The characteristic of the visual sensation corresponding to the intensity of the stimulus is brightness. The intensity of the stimulus is characterized by the threshold of sensation (perception). Theories of color vision

10. Feelings. general characteristics

Reader in general psychology: the subject of knowledge, Reader. Psychology of sensations and perceptions, S.L. Rubinstein Fundamentals of General Psychology

The mental processes by which images of the environment are formed, as well as images of the organism itself and its internal environment, are calledcognitive mental processes. It is cognitive mental processes that provide a person with knowledge about the world around him and about himself.

Feeling this is the simplest cognitive mental process, which consists in reflecting the individual properties of objects and phenomena of the material world, as well as the internal states of the body with the direct impact of stimuli on the corresponding receptors.

The physiological basis of sensation. The sensation arises as a reaction of the nervous system to a particular stimulus and has a reflex character.The physiological basis of sensation is a nervous process that occurs when a stimulus acts on an analyzer adequate to it.Receptor (periphery) -> afferent and efferent nerves -> subcortex and cortex (processing of nerve impulses).The analyzer is the initial and most important part of the entire path of nervous processes, or the reflex arc.(discovered by Sechenov). The reflex ring consists of a receptor, pathways, a central part, and an effector. The interconnection of the elements of the reflex ring provides the basis for the orientation of a complex organism in the surrounding world, the activity of the organism, depending on the conditions of its existence.The sense organ is both a receptor and an effector.

Classification of sensations.

Currently, there are two main types of classification of sensations: genetic and systematic.

Systematic classification of sensations (Sherrington) - according to the classification of receptors:

1. Distant (sight, hearing, smell) and contact (tactile, touch, taste)exteroreceptorslocated on the surface of the body and responding to influences from the external environment; Available environmental conditions

2. interoreceptorsresponding to changes in internal organs. Knowledge of the state of the internal environment

3. proprioreceptorsembedded in muscles and ligaments. - signal movements (kinesthetic sensations), a sense of balance (static sensations). knowledge about the relative position of body parts.

Limitation: not all sensations can be strictly attributed to one or another modality. There are sensations that occupy intermediate positions between traditional modalities. These are intermodal sensations (vibration).

Genetic classification of sensations.

Proposed by the English neurologist H. Head. He discernsepicritical and protopathic sensitivity.Epicritical Sensitivity:younger and more perfect sensitivity, allows you to accurately localize an object in space, it gives objective information about the phenomenon.Protopathic sensitivity:relatively more ancient and primitive, do not give an exact localization neither in external space, nor in the space of the body. They are characterized by constant affective coloring, theyrather reflect subjective statesthan objective processes.The ratio of protapotic and epicritical components in different types of sensitivity is different.Epicritical (desc): sight, hearing, touch, smell, taste. Protopathic vice versa.

Properties of sensations

1. Modality. In the analyzer, only one type of sensation is possible. The eye cannot perceive sound.

2. Quality ( a specific feature that distinguishes it from the rest). For example, the qualities of visual modality include brightness, saturation, and hue. The qualities of auditory sensations: pitch, loudness, timbre.

3. Intensity. The quantitative side of the stimulus, the degree of expression of this quality. The dependence of the intensity of sensation on the physical strength of the stimulus acting on the analyzer is mathematically expressed in the basic law of psychophysics, called

4. Spatial localization- this is a characteristic of sensation that allows you to determine the location of the acting stimulus. Color, light, sound correlates with the source

5. Temporal duration. The duration of the sensation. It is determined by the duration of exposure to the stimulus, its intensity, as well as the functional state of the analyzer. When an irritant is exposed to a sensory organ, sensation does not occur immediately, but after a certain period of time, called the "latent (hidden) period of sensation." When the action of the stimulus ceases, the sensation does not disappear simultaneously with it, but continues for some time in its absence. This effect is called "aftereffect (or inertia) of sensation."

Patterns of sensations.

1. Sensory adaptation.

Adaptation adaptation of sensitivity to a permanent stimulus, manifested in a decrease or increase in thresholds.Example: Adaptation to a long-acting odor, other odors continue to be felt as pungent as before.

Can be distinguished three varieties of this phenomenon.

1. prolonged action of the stimulus - the extinction of sensation. For example, during the day, a person may practically not feel the weight of clothing and its contact with the skin.

2. Adaptation as a dulling of sensation under the influence of a strong stimulus. For example, when a hand is immersed in cold water, the intensity of sensation caused by a temperature stimulus decreases.

1 and 2 - negative adaptation, as a result of which the sensitivity of the analyzers decreases.

3. increased sensitivity under the influence of a weak stimulus. In the visual analyzer, this is dark adaptation, example: visual sensitivity increases when a person enters a darkened space.

It has great biological significance, it helps to capture weak stimuli through the senses and protects the senses from excessive irritation in case of strong influences.

2. Interaction of sensations -change in the sensitivity of one analyzer system under the influence of the activity of another analyzer system.General pattern: weak stimuli in one analyzer system increase the sensitivity of another system, strong lowers it. For example, weak taste sensations (sour) increase visual sensitivity, strong noise reduces the sharpness of central vision, and weak increases. Mutual influences are noted between sound and visual sensations.

3. Sensitization increase sensitivity of the body to something as a result of the interaction of sensations and exercises(for example, hearing develops in children playing music). This is a variant of the interaction of sensations. It differs from adaptation: - Increases only in the direction of severity (adaptation can change in different directions), - Changes only from the well-being of the body, adaptation occurs only under the influence of the environment.

4. Synesthesia excitation by the arising sensations of one modality of sensations of another modality.Sound can be perceived in different colors. Synesthesia is seen in a wide variety of sensations. The most common visual-auditory synesthesia, when, under the influence of sound stimuli, the subject has visual images. There is no overlap between different people in these synesthesias, however, they are quite constant for each individual.

