Cortical centers involved in the implementation of the speech act. Dominant hemisphere in the formation of speech. Cortical zones of speech. In the cerebral cortex, there are three most important sensory fields for the speech function
The set of nerve formations that provide: the transformation of the energy of irritation into a nerve impulse, the conduction of excitation, its analysis and synthesis, which ensure the occurrence of sensations, is called analyzer.
It should be understood that each analyzer consists of three morphological parts:
1) receptor;
2) conductor;
3) the cortical end of the analyzer, where excitation is perceived as a sensation. Under the cortical end of the analyzer, one should understand the area of the cerebral cortex in which the highest analysis, synthesis and integration of functions take place. According to I.P. Pavlov: "The cortical end of the analyzer is the nucleus and cellular elements scattered around." This definition explains the partial restoration of function when the kernel is damaged. This allows us to speak about the dynamic localization of functions in the cortex of the cerebral hemispheres.
Part of the cortical centers of analyzers is present in the cortex of the hemispheres of not only humans, but also animals. They are specialized in the perception, analysis and synthesis of signals from the external and internal environment, and according to I.P. Pavlov they constitute the first signal system. The cortical centers (nuclei) of the I signaling system include:
1. Centers of general types of sensitivity (cortical end of the analyzer of general sensitivity - temperature, pain, tactile and proprioceptive) - postcentral gyrus, superior parietal lobule.
2.Center for Stereognosy - superior parietal lobule , adjacent to the posterior part of the postcentral gyrus. Stereognosis is a three-dimensional feeling. When the center is affected, the patient ceases to recognize objects by touch, without visual control.
3. hearing center (cortical end of the auditory analyzer) - the medial surface of the superior temporal gyrus (Geshle's gyrus), in the depth of the lateral sulcus.
4. Center of vision (cortical end of the visual analyzer) - on the medial surface of the occipital lobe on both sides of the spur groove.
5. Olfactory Analyzer Center – on the lower surface of the temporal lobe in the region of the hook and hippocampus.
6. The core of the taste center - in the lowest parts of the postcentral gyrus, a seahorse hook.
7. Motor zone - the region of the precentral gyrus of the frontal lobe and the paracentral lobule on the medial surface of the hemisphere.
8. Center of combined head and eye rotation in the opposite direction - the posterior sections of the middle frontal gyrus.
9. Praxia Center - inferior parietal lobule, supramarginal gyrus. Provides the implementation of complex purposeful movements in a certain sequence, learned in the process of life.
10. Account center - inferior parietal lobule, above the angular gyrus.
Rice. 5. Localization of the centers of the 1st signaling system:
1 - the core of the motor analyzer; 2 - the core of the visual analyzer; 3 - the core of the olfactory analyzer; 4 - the core of the taste analyzer.
Speech, and with it consciousness, are among the youngest functions of the human brain. Speech and mental functions are carried out with the participation of the entire cortex. In this regard, the cortical centers of the analyzers that make up the second signaling system are less localized and constitute a set of speech analyzers:
1. Center for Sensitive Speech Analyzer (Wernicke Center) – posterior sections of the superior temporal gyrus (for the right-hander - on the left, and for the left-hander - on the right). The defeat of the center leads to the appearance of sensory aphasia - a violation of the understanding of oral speech.
2. Center for Motor Analyzer of Oral Speech (Broca's Center) – posterior sections of the inferior frontal gyrus (for the right-hander - on the left, for the left-hander - on the right). When it is damaged, motor aphasia develops (impaired oral speech). The patient loses the ability to speak, as his complex speech-motor skills necessary for the pronunciation of syllables, words, and phrases fall apart.
3. Center for sensitive analyzer of written speech (lexia) (the ability to recognize printed characters and the ability to read) - the angular gyrus (right-handed on the left, and left-handed on the right). With its defeat, alexia develops - a disorder of understanding written speech (loss of the ability to read).
