The sensation arises as a reaction nervous system to a particular stimulus and is of a reflex nature. Physiological basis sensation is a nervous process that occurs when a stimulus acts on an analyzer adequate to it.
The analyzer consists of three parts:
1. Peripheral department(receptor), which is a special transformer of external energy into the nervous process;
2. Afferent (centripetal) and efferent (centrifugal) nerves– conductive paths connecting the peripheral part of the analyzer with the central one;
3. Subcortical and cortical sections (brain end) of the analyzer, where the processing of nerve impulses coming from peripheral parts occurs.
In the cortical section of each analyzer there is a nucleus, i.e. central part, where the bulk of the receptor cells is concentrated, and the periphery, consisting of scattered cellular elements, which are located in varying quantities in various areas of the cortex. The receptor cells of the nuclear part of the analyzer are located in the area of the cerebral cortex where the centripetal nerves from the receptor enter. The scattered (peripheral) elements of this analyzer are included in areas adjacent to the cores of other analyzers. This ensures the participation of a significant portion of the cerebral cortex in a separate act of sensation. The analyzer core performs the function of fine analysis and synthesis, for example, it differentiates sounds by height. Scattered elements associated with the function of rough analysis, for example, distinguishing between musical sounds and noise.
Certain cells of the peripheral parts of the analyzer correspond to certain areas of cortical cells. Thus, spatially different points in the cortex represent, for example, different points of the retina; The spatially different arrangement of cells is represented in the cortex and the organ of hearing. The same applies to other senses.
Numerous experiments carried out using artificial stimulation methods now make it possible to quite definitely establish the localization in the cortex of certain types of sensitivity. Thus, the representation of visual sensitivity is concentrated mainly in the occipital lobes of the cerebral cortex. Auditory sensitivity is localized in the middle part of the superior temporal gyrus. Touch-motor sensitivity is represented in the posterior central gyrus, etc.
For sensation to arise, the entire analyzer as a whole must work. The impact of an irritant on the receptor causes irritation. The beginning of this irritation is expressed in the transformation of external energy into a nervous process, which is produced by the receptor. From the receptor, this process reaches the nuclear part of the analyzer along the centripetal nerve. When excitation reaches the cortical cells of the analyzer, the body's response to irritation occurs. We perceive light, sound, taste or other qualities of stimuli.
The analyzer constitutes the initial and most important part of the entire path of nervous processes, or reflex arc. 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 orientation complex organism in the surrounding world, the activity of an organism depending on the conditions of its existence.
In our article we will look at what an analyzer is. Every second a person receives information from environment. He is so used to this that he does not even think about the mechanisms of its receipt, analysis, and formation of a response. It turns out that complex systems are responsible for carrying out this function.
Systems that provide information about changes in the environment and the internal state of the body are called sensory. This term comes from the Latin word "sensus", which means "sensation". The second name for such structures is analyzers. It also reflects the main function.
What is a system that provides perception? various types energy, their transformation into nerve impulses and entry into the corresponding centers of the cerebral cortex.
Despite the fact that a person is constantly faced with a whole range of sensations, only sensory systems five. The sixth sense is often called intuition - the ability to act without logical explanation and foresee the future.
They allow you to perceive about 90% of information about the environment with its help. This is an image of individual objects, their shape, color, size, distance to them, movement and location in space.
Hearing is important for communication and transfer of experience. We perceive various sounds due to air vibrations. Hearing analyzer converts their mechanical energy into which is perceived by the brain.
Capable of accepting solutions chemicals. The sensations it creates are individual. The same can be said about the olfactory sensory. The sense of smell is based on the perception of chemical stimuli from the internal and external environment.
The last analyzer is touch. With its help, a person is able to feel not only the touch itself, but also pain and temperature changes.
Now let's figure out what an analyzer is from an anatomical point of view. Any sensory system consists of three sections: peripheral, conductive and central. The first is represented by receptors. This is the beginning of any analyzer. These sensitive formations perceive various types energy. eyes are irritated by light. The olfactory and taste analyzers contain chemoreceptors. Hair cells inner ear convert mechanical energy oscillatory movements to electric. The tactile system is especially rich in receptors. They perceive vibration, touch, pressure, pain, cold and heat.
The wiring department consists of nerve fibers. Through numerous processes of neurons, impulses are transmitted from the working organs to the cerebral cortex. The latter is the central department of sensory systems. The cortex has a high level of specialization. It distinguishes between motor, olfactory, gustatory, visual, and auditory zones. Depending on the type of analyzer, the neuron delivers nerve impulses through the conductor section to a specific section.
It seems to us that we perceive absolutely all signals from the environment. Scientists say the opposite. If this were true, the brain would wear out much faster. The result is premature aging.