The phenomenon of synesthesia is another evidence of the constant interconnection of the analyzer systems of the human body, the integrity of the sensory reflection of the objective world.

Sensory Isolation and Its Consequences

S.i. - maintenance of the organism in conditions of exclusion from the environment of the maximum number of irritants.

Distinguish 3 types of isolation conditions:

1) absolute nullification of the receipt of irritations (sensory hunger);

2) elimination of stimuli that carry information, but without reducing the strength of the energy impact falling on the receptors;

3) reduction of the sensory environment to a series of simple monotonous and repetitive stimuli.

The 1st condition leads to S. and., the last 2 to perceptual isolation.

The study uses a number of indicators: verbal reports of the subjects, the results of perceptual, mnemonic and intellectual tests, motor activity, cardiac activity, etc.

Researches: in the conditions of S. and. the flow of perceptual processes is disturbed, visual and auditory illusions arise, sociability, clarity of behavior and the ability to think are sharply reduced.During the monotonous hours of the experiment, the subject tries to give meaning to the experimental situation, to make it informative (for example, the subjects try to understand the nature of food, determine the intervals between food servings, count inhalations and exhalations, etc.). They try to compensate for the absence of external stimuli with memories or imagination, but these pictures soon become intrusive, uncontrollable, turn into hallucinations. Feel - the necessary conditions for the functioning of the mind as a whole. A number of researchers note the great importance of the subject's past experience for the outcome of the experiment in S.'s conditions and. The nature of human behavior in the new conditions depends on its internal resources. Obviously, there is a category of people who are easier to manage with their inner world. (T. P. Zinchenko)

The concept of threshold in classical psychophysics

Since sensations depend on external stimuli,the question arose about the nature of this dependence, i.e. about the basic laws to which it obeys. This is the central question of psychophysics. Its foundations were laid by the studies of E. Weber and G. Fechner (“Elements of Psychophysics”).The fundamental question of psychophysics is the question of thresholds.

There are absolute and difference thresholds.

It has been found that not all stimuli cause sensations. It may be so weak that it does not cause any sensation. A known minimum intensity of irritation is needed in order to evoke sensations. The minimum irritation that causes sensation is calledlower absolute limit. IN upper absolute threshold -the maximum intensity possible to experience a given quality

In addition to the thresholds of absolute sensitivity, sensations are also characterized by thresholds of sensitivity to discrimination. The minimum amount of stimulus that causes subtledifferences in feelings, is called difference threshold.

E. WEBER found that a certain ratio between the intensities of two stimuli is required in order for them to give different sensations. This ratio is expressed in the law, established by Weber:the ratio of the additional stimulus to the main one should be a constant value.

Further studies showed that the law is valid only for stimuli of average magnitude: when approaching absolute thresholds, the magnitude of the increase passes to be constant.

The dependence of the intensity of sensation on the physical strength of the stimulus acting on the analyzer is mathematically expressed in the basic law of psychophysics, called"Weber-Fechner law": If the strength of the stimulus increases exponentially, then the intensity of the sensation increases in arithmetic progression.So, a chandelier with 8 lights seems to us as much brighter than a 4-light chandelier as a 4-light chandelier is brighter than a 2-light chandelier. That is, the number of light bulbs should increase several times, so that it seems to us that the increase in brightness is constant.

The problem of measuring sensations. Myself Fechner proposed three psychophysical methods, which entered psychology under the name of basic methods.These methods aim to determine the thresholds.

1. Border method (barely noticeable differences, minimal changes or serial study). The compared stimulus changes in small steps both in increase and decrease. The subject at each measurement of the stimulus must say less than, equal to or more than the standard. As a result of the experiment, the values ​​of the variable stimulus corresponding to the change in response categories are determined. Atdefining an absolute thresholdstandard stimulusnot presentedand the task of the subject is to answer whether there is a stimulus or not.

habituation erroris the tendency to keep the answer "yes" in the descending ranks (with a decrease in stimulus) or the answer "no" in the ascending ranks.Anticipation (or expectation) errorhas the opposite character. The main purpose of alternating ascending and descending rows is to balance out any of the persistent errors, if any.

2. Installation method(mean error, reproduction or trimming method). 2 stimuli, the subject adjusts this stimulus to the standard (it seems to be equal to the standard). Repeat several times, and then calculate the average value and the variability of the test subject's settings. The mean of the trims (sets) is a direct measure of the subjective equality point, and the variability of the trims allowed by the subjects can be used to calculate the difference threshold.When determining the absolute thresholdthe subject repeatedly sets the value of the variable stimulus, which, in his opinion, is the lowest among the detected stimuli. The average of these settings is taken as the absolute threshold.

3. Method of constant stimuli(method of true and false cases or method of frequencies). This method concerns the identification of stimuli lying in the transition zone between perceived and non-perceived.If a stimulus or a difference between stimuli is perceived in 50% of cases, then they respectively indicate the position of the absolute and difference thresholds.In order to get a picture of the entire transition zone, 5-9 different stimuli are usually chosen, ranging from rarely noticed to almost always noticed stimuli. When measuring the absolute threshold, stimuli are also selected that lie on either side of the stimulation threshold or the absolute threshold. There are usually two categories of answers - "yes" and "no". Empty samples of the trap should be included so that the subject does not know about them. The absolute threshold is usually taken as the value of the stimulus at which it is perceived in 50% of cases.

The concept of subsensory range.

It has long been known that far from everything that is perceived by a person and determines his behavior is realized.

Subsensory range- the zone of human sensitivity to imperceptible irritations.

The subsensory area exists in both normal and pathological conditions. Its limits strongly depend on the functional state of a person and range from 5 to 12 dB for hearing.

A complete and accurate characterization of a person's sensory capabilities can only be obtained with the help of involuntary reactions.

Practical importance:in a number of cases, objective reactions represent the only way to measure sensitivity: in young children who have not yet fully mastered speech, with brain pathologies associated with speech impairment, when simulating insensitivity, etc., where it is desirable to measure sensitivity without drawing the subject's attention to irritants.