4. Center for Motor Analyzer of Written Speech (Graphics) (the ability to write) - the posterior sections of the middle frontal gyrus of the left hemisphere. With the defeat of this center, agraphia (violation of writing) develops.
Rice. 6. Localization of the centers of the 2nd signaling system:
1 - analyzer of general, proprioceptive sensitivity; 2 - the core of the motor speech analyzer; 3 - the core and scattered elements of the auditory analyzer; 4 - scattered elements of the visual analyzer; 5 - the core of the combined turn of the head and eyes; 6 - the core of the analyzer of coordination of movements;
1a – stereognosis analyzer; 2a - the core of speech articulation (Broca's area); 3a - the core and scattered elements of the auditory analyzer of oral speech; 4a - the core of the visual analyzer of written speech; 5a - the core of the motor analyzer of written speech.
human speech centers
There are several speech centers in the brain. Damage to one or more of them can cause speech difficulties. In most people, these centers are located in the left hemisphere of the brain.
Broca's area is located next to the part of the brain that controls the muscles needed for speech. Scientists believe that it coordinates the movements of these muscles.
Wernicke's area helps control the content of speech and also influences the perception of what we see and hear.
A large nerve bundle connects Broca's area and Wernicke and also helps to control the content of speech; allows a person to repeat the sounds and words they hear. Damage to the nerve bundle can deprive a person of the ability to repeat words and phrases.
J. Zeccardi
Speech centers occupy several areas of the cerebral cortex
More than 100 years ago, Brock first discovered that when the lower parts of the third frontal gyrus of the left hemisphere are affected, there is a loss of speech. This is due to the center located next to the sections of the motor area that control the function of the muscles of the face, tongue, palate and pharynx, that is, the muscles involved in articulation. This is the motor center of speech. Extirpation or other lesions of Broca's area lead to impaired speech (aphasia).
Such patients understand speech, but they themselves cannot speak. Speech centers: a - Broca's area; b - Wernicke's area; c - reading center. However, speech impairment in this case is not associated with muscle paralysis, since the muscles are innervated from the precentral gyrus: when this area is stimulated with an electric current, voice reactions are observed on both sides, although sounds are not pronounced (for voice formation, a coordinated reaction of these muscles with exhalation is necessary - see below). A few months after the destruction of Broca's center, speech can be partially restored.
The department that compensates for the remote Broca's center is the area located in the motor zone M-P of the medial parts of the brain. Another speech center is the region of the posterior sections of the first temporal gyrus - the sensory center of Wernicke's speech, located close to the auditory region.
His defeat violates the understanding of speech while maintaining a fairly fluent, albeit somewhat distorted spontaneous speech. This type of pathology refers to sensory aphasia. Removal of the temporal speech zone leads to persistent general aphasia - the inability to understand speech and speak. This confirms the view that this area is the primary center of speech.
In phylogenesis, it was formed earlier than the previous one. Even later, speech centers arose that provide modern man with reading and writing (naturally, speech arose earlier by ear than by sight of the written word).
The center of written speech (reading) is located in the region of the occipital lobe in front of the cortical section of the visual analyzer. The center of writing is located in the frontal lobe above Broca's center, adjacent to the precentral gyrus, where the neurons that control the muscles of the hand are located.
The parietal associative cortex plays an important role in the speech function of the brain. One form of aphasia is amnesia (parietal aphasia), characterized by forgetting individual words (speech memory). Aphasia can occur with atherosclerosis that develops in the parietal cortex.
In this case, it manifests itself gradually and is hardly noticeable to the person himself. In acute development, for example, with a stroke, aphasia can be common. All of these departments of the center of speech in most people are located in the left hemisphere. The left hemispheric location of the center of speech is observed in 95% of right-handers and in 70% of left-handers. In contrast, 15% of lefties have their speech center in the right hemisphere.
