visual analyzer. At the same time, there is a sharp deterioration in the various sensitivity of the eye due to the strong noise of an aircraft engine.

So, all our analyzer systems are capable of influencing each other to a greater or lesser extent.

An increase in sensitivity as a result of the interaction of analyzers, as well as systematic exercises, is called sensitization. The possibilities for training the sense organs and their improvement are very great. There are two areas that determine the increase in the sensitivity of the senses:

Sensitization due to the need to compensate for sensory defects (blindness, deafness);

sensitization due to specific requirements activities.

All this is proof that our sensations develop under the influence of the conditions of life and the requirements of practical activity.

The contrast of sensations is a change in the intensity and quality of sensations under the influence of a preliminary or accompanying stimulus.

In the case of the simultaneous action of two stimuli, a simultaneous contrast occurs. Such a contrast can be traced in visual sensations.

The same figure appears lighter on a black background, darker on a white one. A green object on a red background seems more saturated. The phenomenon of consistent contrast is also well known. After a cold, a weak warm stimulus seems hot. The sensation of sour increases the sensitivity to sweet. The phenomena of consistent contrast or consistent image in visual sensations have been studied in sufficient detail. If you fix a bright spot with your eye for 20-40 seconds, and then close your eyes or look at a low-light surface, then within a few seconds you can feel a fairly clear dark spot. This will be a consistent visual image.

The physiological mechanism for the emergence of a sequential image is associated with the phenomenon of the aftereffect of the stimulus on the nervous system. Termination of the action of the stimulus does not cause an instant cessation of the process of irritation of the receptors and excitation in the cortical parts of the analyzer.

The interaction of sensations is also manifested in such a phenomenon as synesthesia. Synesthesia is the occurrence under the influence of irritation of one analyzer of sensations characteristic of another analyzer.