An important property of analyzers is their ability to adapt the level of action of the stimulus. This property is called adaptation.
If sunlight very intense, the pupil of the eye narrows. This is how it manifests itself defensive reaction body. And the lens of the eye is capable of changing its curvature. As a result, we can consider objects that are located at different distances. Such ability visual analyzer called accommodation.
A person is able to perceive sound waves only with a certain oscillation value: 16-20 thousand Hz. It turns out there's a lot we don't hear. Frequencies below 16 Hz are called infrasound. With its help, jellyfish learn about the approaching storm. Ultrasound is a frequency above 20 kHz. Although a person cannot hear it, such vibrations can penetrate deep into the tissue. Using special devices, ultrasound can be used to obtain photographs. internal organs.
Many people have problems with certain sensory systems. The reasons for this can be both congenital and acquired. Moreover, if at least one of the departments is damaged, the entire analyzer stops functioning.
The body does not have internal reserves to restore it. But one system can compensate for another. For example, blind people read using touch. Scientists have found that they hear much better than sighted people.
So, what is a system that ensures the perception of various types of energy from the environment, their transformation, analysis and formation of appropriate sensations or reactions.
What is an analyzer called? What parts does the analyzer consist of? Where are the areas of the cerebral cortex responsible for analyzing visual and auditory information located? Give examples showing the importance of the process of processing information from the senses in the cerebral cortex.
The signal from the receptors passes through several intermediate stages to the cortex cerebral hemispheres brain. A specific area of the cerebral cortex is responsible for processing information coming from each of the senses. Receptors, pathways of the nervous system and a portion of the cerebral cortex together form an analyzer. In the occipital zone lies the visual region of the cerebral cortex, in the temporal zone lies the auditory region, and in the parietal zone lies the region responsible for the perception of touch. Damage to the corresponding areas of the cerebral cortex leads to loss of the ability to analyze signals. Thus, if the occipital region of the cortex is damaged, a person cannot analyze visual information: he is almost no different from a blind person. Scientists called this disorder “central blindness.” The following examples demonstrate the importance of analyzing information from the sense organ in the cerebral cortex. The receptors of the hearing organs in different mammals have a similar structure. The bat's brain analyzes emitted and reflected sounds, and in the dark it accurately determines the location of objects, which a person cannot do. But, thanks to the auditory cortex and speech centers located in the cerebral cortex, in humans the sequence of sounds is compared with a certain semantic meaning. A person easily recognizes familiar melodies by comparing the sound signal with samples of melodies (musical memory).
Sensory disorders
We remember that the analyzer consists of three parts. Each of them may have some deviation from the norm - a disease (for example, inflammation), an organic lesion. But it is clear that the nature of the violations will be different. For example, it’s one thing if there is some kind of inflammation of, say, the middle ear. And it’s a completely different matter when the temporal cortex, where the sound signal is processed, is affected. There are also violations structural organization mental processes, when the temporal fields themselves are intact, but connections in the cerebral cortex are disrupted.
Disturbances of sensations occur both in mental healthy people(usually these are short-term disorders), and in patients (then they are usually long-term and are considered pathologies). There are several types of violations.
Weakness of sensations. This is the indistinctness and weakness of sensations in comparison with the strength of the stimulus. This type of disorder can be observed with insulin hypoglycemia, trauma, and intoxication. It is noted in patients with organic lesions brain, in schizophrenia. In its extreme form, this leads to anesthesia, i.e., to the absence of sensations with any, even the most powerful stimulus. For example, hysterical patients may have insensitive areas of the skin. By the way, this can be suggested to such patients. The Inquisition considered this phenomenon a sign of intercourse with the devil and sentenced such people to death. Oligophrenics have extensive anesthesia, so they tend to inflict various injuries on themselves.
Excessive sensations. At the same time, the light seems too bright, the sound is too loud, the touch is painful. Difficult to tolerate medical procedures. Such conditions occur with meningitis, fever, postoperative period. This also includes discomfort from internal organs; sometimes they turn into hallucinations. IN extreme cases so-called paresthesias occur, i.e. skin sensations, which appear without any external irritation at all. The person feels cold, hot, numb, and goosebumps. These sensations occur with neuritis, circulatory disorders or disorders of the brain or spinal cord.
4.1. Definition: sensation and perception
Let us remember that the initial, or most elementary, level of mental reflection (as well as cognitive activity) - This sensations. One of its main properties is modality, i.e. attachment to one analyzer. Sensation, as a rule, is part of higher-level processes, primarily perception.
From the point of view of old empirical psychological schools, perception is a synthesis of sensations. Within the framework of some idealistic directions (for example, in Gestalt psychology), a seemingly opposite interpretation is proposed: perception is considered as the initial form of cognition. And by sensation is meant the result of the decomposition by consciousness of the results of perception.