SPEECH CENTERS
In the rest of the right-handers and left-handers, speech is controlled from both hemispheres of the brain. Left-handedness and right-handedness are genetically determined traits. The localization of the speech center in the left half of the brain may be evidence that the emergence of speech is closely related to the labor (social) activity of a person: his more responsible (skillful) right hand is innervated precisely from the left hemisphere. In this regard, the retraining in childhood of left-handed people, especially those who have an inborn speech center located on the right, to perform the basic, most subtle types of work with the right hand can lead to a simultaneous movement of the speech center to the left hemisphere (in whole or in part). This can significantly disrupt the speech function of the brain, leading to impoverishment of speech, and often to the development of stuttering. So, in the study of stuttering people, more than half of them found bilateral representation of speech centers.
Perception (analysis and synthesis) of direct, specific signals of objects and phenomena of the surrounding world and signals from the internal environment of the body, coming from visual, auditory and others, constitutes the first signal system that animals and humans have. At the same time, in the process of work and social life, a person develops an “extraordinary increase”, the so-called second signal system associated with verbal signals, speech. This signaling system consists in the perception of words - heard, spoken (aloud or to oneself) and seen (when reading and writing).
in physiology ( NOT in psychology!) it is generally accepted that the ability to understand and then pronounce words develops in a child as a result of certain sounds (words) with visual, tactile and other external objects.
Speech functions
Communicative function speech lies in the fact that speech is considered as a means of communication. Conceptual function speech lies in the fact that speech is a tool of the conceptual, abstract. With the help of speech, not only the analysis and generalization of incoming information is carried out, but also judgments and conclusions are formulated.
Regulatory function speech is expressed in the regulation of activity various bodies and body systems with the help of the word. Verbal ones change the function of internal organs, the intensity of metabolic processes, they also affect the muscular system and on. The word, as a physiologically active factor, influences by its direct content. The action of a word is determined by its semantic meaning.
Forms of speech activity.
Speech associated with the verbal designation of objects can manifest itself in three forms: acoustic, optical and kinesthetic.
Acoustic form of speech presented in the form of sound signals, the perception of which occurs as a result of splitting the speech stream into sections. Such fragmentation ensures the perception of phonemes. At the same time, the integration of individual elements into the speech flow also takes place. The acoustic form of speech is the basis for the implementation of the communicative function of speech.
Optical form of speech provides analysis and integration of individual speech (literal) irritations and implements the symbolic function of speech. When the visual parts of the cerebral cortex are affected, not only the ability to distinguish between letters is impaired, but the symbolic function is often also impaired.
Kinesthetic form of speech manifests itself in the work of the muscular apparatus, articulating organs, with the help of which the realization of the sound expression of speech takes place. muscle tension organs, even in the absence of sound speech expression, is quite high. Physiologically, this is manifested in the work of speech organs in the process of thinking.
Physiological basis of speech
The physiological basis of speech is the second signal system, the conditioned stimuli of which are words in their sound (oral speech) or visual form ( written speech). The sounds and outlines of words, being at first neutral stimuli for an individual, become conditioned speech stimuli in the process of re-combining them with the primary signal stimuli that cause perceptions and sensations of objects and their properties.
As a result, they acquire semantic meaning, become signals of direct stimuli with which they were combined. The temporary neural connections formed in this case are further strengthened by constant verbal reinforcements, become strong and acquire a two-sided character: the sight of an object immediately causes its naming, and, conversely, an audible or visible word immediately causes the representation of the object denoted by this word.
Systems that provide speech can be divided into two groups: peripheral and central. The central ones include certain structures of the brain, and the peripheral ones include the vocal apparatus and organs.
All speech analyzers are laid in both hemispheres, but develop only on one side (for right-handers - on the left, for left-handers - on the right. This zone consists of 3 departments.
Broca's speech motor center- located in the lower part of the frontal gyri (field 44) - this is the motor center of the muscles of the tongue. With the defeat of the motor center of speech, a motor center develops - in this case, a person understands speech, but, alas, he cannot speak.