General concept of sensation.

Sensation is the simplest of cognitive mental processes. The process of sensation arises as a result of the impact on the sense organs of various material factors, which are called stimuli, and the process of this impact itself is irritation. In turn, irritation causes another process - excitation, which passes through centripetal, or afferent, nerves to the cerebral cortex, where sensations arise. Thus, sensation is a sensory reflection of objective reality. The essence of sensation is the reflection of the individual properties of the object. The physiological basis of sensations is the activity of complex complexes of anatomical structures, called by I. P. Pavlov analyzers. Each analyzer consists of three parts: 1) a peripheral section called the receptor (the receptor is the perceiving part of the analyzer, its main function is the transformation of external energy into a nervous process); 2) conducting nerve pathways; 3) cortical sections of the analyzer (they are also called the central sections of the analyzers), in which the processing of nerve impulses coming from the peripheral sections takes place. For the sensation to arise, it is necessary to use all the components of the analyzer. If any part of the analyzer is destroyed, the occurrence of the corresponding sensations becomes impossible. Sensations are not only the source of our knowledge about the world, but also of our feelings and emotions. The simplest form of emotional experience is the so-called sensual, or emotional, tone of sensation, that is, a feeling directly connected with sensation. For example, it is well known that certain colors, sounds, smells can by themselves, regardless of their meaning, memories and thoughts associated with them, cause us a pleasant or unpleasant feeling. Various scientists and philosophers interpreted the relationship of sensations with mental development in different ways. Representatives of the idealistic trend: the true source of conscious activity is not sensations, but the internal state of consciousness, regardless of information from the outside. Idealist philosophers and psychologists tried to prove that sensations not only connect a person with the outside world, but also separate him from the world (Hume, Berkeley-subjective idealism). Müller's theory of the specific energy of the senses (departed from subjective idealism + a bit of materialism "each sense organ has its own internal energy, does not reflect external processes, but receives impulses that excite its own processes"). Helmholtz - the mental images that arise as a result of the impact of objects have nothing to do with objects, they are “symbols” or “signs.” These approaches meant that a person cannot perceive the world around him. The theory of solipsism-man can only know himself. Materialists stood on opposite positions. They considered possible an objective reflection of the world. Man's sensations are a product of historical development and differ from those of animals.

2. Types of sensations.

There are various approaches to the classification of sensations. Since ancient times, there are 5 main types - vision, smell, touch, taste, hearing. B. G. Ananiev has 11 species. Luria divided according to 2 principles: systematic (by modality) and genetic (by complexity). Systematic classification according to Sherrington. Divided into 3 groups: interoceptive (signaling the state of the internal processes of the body, arise due to receptors located on the walls of the stomach and intestines, heart and circulatory system and other internal organs. This is the most ancient and most elementary group of sensations. Receptors that perceive information about the state of internal organs, muscles, etc., are called internal receptors. Interoceptive sensations are among the least conscious and most diffuse forms of sensations and always retain their proximity to emotional states. It should also be noted that interoceptive sensations are quite often called organic.); proprioceptive sensations transmit signals about the position of the body in space and form the afferent basis of human movements, playing a decisive role in their regulation. The described group of sensations includes a sense of balance, or a static sensation, as well as a motor, or kinesthetic, sensation.

Peripheral receptors for proprioceptive sensitivity are found in muscles and joints (tendons, ligaments) and are called Paccini bodies. Peripheral balance receptors are located in the semicircular canals of the inner ear; exteroceptive Feel. They bring information from the outside world to a person and are the main group of sensations that connects a person with the external environment. The whole group of exteroceptive sensations is conventionally divided into two subgroups: contact (caused by the direct impact of the object on the senses. Examples of contact sensations are taste and touch.) and distant sensations reflect the qualities of objects located at some distance from the senses. Such sensations include hearing and sight. It should be noted that the sense of smell, according to many authors, occupies an intermediate position between contact and distant sensations, since formally olfactory sensations occur at a distance from the object, but "at the same time, the molecules that characterize the smell of the object with which the olfactory receptor contacts, undoubtedly belong to this subject.There are intermodal sensations (vibrational sensitivity = tactile + auditory).Head's genetic classification allows us to identify: 1) protopathic (more primitive, affective, less differentiated and localized), which includes organic feelings (hunger, thirst, etc.) 2) epicritical (more subtly differentiating, objectified and rational), which includes the main types of human sensations. Epicritical sensitivity is younger in genetic terms, and it controls protopathic sensitivity. The well-known domestic psychologist B. M. Teplov, considering the types sensations, divided all receptors into two large groups: exteroceptors (external receptors) located on the surface of the body or close to it and accessible to external stimuli, and interoceptors (internal receptors) located deep in tissues, such as muscles, or on surfaces of internal organs. B. M. Teplov considered the group of sensations that we called “proprioceptive sensations” as internal sensations.

Basic properties and characteristics of sensations.

The main properties of sensations include: quality, intensity, duration and spatial localization, absolute and relative thresholds of sensations.

Quality - this is a property that characterizes the basic information displayed by a given sensation, distinguishing it from other types of sensations and varying within this type of sensation. For example, taste sensations provide information about some of the chemical characteristics of an object:

sweet or sour, bitter or salty. The sense of smell also provides us with information about the chemical characteristics of the object, but of a different kind: the smell of flowers, the smell of almonds, the smell of hydrogen sulfide, etc.

It should be borne in mind that very often, when talking about the quality of sensations, they mean the modality of sensations, since it is the modality that reflects the main quality of the corresponding sensation.

Intensity sensation is its quantitative characteristic and depends on the strength of the acting stimulus and the functional state of the receptor, which determines the degree of readiness of the receptor to perform its functions. For example, if you have a runny nose, the intensity of perceived odors may be distorted.