Materialistic psychology defines perception as a mental reflection of objects and phenomena of reality in the totality of their properties, in their integrity and with a direct impact on a person. The main distinctive properties of perception are immediacy and multimodality; the result is the construction of a mental image of the perceived object.
This means that sensation and perception have in common their immediacy. However, what distinguishes them is that they have different results: with sensation it is the reaction of the corresponding analyzer, and with perception it is the construction of a holistic image of an object or phenomenon. This happens for two reasons:
1) sensation is always monomodal, and perception is polymodal. For example, you see a table. You see gaps, irregularities - and your tactile analyzers “respond”, and a feeling of roughness arises. You see and “feel” that it is made of wood. And you realize that it is warm (at least compared to a metal table standing somewhere). Thus, although during perception there is a leading analyzer (in the considered example - visual) and we are talking about visual, auditory and other types of perception, other modalities are also involved in the process of receiving information;
2) perception itself enters into mental processes(or is their basis) more high levels- such as cognition, thinking, etc. Therefore, perception is not just a conglomeration of sensations, but the activity of some functional system analyzers. The result of the analyzer system is the construction of a perceptual image. By the way, already in the works of cognitive scientists, the image is interpreted as a model of an object that exists outside of a person.
It should also be noted that the rapid development of psychology at the end of the 20th century led to the fact that the term “perception” began to be used to describe a very wide range of phenomena. Therefore, in works on engineering psychology, for example, they began to distinguish between “perception” and “recognition”. In a number of studies, further differentiation occurs: processes such as “search” and “signal detection”, “signal comparison”, “identification”, etc. were identified.
The study of perception proceeds mainly in two directions: analysis of the characteristics of the image and study of the mechanism of perception itself. Although it must be admitted that not all psychologists adhere to such a classification.
Let us emphasize once again that perception is carried out as a synthesis of different sensations. Nevertheless, it is customary to talk about visual, auditory, tactile and other similar perceptions. In this case, the name of the type of perception includes the name leading analyzer. For example, in visual perception they will be involved in hidden form both motor and tactile analyzers, but the visual one will be the main one.
In addition, we note that in the process of phylogenesis, a number of new complex types of perception arose in humans that were absent in other living beings. Apparently, ancient man there was no sense of perspective yet. And therefore the early rock paintings are planar. These new types of perceptions arise not because new analyzers have appeared, but because there is a complication of the process itself. Such complex types of perception include the perception of time, space, size and shape of surrounding objects, etc.
According to I.P. Pavlov (1909), any analyzer has three sections.
1. Peripheral department analyzer represented by receptors. Its purpose is the perception and primary analysis of changes in the external and internal environments of the body. The perception of stimuli in receptors occurs due to the transformation of the energy of the stimulus into nerve impulses, as well as its amplification due to internal energy metabolic processes. Receptors are characterized by specificity, i.e. the ability to perceive a certain type of stimulus (adequate stimuli), which they developed in the process of evolution. Thus, the receptors of the visual analyzer are adapted to the perception of light, and the auditory receptors are adapted to perceive sound, etc.
2. Conductor section of the analyzer includes afferent (peripheral) and intermediate neurons of the stem and subcortical structures of the central nervous system. It ensures the conduction of excitation from receptors to the cerebral cortex. In the conduction section, partial processing of information occurs, and an important role is played by the interaction of excitations from various receptor apparatuses belonging to different analyzers.
The conduction of excitation through the conduction section is carried out by two afferent pathways. A specific projection path comes from the receptor along strictly designated specific paths with switching at different levels of the central nervous system (at the level of the spinal cord and medulla oblongata, in visual thalamus and in the corresponding projection zone of the cerebral cortex).
Non-specific path includes the reticular formation. At the level of the brain stem, collaterals extend from a specific pathway to the cells of the reticular formation, to which afferent excitations can converge, ensuring the interaction of information from various analyzers. In this case, afferent excitations lose their specific properties (sensory modality) and change the excitability of cortical neurons.
Excitation is carried out slowly through large number synapses. Due to collaterals, the hypothalamus and other parts of the limbic system of the brain, as well as motor centers, are included in the excitation process. All this provides the autonomic, motor and emotional components of sensory reactions.
3. The central, or cortical, section of the analyzer, according to I.P. Pavlov, it consists of two parts: the central part (“core”), represented by specific neurons that process afferent impulses from receptors, and the peripheral part (“scattered elements”) - neurons dispersed throughout the cerebral cortex. The cortical ends of the analyzers are also called “sensory areas,” which are not strictly limited areas, since they overlap each other.
These structural features central department ensure the interaction of various analyzers and the process of compensation for impaired functions. At the cortical level they are carried out higher analysis and synthesis of afferent excitations, ensuring the formation of a complete picture of the environment.