Wernicke Sensory Center- located in the zone in the posterior parts of the upper temporal (fields 22, 37, 42) - associated with the perception of oral speech. The task of this center is the recognition and storage of oral speech, both one's own and someone else's. With a lesion, sensory aphasia occurs - a person does not perceive oral speech, pronunciation suffers, as the perception of one's own speech is disturbed. A person can speak, express his thoughts orally, but does not understand someone else's speech, and although hearing is preserved, a person does not recognize words. This condition is called sensory auditory aphasia. Such a person often talks a lot (logorrhea), but his speech is incorrect (agrammatism), while there is a replacement of syllables and words (paraphasia).
Breaking the speech circle at any point destroys the speech process. Examples:
1. Deafness blocks Wernicke's center. Trying to restore the speech circle makes you speak loudly. Absolute deafness makes a person dumb (deaf-mute) due to a complete rupture of the speech circle at the level of the Wernicke center. In neurology, this condition is referred to as sensory aphasia.
2. Broca's center is affected in cerebral palsy. The severe form of this disease also drastically disrupts or makes the speech process impossible due to a complete rupture of the speech circle at the level of Broca's center. In neurology, this condition is defined as motor aphasia.
3. The associative center is affected in some neurological diseases, brain injuries. In this case, the ability to compose phrases is impaired. However, these violations are not often observed, because. the associative center is less rigidly structured.
4. Stuttering is a periodic gap in the speech circle (not stable operation of the speech circle).
The human cerebral cortex contains the three most important sensory fields for speech function:
Visual (in the region of the spur groove on the medial surface occipital lobes right and left side);
Auditory (in the zone of the transverse convolutions of Geschl);
Somatosensory (in the posterior central gyrus of each side).
In addition to the primary ones, there are secondary sensory, associative and motor fields located in close proximity to the primary zones. First of all, this is the temporal region of Wernicke, which provides understanding of speech, as well as the most important integrative part of the brain is the frontal lobe, which regulates software speech, concentrated in Broca's area (third frontal gyrus). The interaction of the listed cortical zones is carried out due to:
transcortical associative connections
cortical-thalamic connections
Back in 1861. the French neurosurgeon P. Broca discovered that when the brain is damaged in the region of 2-3 frontal gyri, a person loses the ability to articulate speech or makes incoherent sounds, although he retains the ability to understand what others say. This speech motor area, or Broca's area, is located in the left hemisphere of the brain in right-handed people.
A little later, in 1874, the German neurologist K. Wernicke established that there is also a zone of sensory speech in the superior temporal gyrus. Its defeat leads to the fact that a person hears words, but ceases to understand them, since the connections of words with objects and actions that these words designate are lost. In this case, the patient can repeat words without understanding their meaning. This zone was called Wernicke's zone.
AT motor speech zone there is a selection of movements necessary for the pronunciation of sound combinations, and their sequence is established, i.e. a program is being implemented according to which the organs of articulation should act.
Canadian neurosurgeon Penfield discovered an additional, or upper speech, an area that plays a supporting role. The close relationship of all three speech areas was shown, which act as a single speech mechanism.
When one of the speech zones of the cortex was removed from a patient, the resulting speech impairments became less after a while. This means that the remaining speech areas took over the functions of the remote speech zone. Therefore, speech areas have the principle of reliability. The role of speech areas is not the same. This was shown by the timing and degree of restoration of speech after the removal of one or another speech zone.
It turned out that it is easier and more fully restored when the upper speech zone is removed. When Broca's area is removed, the disturbances are persistent and very significant defects remain, but speech can still be restored. When Wernicke's area is removed, especially if the subcortical structures of the brain are affected, the most severe, often irreversible speech disorders occur.