Duration Feelings are a temporal characteristic of the sensation that has arisen. It is also determined by the functional state of the sense organ, but mainly by the time of action of the stimulus and its intensity. It should be noted that sensations have a so-called patent (hidden) period. When a stimulus is applied to the sense organ, the sensation does not occur immediately, but after some time. The latent period of different types of sensations is not the same. For example, for tactile sensations, it is 130 ms, for pain - 370 ms, and for taste - only 50 ms.

The sensation does not arise simultaneously with the beginning of the action of the stimulus and does not disappear simultaneously with the termination of its action. This inertia of sensations is manifested in the so-called aftereffect. A visual sensation, for example, has a certain inertia and does not disappear immediately after the cessation of the action of the stimulus that caused it. The trace from the stimulus remains in the form of a consistent image. Distinguish between positive and negative sequential images. positive serial image corresponds to the initial irritation, consists in maintaining a trace of irritation of the same quality as the current stimulus.

Negative serial image consists in the appearance of a quality of sensation that is opposite to the quality of the irritant. For example, light-darkness, heaviness-lightness, heat-cold, etc. The appearance of negative sequential images is explained by a decrease in the sensitivity of this receptor to a certain effect.

And finally, sensations are characterized spatial localization irritant. The analysis carried out by the receptors gives us information about the localization of the stimulus in space, that is, we can tell where the light comes from, the heat comes from, or which part of the body is affected by the stimulus.

All of the above properties to some extent reflect the qualitative characteristics of sensations. However, the quantitative parameters of the main characteristics of sensations are no less important, in other words, the degree sensitivity. There are two types of sensitivity: absolute sensitivity And sensitivity to difference. By absolute sensitivity is meant the ability to sense weak stimuli, and by difference sensitivity is the ability to sense subtle differences between stimuli. However Not any irritation causes sensation. We do not hear the ticking of the clock in the other room. We do not see stars of the sixth magnitude. In order for a sensation to arise, the strength of the stimulus must have a certain amount. The minimum value of the stimulus at which a sensation first occurs is called the absolute threshold of sensation (it can be upper and lower).Fechner initiated the study of sensitivity thresholds. He believed that a person cannot directly quantify his feelings, so he developed "indirect" methods with which you can quantify the relationship between the magnitude of the stimulus (stimulus) and the intensity of the sensation caused by it. Suppose we are interested in at what minimum value of the sound signal the subject can hear this signal, i.e. we must determine lower absolute threshold volume. Measurement minimum change method is carried out as follows. The subject is instructed to say "yes" if he hears the signal, and "no" if he does not hear. First, the subject is presented with a stimulus that he can clearly hear. Then, with each presentation, the magnitude of the stimulus decreases. This procedure is carried out until the answers of the subject change. The magnitude of the stimulus at which the responses of the subject change corresponds to the threshold for the disappearance of sensation (P 1). At the second stage of the measurement, in the first presentation, the subject is offered a stimulus that he cannot hear in any way. Then, at each step, the magnitude of the stimulus increases until the subject's responses go from "no" to "yes" or "maybe yes". This stimulus value corresponds to threshold of appearance sensations (P 2). S = (P 1 + P 2)/ 2. Absolute sensitivity is numerically equal to a value inversely proportional to the absolute threshold of sensations.The threshold of discrimination has a constant relative value, that is, it is always expressed as a ratio showing what part of the initial value of the stimulus must be added to this stimulus in order to obtain a barely noticeable difference in sensations. This position was called the Bouguer-Weber law.Fechner's law: if the intensity of stimuli increases exponentially, then sensations will increase in arithmetic progression. The intensity of sensations does not increase in proportion to the change in stimuli, but much more slowly. The Bouguer-Weber law (basic psychophysical law) - S \u003d K * LgI + C, (Where S- intensity of sensation; I - the strength of the stimulus; K and C- constants). The American scientist S. Stevens came to the conclusion that the basic psychophysical law is expressed not by a logarithmic, but by a power curve - S = K * R^n.

LECTURE 27

GENERAL CONCEPT OF SENSOR SYSTEMS. VISUAL ANALYZER.

1. The concept of the sense organs, analyzers, sensory systems.

2. Peripheral (receptor), conductive and cortical sections of the analyzers.

3. Classification of receptors.

4.Visual analyzer.

Even Aristotle described five basic senses: sight, hearing, taste, smell and touch. Term « analyzer» (decomposition, dismemberment) was introduced by I.P. Pavlov in 1909 to refer to the totality of formations, the activity of which ensures the decomposition and analysis in the nervous system of stimuli affecting the body. “Analyzers are such devices that decompose the external world into elements and then transform irritation into sensation” (I.P. Pavlov).

Analyzer- a collection of nerve structures, includes:

peripheral, perceiving apparatus (receptors), transforming the energy of irritation into a specific process of excitation;

conductor part, represented by peripheral nerves and conductor centers, it transfers the resulting excitation to the cerebral cortex;

central Part - nerve centers located in the cerebral cortex, analyzing the incoming information and forming an appropriate sensation, after which a certain tactic of the body's behavior is developed.

Absolute threshold of sensation - is the minimum intensity of the stimulus that produces the corresponding feeling. Differential Threshold - this is the minimum difference in intensities that is perceived by the subject. This means that the analyzers are able to quantify the increase in sensation in the direction of its increase or decrease.

Spatial characteristics operating stimuli needed to distinguish between them depend on: 1) specific features of each sensory system and 2) receptive fields. For example, touching the skin of the distal phalanx of the finger of two legs of a compass with a distance of 2 mm between them is felt separately, but in order to feel a separate touch on the skin of the back, the legs of the compass must be moved apart to 60 mm. Two points of the visual field do not merge into one if the light rays reflected by them hit different receptive fields of the retina. The degree of contrast between the active stimulus and its background is also important: well-contrasted objects (for example, black on white) are distinguished more easily than poorly contrasted ones (black on gray). Time response The perception of acting stimuli in humans has an absolute threshold for distinguishing short time intervals, which corresponds to approximately 1/18 second. For example, 18 visual images presented within 1 second merge into continuous movement, 18 touches to the skin in 1 second are perceived as one, and 18 sound vibrations per second are perceived as one very low sound. The resolving power of sensory systems for the perception of stimuli acting at short intervals is limited by the refractory period, during which the system is unable to respond to the presented stimulus.

