Anatomy, Physiology, and Pathology of the Organs of Hearing, Vision, and Speech - A. G. Shvetsov 2006

Anatomy, Physiology, and Pathology of Speech
Stages of Speech Formation and Development

In The Development of human speech function, it is essential to distinguish between the development of receptive speech (i.e., its comprehension) and expressive speech (i.e., The ability to speak). Moreover, the capacity to understand speech manifests in an infant as early as the second half of the first year of life, whereas the ability to speak emerges only during the second year. In other words, even before a child begins to speak, they already understand the meaning of words.

Receptive speech is associated with the cortical projections of the visual, auditory, and somatosensory analyzers, as well as the speech comprehension center described by the German psychiatrist and neuropathologist C. Wernicke, located in the posterior third of the superior temporal gyrus (Wernicke's area).

Expressive speech depends crucially on an area of the Cerebral Cortex described by the French anthropologist and surgeon P. Broca. It is located in the posterior third of the inferior frontal gyrus (Broca's area, or the expressive speech center). The functioning of this center is causally determined both by information received from the incoming speech signal and by intrinsic drives and motivation.

The development of expressive speech occurs in parallel with that of receptive speech, and the very process of children acquiring speech as a means of communication During the first years of life goes through several stages.

At the first (preverbal) stage, which covers the first half of the first year of life, the child does not yet understand the speech of others and cannot speak, but the conditions necessary for subsequent language acquisition are gradually established. The child responds not to the word itself—that is, not to the meaning of what is said—since within this complex of stimuli, the word is merely an auditory stimulus. The reaction is triggered by sound intensity, intonation, voice timbre, and a combination of concurrently acting stimuli (such as the sight of a familiar person like the mother, her scent, energy aura, etc.) and typically culminates in a motor act. Naturally, the success of "passing" this stage of speech development depends primarily on the state of the child's Sensory systems, especially auditory and visual. At the Second Stage—The Emergence of speech—the transition from a complete absence of speech to its appearance takes place. This stage serves as a transitional step between two epochs in the child's communication with others: preverbal and verbal. Despite this intermediate position, it is extended over time and usually spans about a year—from the second half of the first year to the second half of the second year of life, and in cases of delayed speech development, it can extend up to a year and a half. The core content of the second stage consists of two events: the comprehension of the speech of surrounding adults emerges, and the first verbalizations appear, marking the period of babbling or syllabic speech.

The Third Stage—the development of speech (language) communication—covers all subsequent time up to the age of 7, during which the child masters language and uses it in increasingly sophisticated and diverse ways to communicate with others. This stage is closely linked to the development and refinement of the second signaling system.

Between the ages of one and a half and 3 years, the child not only masters the pronunciation of words but also significantly expands their vocabulary; by age 5, they concurrently acquire the lexico-grammatical Structure of speech, develop standard speech sound pronunciation, and master the mechanisms of coordination between Respiration, phonation, and articulation, which ensures sufficient fluency of speech utterance. By 5–6 years of age, the child also begins to develop the capacity for phonemic analysis and synthesis, which, under normal development, allows them to transition to a new stage—the acquisition of writing and written language.

This period is the most favorable for language learning (prior to this, infants of all nationalities "coo" in exactly the same way). The child acquires the language spoken by those around them, regardless of their ethnic Background. This is the primary (mother-Tongue) method of language acquisition, and it is based on the first signaling system according to a very simple scheme: sensory image → word.

The secondary method, used mainly for learning foreign languages, is based on knowledge of the "native" language. The scheme of acquiring a new language here is significantly more complex: sensory image → word in the native language → word in the foreign language. Teaching both adults and children this way is far less effective. There are three critical periods in the development of speech function, during which the most intensive development of certain Components of the speech system occurs. Consequently, there is an increased vulnerability of the neural mechanisms of speech activity and a risk of functional disorders, even when exposed to minor exogenous hazards. In these cases, the critical period in speech development acts as a predisposing factor for the emergence of speech disorders, which can either have independent significance or combine with other unfavorable factors—such as genetic predisposition, general physical weakness of the child, Nervous system dysfunction, etc.

The first period—the 1st and 2nd years of life—is when the prerequisites of speech are formed, speech development begins, the foundations of communicative behavior are established, and The Need for communication becomes their driving force. At this age, the most intensive development of cortical speech areas occurs, particularly Broca's area, the critical period for which is between 14 and 18 months of age.

The second period—at 3 years of age—is characterized by the intensive development of coherent speech and the transition from situational to contextual speech, which requires high coordination in CNS functioning (the speech-motor mechanism, perception, attention, memory, etc.). A temporary lack of coordination in the functioning of the CNS, neuroendocrine, and vascular regulation leads to Changes in the child's behavior, such as stubbornness, negativism, etc. All of this accounts for the high vulnerability of the speech system. Stuttering, mutism, or speech development delay may occur. The child may refuse verbal communication, showing a protest reaction to excessive demands from adults. Stuttering, which frequently occurs at this stage, can also be caused by the age-related uneven maturation of individual components of the speech functional system and various mental Functions.

The third period—at 6–7 years of age—marks the beginning of written language development. The load on the child's CNS increases due to mastering the coordination skills of writing and its visual control, which enhances The Importance of the functional state of the tactile and visual analyzers. When excessive demands are placed on the child, "breakdowns" of nervous activity can occur, particularly resulting in stuttering. An analysis of early childhood behavior shows that nothing in their life and behavior dictates an urgent necessity to use speech. Only the presence of an adult who constantly addresses the child with verbal utterances and demands an adequate response, including a verbal one ("What is this?"; "Answer!"; "Name it!"; "Repeat!"), forces them to master speech. Vocal interaction is a form of situational-personal communication, and if a child is not presented with vocal sound as a carrier of communicative information, they do not independently discover the possibilities hidden in this sound for adequate communication. Therefore, if a child, due to special circumstances, finds themselves outside of human society ("Mowgli children") or does not hear adult speech in early childhood (for example, in deaf-mute families), their own speech does not develop, even if their Hearing is intact. It is also known that when the volume of "heard speech" falls below a certain threshold, a state of sensory speech deprivation occurs, which inhibits children's verbal development.

Consequently, only in one-on-one interaction with an adult does the child face a special kind of communicative task—to understand the adult's speech addressed to them and to produce a verbal response. If the adult does not expect a verbal response and does not insist on it, a gap forms between the development levels of passive and active speech, with the latter lagging behind. It has been proven that speech underdevelopment is most commonly observed in children raised outside the family: in orphanages, residential nurseries, and 24-hour preschool institutions. During the period when the child needs communication with close relatives, they are deprived of this opportunity. The communicative factor influences speech development in children across all three stages of its establishment.

Many researchers believe that a negative impact on verbal development is also exerted by speech that is acoustically monotonous, lacking in vivid emotional coloring, and not addressed directly to the child. Thus, the conditions for normal speech development include an intact CNS, normal hearing and Vision, and a sufficient level of active verbal communication between adults and the child.