For the correct course of a speech act, it is necessary to precisely coordinate the work of speech areas. For example, a child wants to call his mother. From Wernicke's area, where the sound image of the word "mother" is stored, the program of what needs to be said is transmitted to Broca's area. Here, a motor program for pronouncing a word is formed, which enters the area of motor projections of the articulatory organs. From the motor projection zone along neural pathways nerve impulses are transmitted to the muscles of the face, lips, larynx, respiratory muscles, and the child pronounces the word "mother". This whole complex process is self-regulating i.e. one link of the act automatically includes the next.
All speech zones are located in the left hemisphere (in right-handed people), however, for normal speech, the coordinated work of both hemispheres of the brain is necessary. In healthy people, during speech, the activity of the symmetrical points of the frontal, temporal, and lower parietal regions in both hemispheres is precisely coordinated, but the course of nervous processes in the left hemisphere is 3-4 thousandths of a second ahead of the course of processes in the right. In patients with stuttering, there is a discrepancy in the activity of symmetrical points up to 44 ms, while the right hemisphere begins to outstrip the left.
The path from the center to the organs of speech is only part of the mechanism of speech. The other part of it is feedback. They go from the muscles to the center and report to the brain about the position of all the muscles involved in the articulation at a given time. This allows the brain to make the necessary adjustments to the work of the articulatory apparatus even before the sound is pronounced. This is a kind of muscular control over the processes of articulation. In addition, there is also auditory control: the word that the child pronounces is compared with the standard stored in the Wernicke zone, the sample of this word. Unlike muscle control, auditory control acts a little later, when the word has already been spoken.
Speech as a function of the brain is deeply asymmetric. The linguistic abilities of a person are determined mainly by the left hemisphere. At the same time, the interconnected speech zones located in the posterior temporal region (Wernicke's area), the inferior frontal gyrus (Broca's area), the premotor area of the left hemisphere and the additional motor cortex, together with the motor cortex of both hemispheres, which controls the coordinated activity of the articulatory apparatus, act as a single speech mechanism.
Ways of implementation of cooperation of various areas of the cerebral cortex in the process of speech functions are as follows. After the information contained in the word is processed in the auditory system or in the "non-auditory" formations of the brain (when reading, for example, in the visual cortex), it must be recognized by meaning. For a person to understand the meaning of speech and develop a speech response program, further processing of the received primary auditory or visual information is necessary. It is carried out in Wernicke's area, located in the temporal region in close proximity to the primary auditory system. It is here that the understanding of the meaning of the incoming signal-word is provided. If written speech is perceived, then the primary visual cortex is turned on first. After that, information about the read word enters the angular gyrus, which connects the visual form of this word with its acoustic counterpart in Wernicke's area. To pronounce a word, it is necessary to activate its representation in Broca's area, located in the third frontal gyrus. After understanding the meaning of speech through the participation of Wernicke's area, the activation of Broca's area is provided by a group of fibers called the arcuate fasciculus. In Broca's area, information coming from Wernicke's area leads to a detailed program of articulation. The implementation of this program is carried out through the activation of the facial projection of the motor cortex, which controls the speech muscles and is connected with Broca's area by short fibers. The path leading to the emergence of a speech reaction in visual perception of written speech is the same as in purely acoustic perception.
With development various techniques Brain research refines and expands knowledge about the brain supply of speech. Thus, it was found that the function of naming objects is performed by different areas of the brain, depending on the ownership of the object. For example, the naming function for general concepts is localized in the posterior left temporal regions, and for specific concepts, in the anterior left temporal regions.
Significant effect on speech functions cerebellum.
Tonal hearing is identical for both hemispheres. The participation of the left hemisphere is necessary for the detection and recognition of articulated speech sounds, and the participation of the right hemisphere is necessary for the recognition of intonations, transport and everyday noises, and musical melodies. The perception and generation of speech sounds is provided by the left hemisphere, and the improvement of signal separation from noise is provided by the right hemisphere. The right hemisphere is not able to implement the command to produce speech, but it provides understanding of spoken language and written words. The understanding of speech, carried out by the right hemisphere, is limited to specific nouns, to a lesser extent, verbs. The right hemisphere provides an understanding of the emotional content of intonations, voice recognition, and participates in the modulation of voice frequencies.