CLASSIFICATION OF RECEPTORS
The classification of receptors is based on the following principles:

1. The environment in which receptors perceive information (extero-, intero-, proprio- and other receptors).

2. The nature of an adequate stimulus (mechano-, thermo-, photo- and other receptors).

3. The nature of the sensation after contact with the receptors (thermal, cold, pain, etc.).

4. The ability to perceive a stimulus located at a distance from the receptor - distant (olfactory, visual) or in direct contact with it - contact (gustatory, tactile).

5. According to the number of perceived modalities (stimuli), receptors can be monomodal (for example, light) and polymodal (mechanical and thermal).

6. Morphological features and mechanisms of excitation. There are primary sensory (olfactory, tactile) and secondary sensory receptors (vision, hearing, taste).

Stages of activity of the analyzer system

Encoding information in receptors:
Quality coding carried out due to the selective sensitivity of the receptor to an adequate stimulus with a low threshold of excitation, i.e. the receptor "recognizes" its stimulus (eye - light, ear - sound) and due to the existence of chains of modally specific neurons connected by synapses into a certain rigid circuit that transmits information only from its receptive field. Intensity or the strength of the stimulus is encoded by an increase in the frequency of AP, which, in turn, depends on the magnitude of the receptor potential. Spatial coding. Each receptive field has its representation in certain structures of the central nervous system. In addition, the receptive fields overlap, which ensures the reliability of the system and allows weak stimuli to come into contact with the most sensitive receptors and involve less sensitive ones in excitation. Time coding occurs due to a change in the frequency of pulses and the duration of the interpulse intervals.

PHYSIOLOGY OF THE VISUAL ANALYZER

Before reaching the retina, light rays sequentially pass through the cornea, anterior chamber fluid, lens and vitreous body, which together form the optical system of the eye. . At each stage of this path, the light is refracted and as a result, a reduced and inverted image of the observed object appears on the retina, this process is called refraction .
The peculiarity of the topography of rods and cones is that they face their outer photosensitive segments to the layer of pigment cells, i.e. in the direction opposite to the light. Rods are more sensitive to light than cones. So, a rod can excite only one quantum of light, and a cone - more than a hundred quanta. In bright daylight cones that are concentrated in the area of ​​the macula or fovea have the maximum sensitivity. In low light at dusk, the periphery of the retina, where the rods are located, is most sensitive to light. Under the action of a quantum of light in the receptors of the retina, a chain of photochemical reactions occurs, associated with the decay of visual pigments. rhodopsin And iodopsin and their resynthesis in the dark.

Rhodopsin- rod pigment is a high molecular weight compound consisting of retinal - vitamin A aldehyde and protein opsin. When a quantum of light is absorbed by a molecule of rhodopsin 11 - cis-retinal straightens and turns into trans-retinal. This happens within 1-12 sec. The protein part of the molecule becomes colorless and transforms into the state of metarhodopsin II, which interacts with the membrane-bound protein transducin. The latter triggers the exchange reaction of guanosine diphosphate (GDP) for guanosine triphosphate (GTP), which leads to an increase in the light signal. GTP, together with transducin, activates a membrane-bound protein molecule - the phosphodiesterase enzyme, which destroys the cyclic guanosine monophosphate (cGMP) molecule, causing an even greater increase in the light signal. The content of cGMP decreases and the channels for Na + and Ca 2+ are closed, which leads to hyperpolarization photoreceptor membrane and the occurrence receptor potential. The occurrence of hyperpolarization on the photoreceptor membrane distinguishes it from other receptors, such as auditory, vestibular, where excitation is associated with membrane depolarization. Hyperpolarization receptor potential occurs on the membrane of the outer segment, then spreads along the cell to its presynaptic end and leads to a decrease in the release rate of the mediator - glutamate A. In order for the receptor cell to respond to the next light signal, resynthesis of rhodopsin is necessary, which occurs in the dark (dark adaptation) from the cis-isomer of vitamin A, therefore, with a lack of vitamin A in the body, twilight vision deficiency develops (“ night blindness»).

Retinal photoreceptors are connected to the bipolar cell via a synapse. Under the action of light, a decrease in glutamate at the presynaptic terminal of the photoreceptor leads to hyperpolarization of the postsynaptic membrane of the bipolar nerve cell, which is also synaptically connected to ganglion cells. In these synapses, acetylcholine is released, causing depolarization of the postsynaptic membrane of the ganglion cell. An action potential is generated in the axon hillock of this cell. The axons of ganglion cells form the fibers of the optic nerve, through which electrical impulses rush to the brain.

In order to focus light rays reflected from closely spaced objects on the retina, the optical system of the eye must refract them the stronger, the closer the observed object is located. The mechanism by which the eye adjusts to view distant or near objects and in both cases focuses their image on the retina is called accommodation .

The smooth muscles of the ciliary body, controlled by parasympathetic neurons, regulate the tension of the zinn ligament: when the muscles are completely relaxed, the ligament stretches the lens capsule, forcing it to assume the most flattened shape necessary for viewing distant objects.

ACCOMMODATION MECHANISM OF THE EYE

SCHEME OF RAYS TRAVELING THROUGH THE REFRACTIVE MEDIA OF THE EYE

Eye movements. When observing objects moving in the visual field, as well as when a person moves relative to the surrounding world, tracking eye movements , thanks to which the image in the same area of ​​the retina remains unchanged. With visual perception of stationary objects with numerous details of the form, as well as during reading, rapid eye movements designed to fix the most informative details of the object. The images of the eye are not projected onto the retina at all, but onto that area of ​​it that has the maximum resolution. This fovea , which is a small depression with a diameter of about 3 mm in the center of the retina.
When considering any objects, the eyes make about three very fast involuntary and subjectively not felt movements every second, which are called saccades. Due to such movements, the image on the retina regularly shifts, causing irritation of various photoreceptors. The need for saccades is explained by the property of the visual system to respond more strongly to changing stimulation (the appearance or disappearance of a stimulus), while it responds weakly to constant stimulation.

RECEPTION FIELDS OF RETINA CELLS
There are two pathways for signaling from photoreceptors to the ganglion cell:

1. Straight way starts from photoreceptors located in the center of the receptive field and forming a synapse with a bipolar cell which through another synapse acts on the ganglion cell.

2. indirect way originates from the photoreceptors of the periphery of the receptive field, which has a reciprocal relationship with the center due to inhibitory action horizontal And amacrine cells(lateral inhibition).

Approximately half of the ganglion cells are excited by the action of light on the center of the receptive field and inhibited by the action of a light stimulus on the periphery of the receptive field. Such cells are called on-neurons.

D the other half of the ganglion cells are excited by the action of a light stimulus on the periphery of the receptive field and inhibited in response to light stimulation of the center of the receptive field - they are called off neurons.
The receptive fields of ganglion cells of both types in the retina are represented equally, alternating with each other. Both types of cells respond very weakly to uniform diffuse illumination of the entire receptive field, and the strongest stimulus for them is light contrast, i.e., different illumination intensity of the center and periphery. It is the contrasting of image details that provides the necessary information for visual perception as a whole, while the absolute intensity of the light reflected from the observed object is not so important. edge perception, i.e., the perception of the contrast between adjacent surfaces with different illumination is the most informative feature of the image, which determines the extent and positions of different objects.

PATHWAYS OF THE VISUAL ANALYZER
First neuron visual analyzer is a bipolar cell, second neuron- ganglionic. The optic nerve is made up of ganglion cell axons. In the region of the base of the skull, part of the fibers of the optic nerve passes to the opposite side. The remaining fibers, together with the crossed axons of the second optic nerve, form the optic tract, the fibers of which go to the subcortical centers: the lateral geniculate bodies, the superior tubercles of the quadrigemina, the pillow of the optic tubercle, the suprachiasmatic nucleus of the hypothalamus and the nuclei of the oculomotor nerve. These subcortical structures contain the remaining neurons of the visual pathways. The axons of the cells of the lateral geniculate body as part of visual radiation are directed to the occipital lobe, to the central part of the visual analyzer, localized in the cells of the primary visual zone (field 17), which is connected with the secondary visual zones (fields 18 and 19) of the cerebral cortex.

Already at the level of the retina, such complex qualities of the light signal as illumination, color, shape, signal movement are determined. In the subcortical structures of the analyzer, visual information undergoes further, more complex processing, isolation and identification of new qualities of the stimulus due to the presence of more complex receptive fields, columns - vertical clusters of neurons designed to divide information into separate components. At this level, the interaction of both eyes already begins.

Thanks to the neurons of the visual cortex, the main analysis of visual information occurs with the obligatory participation of columns; there are excitatory and inhibitory zones. binocular vision It is provided due to the activity of the cortical end of the visual analyzer; at one point, symmetrical visual fields are presented on the right and left.

color vision - this is the ability of the visual analyzer to respond to changes in the light range between short-wave - violet (wavelength from 400 nm) and long-wave - red (wavelength 700 nm) with the formation of a color sensation. All other colors: blue, yellow, green, orange have intermediate wavelengths. If we mix the rays of all colors, we get white.

There are two theories of color vision. First- three-component theory G. Helmholtz's color perception enjoys the greatest recognition. According to this theory, there are three types of cones in the retina that separately perceive red, green, and blue-violet colors. Various combinations of cone excitation lead to the sensation of intermediate colors. Uniform excitation of all three types of cones gives a sensation of white color. Black color is felt in the event that the cones are not excited. According to second contrast theory E. Hering, based on the existence of three light-sensitive substances in cones (white-black, red-green, yellow-blue), under the influence of light rays alone, these substances disintegrate and a sensation of white, red, yellow colors occurs. Other light rays synthesize these substances and the result is a sensation of black, green and blue colors.

There are three types of color vision disorders:

1. protanopia, or color blindness - blindness to red and green, shades of red and green do not differ, blue-blue rays appear colorless.

2. Deuteranopia- blindness to red and green colors. There is no difference between green and dark red and blue.

3. Tritanopia- a rare anomaly, blue and purple colors do not differ.

4. Achromasia - complete color blindness with damage to the cone apparatus of the retina. All colors are perceived as shades of gray.

GRAPHIC DESCRIPTION OF THE FIELD OF VISION

Visual acuity is considered the degree of distinction between the boundaries and details of the objects under consideration. OZ- that minimum gap between two objects or points at which the eye is still able to see them separately.

A practical measure of OZ is considered to be the reciprocal of the angle of view, that is, the angle formed by the rays coming from the edges of the object under consideration. Visual acuity is determined using alphabetic or various kinds of curly standard tables. When a gaze is fixed on any object, it is perceived central vision. Objects whose images fall not on the central fovea, but on other parts of the retina, are perceived peripheral vision. The space that a person can see with a fixed gaze is called field of view. The field of view is determined using a Forster perimeter device (method of perimetry). There is a separate field of view for the left and right eyes and a total field of view for both eyes. It is not the same in different meridians, downward and outward it is greater than inwards and upwards. The largest field of view for white, the narrowest - for green, yellow, more - for blue and red.

Feeling the depth of space provided with binocular vision . In a person with normal vision, when viewing an object with two eyes, the image falls on symmetrical (identical) points of the retina, and the cortical section of the analyzer unites it into a single whole, giving one image. If the image falls on non-identical, or disparate, points of two retinas, then the image splits. When pressing on the eye from the side, it begins to double in the eyes, since the correspondence of the retinas has been disturbed.