Speech system control
To assess the successful implementation of a particular motor behavioral program, including a speech program, it is necessary to control its implementation both in the process of execution and in terms of the final result. Such an assessment is carried out by the brain thanks to feedback systems. A person has three channels for obtaining information about the successful implementation of the speech process: (1) auditory, (2) proprioceptive, (3) visual.
Speech fidelity, i.e. the correspondence of the acoustic form of the speech signal to its acoustic image is controlled by auditory feedback. It begins in the auditory temporal zone and goes all the way to the hair cells of the cochlea of the inner ear.
The accuracy of speech reproduction is controlled by an assessment from proprioceptive and kinesthetic receptors located in the muscles and joints of the speech-producing organs. Kinesthetic control allows you to prevent an error and make a correction before the sound is pronounced. The control of the final result of the influence of expressive speech on the listener is realized through the visual and auditory channels.
Cortical structures are involved in the organization of speech control. In many cases, these two mechanisms (subcortical and cortical) operate simultaneously and in parallel. The cerebellum is also involved in the control of speech: when it is disturbed, cerebellar dysarthria is observed.
Similar information.
speech centers
areas in the cerebral cortex responsible for various speech functions. Three centers are distinguished: Broca's center, Wernicke's center and field 6 - an area of \u200b\u200bthe secondary motor cortex, localized in the back of the upper frontal
Sound, as well as written speech, is the ability of a sign-symbolic reflection of objects and phenomena of the world around us and ourselves in this world. Speech function is controlled by the higher parts of the human brain - the cerebral cortex, significant areas of sensory and motor areas of which are specialized in the perception, understanding, memorization and reproduction of speech, as well as subcortical formations of the brain that are associated with emotions and memory.
The role of individual areas of the cerebral cortex was first studied in 1870 by German scientists G. Fritsch and E. Gitzig. It has been established that different parts of the cortex are responsible for certain functions. The doctrine of the localization of functions in the cerebral cortex was created. Domestic authors have introduced a lot of new data into this doctrine. So, for example, the Kyiv anatomist V.A. Betz in 1874 proved that each part of the cortex differs in structure from other parts of the brain. This was the beginning of the doctrine of the heterogeneity of the cerebral cortex. I.P. Pavlov considered the cerebral cortex as a continuous perceiving surface, as a set of cortical ends of analyzers. He proved that the cortical end of the analyzer is not some strictly defined zone. In the cerebral cortex, a nucleus and scattered elements are distinguished. The nucleus is the place of concentration of cortical neurons, which make up an exact projection of all the elements of a particular receptor, where the highest analysis, synthesis and integration of functions take place. Scattered elements can be located both along the periphery of the nucleus and at a considerable distance from it. They are more simple analysis and synthesis. The presence of scattered elements during the destruction (damage) of the nucleus partly makes it possible to compensate for the impaired function.
According to the most common classification of K. Brodmann, 52 cell fields are identified in the cortex, each of which has its own serial number (1,2,3.52).
Depending on the functional features in the cortex, motor (motor), sensory (sensitive) and associative zones are distinguished, which make connections between different zones of the cortex. In this paper, we consider one of the most important functional areas of the cortex - the area of speech.
There are several areas in the cortex that are in charge of the function of speech:
1) The motor center of speech (P. Broca's center) is located in the frontal lobe of the left hemisphere - in the "right-handers", in the frontal lobe of the right - in the "left-handers".
2) The sensory center of speech (C. Wernicke's center) is located in the temporal lobe.
3) The zone providing the perception of written (visual) speech is located in the angular gyrus of the inferior parietal lobule.
Speech, as the most important function of the cerebral cortex, is carried out by its various departments, which include the cortical speech zones of the dominant hemisphere. AT human brain there are two main speech zones (Brock's and Wernicke's centers). Both are located in the left hemisphere (Fig. 1).
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