Control questions: 1. What departments make up the analyzer? 2. What types of receptors do you know? 3. Describe the mechanism of eye accommodation? 4. What is visual acuity? 5. What are the pathways of the visual analyzer?

Absolute threshold of sensation - is the minimum intensity of the stimulus that produces the corresponding feeling. Differential Threshold - this is the minimum difference in intensities that is perceived by the subject. This means that the analyzers are able to quantify the increase in sensation in the direction of its increase or decrease.

Spatial characteristics operating stimuli needed to distinguish between them depend on: 1) specific features of each sensory system and 2) receptive fields. For example, touching the skin of the distal phalanx of the finger of two legs of a compass with a distance of 2 mm between them is felt separately, but in order to feel a separate touch on the skin of the back, the legs of the compass must be moved apart to 60 mm. Two points of the visual field do not merge into one if the light rays reflected by them hit different receptive fields of the retina. The degree of contrast between the active stimulus and its background is also important: well-contrasted objects (for example, black on white) are distinguished more easily than poorly contrasted ones (black on gray). Time response The perception of acting stimuli in humans has an absolute threshold for distinguishing short time intervals, which corresponds to approximately 1/18 second. For example, 18 visual images presented within 1 second merge into continuous movement, 18 touches to the skin in 1 second are perceived as one, and 18 sound vibrations per second are perceived as one very low sound. The resolving power of sensory systems for the perception of stimuli acting at short intervals is limited by the refractory period, during which the system is unable to respond to the presented stimulus.

CLASSIFICATION OF RECEPTORS

The classification of receptors is based on the following principles:

1. The environment in which receptors perceive information (extero-, intero-, proprio- and other receptors).

2. The nature of an adequate stimulus (mechano-, thermo-, photo- and other receptors).

3. The nature of the sensation after contact with the receptors (thermal, cold, pain, etc.).

4. The ability to perceive a stimulus located at a distance from the receptor - distant (olfactory, visual) or in direct contact with it - contact (gustatory, tactile).

5. According to the number of perceived modalities (stimuli), receptors can be monomodal (for example, light) and polymodal (mechanical and thermal).

6. Morphological features and mechanisms of excitation. There are primary sensory (olfactory, tactile) and secondary sensory receptors (vision, hearing, taste).

Stages of activity of the analyzer system

Encoding information in receptors

Quality coding carried out due to the selective sensitivity of the receptor to an adequate stimulus with a low threshold of excitation, i.e. the receptor "recognizes" its stimulus (eye - light, ear - sound) and due to the existence of chains of modally specific neurons connected by synapses into a certain rigid circuit that transmits information only from its receptive field. Intensity or the strength of the stimulus is encoded by an increase in the frequency of AP, which, in turn, depends on the magnitude of the receptor potential. Spatial coding. Each receptive field has its representation in certain structures of the central nervous system. In addition, the receptive fields overlap, which ensures the reliability of the system and allows weak stimuli to come into contact with the most sensitive receptors and involve less sensitive ones in excitation. Time coding occurs due to a change in the frequency of pulses and the duration of the interpulse intervals.

PHYSIOLOGY OF THE VISUAL ANALYZER

Before reaching the retina, light rays sequentially pass through the cornea, anterior chamber fluid, lens and vitreous body, which together form the optical system of the eye. . At each stage of this path, the light is refracted and as a result, a reduced and inverted image of the observed object appears on the retina, this process is called refraction .

The peculiarity of the topography of rods and cones is that they face their outer photosensitive segments to the layer of pigment cells, i.e. in the direction opposite to the light. Rods are more sensitive to light than cones. So, a rod can excite only one quantum of light, and a cone - more than a hundred quanta. In bright daylight cones that are concentrated in the area of ​​the macula or fovea have the maximum sensitivity. In low light at dusk, the periphery of the retina, where the rods are located, is most sensitive to light. Under the action of a quantum of light in the receptors of the retina, a chain of photochemical reactions occurs, associated with the decay of visual pigments. rhodopsin And iodopsin and their resynthesis in the dark.

Rhodopsin- rod pigment is a high molecular weight compound consisting of retinal - vitamin A aldehyde and protein opsin. When a quantum of light is absorbed by a molecule of rhodopsin 11 - cis-retinal straightens and turns into trans-retinal. This happens within 1-12 sec. The protein part of the molecule becomes colorless and transforms into the state of metarhodopsin II, which interacts with the membrane-bound protein transducin. The latter triggers the exchange reaction of guanosine diphosphate (GDP) for guanosine triphosphate (GTP), which leads to an increase in the light signal. GTP, together with transducin, activates a membrane-bound protein molecule - the phosphodiesterase enzyme, which destroys the cyclic guanosine monophosphate (cGMP) molecule, causing an even greater increase in the light signal. The content of cGMP decreases and the channels for Na + and Ca 2+ are closed, which leads to hyperpolarization photoreceptor membrane and the occurrence receptor potential. The occurrence of hyperpolarization on the photoreceptor membrane distinguishes it from other receptors, such as auditory, vestibular, where excitation is associated with membrane depolarization. Hyperpolarization receptor potential occurs on the membrane of the outer segment, then spreads along the cell to its presynaptic end and leads to a decrease in the release rate of the mediator - glutamate A. In order for the receptor cell to respond to the next light signal, resynthesis of rhodopsin is necessary, which occurs in the dark (dark adaptation) from the cis-isomer of vitamin A, therefore, with a lack of vitamin A in the body, twilight vision deficiency develops (“ night blindness»).

Retinal photoreceptors are connected to the bipolar cell via a synapse. Under the action of light, a decrease in glutamate at the presynaptic terminal of the photoreceptor leads to hyperpolarization of the postsynaptic membrane of the bipolar nerve cell, which is also synaptically connected to ganglion cells. In these synapses, acetylcholine is released, causing depolarization of the postsynaptic membrane of the ganglion cell. An action potential is generated in the axon hillock of this cell. The axons of ganglion cells form the fibers of the optic nerve, through which electrical impulses rush to the brain.

In order to focus light rays reflected from closely spaced objects on the retina, the optical system of the eye must refract them the stronger, the closer the observed object is located. The mechanism by which the eye adjusts to view distant or near objects and in both cases focuses their image on the retina is called accommodation .

The smooth muscles of the ciliary body, controlled by parasympathetic neurons, regulate the tension of the zinn ligament: when the muscles are completely relaxed, the ligament stretches the lens capsule, forcing it to assume the most flattened shape necessary for viewing distant objects.

ACCOMMODATION MECHANISM OF THE EYE

SCHEME OF RAYS TRAVELING THROUGH THE REFRACTIVE MEDIA OF THE EYE

Eye movements. When observing objects moving in the visual field, as well as when a person moves relative to the surrounding world, tracking eye movements , thanks to which the image in the same area of ​​the retina remains unchanged. With visual perception of stationary objects with numerous details of the form, as well as during reading, rapid eye movements designed to fix the most informative details of the object. The images of the eye are not projected onto the retina at all, but onto that area of ​​it that has the maximum resolution. This fovea , which is a small depression with a diameter of about 3 mm in the center of the retina.

When considering any objects, the eyes make about three very fast involuntary and subjectively not felt movements every second, which are called saccades. Due to such movements, the image on the retina regularly shifts, causing irritation of various photoreceptors. The need for saccades is explained by the property of the visual system to respond more strongly to changing stimulation (the appearance or disappearance of a stimulus), while it responds weakly to constant stimulation.

RECEPTION FIELDS OF RETINA CELLS

There are two pathways for signaling from photoreceptors to the ganglion cell:

1. Straight way starts from photoreceptors located in the center of the receptive field and forming a synapse with a bipolar cell which through another synapse acts on the ganglion cell.

2. indirect way originates from the photoreceptors of the periphery of the receptive field, which has a reciprocal relationship with the center due to inhibitory action horizontal And amacrine cells(lateral inhibition).

Approximately half of the ganglion cells are excited by the action of light on the center of the receptive field and inhibited by the action of a light stimulus on the periphery of the receptive field. Such cells are called on-neurons.

D the other half of the ganglion cells are excited by the action of a light stimulus on the periphery of the receptive field and inhibited in response to light stimulation of the center of the receptive field - they are called off neurons.
The receptive fields of ganglion cells of both types in the retina are represented equally, alternating with each other. Both types of cells respond very weakly to uniform diffuse illumination of the entire receptive field, and the strongest stimulus for them is light contrast, i.e., different illumination intensity of the center and periphery. It is the contrasting of image details that provides the necessary information for visual perception as a whole, while the absolute intensity of the light reflected from the observed object is not so important. edge perception, i.e., the perception of the contrast between adjacent surfaces with different illumination is the most informative feature of the image, which determines the extent and positions of different objects.

Answer
Proprioceptive sensations include sensations of relaxation and muscle contraction. Proprioceptive sensations enable a person to perceive changes in the position of individual parts of the body at rest and during movements. Information coming from proprioceptors allows him to constantly control the posture and accuracy of voluntary movements, dose the strength of muscle contractions when counteracting external resistance, for example, when lifting or moving a load.
2. The numerical characteristic of the average amount of attention of people is equal to ___ units of information.
5–9
1–3
2–4
8–10

Answer
The numerical characteristic of the average amount of attention of people is equal to 5–9 units of information. Attention is the selective focus of perception on a particular object. A numerical characteristic is usually established through an experiment in which a person is presented with a large amount of information for a very short time. The fact that he manages to notice during this time characterizes his amount of attention.
3. A corrective test that allows you to explore the stability of attention was proposed by a French psychologist ...
B. Bourdon
J. Piaget
P. Janet
A. Binet

Answer
A corrective test that allows you to explore the stability of attention was proposed by the French psychologist B. Bourdon. The essence of this test is that the subject is given a form with a set of letters or other characters written in a line (some of them are repeated), and an instruction is received for a certain period of time to look through all the characters in each line, crossing out those that were previously indicated by the experimenter.
4. The theory of memory, which is based on the concept of connections between individual mental phenomena, is ___ theory.
associative
activity
semantic
informational

Answer
The theory of memory, which is based on the concept of connections between individual mental phenomena, is an associative theory. This theory is one of the first psychological theories of memory that has not lost its scientific significance to this day. It arose in the 17th century, was actively developed in the 18th and 19th centuries, and received predominant distribution and recognition in England and Germany. This theory is based on the concept of association developed by G. Ebbinghaus, G. Müller, A. Pilzeker and others.
5. The characteristic of the visual sensation corresponding to the intensity of the stimulus is called ...
saturation
brightness
tone
duration

Answer
The characteristic of the visual sensation corresponding to the intensity of the stimulus is called saturation. Visual sensations arise when electromagnetic waves act on the visual receptor - the retina of the eye. Saturation is the degree to which a given color differs from a gray color that is the same with it in lightness, or, as they say, the degree of its severity. Color saturation depends on the ratio of the number of light rays that characterize the color of a given surface to the total luminous flux reflected by it. The saturation of a color depends on the shape of the light wave.
6. The phenomenon that characterizes the effect of interruptions in activity on memory processes was described by B. V. Zeigarnik as an effect ...
pending action
the edges
novelty
saving

Answer
The phenomenon that characterizes the effect of activity interruptions on memory processes was described by B. V. Zeigarnik as the effect of an unfinished action. B. V. Zeigarnik tested the hypothesis of K. Levin that interrupted tasks, due to the remaining motivational tension, are remembered better than completed ones. It has been found that the number of remembered interrupted tasks is approximately twice the number of remembered completed ones.