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Typical and atypical language development in early childhood

Relationship of autism, language disorders, and mental retardation. Mental Retardation Mental retardation refers to a wide range of nonprogressive brain dysfunction syndromes that affect the development of both intellectual and social-adaptive abilities.

In 1992, the American Association of Mental Retardation changed the definition of mental retardation by shifting the emphasis from the severity of cognitive impairment to the intensity level intermittent, limited, extensive, and pervasive of support services required by the individual for daily functioning.

This change in classification reflects the capacities and interactions of the affected individual with his or her environment.

Preschool Children Who Have Atypical Patterns of Development

Nearly twice as many males as females are affected. The prevalence of mild retardation varies inversely with socioeconomic status of the family, but moderate-to-severe retardation occurs with equal frequency across all social classes.

In the majority of cases, the child progresses sequentially through the typical stages but develops at a slower pace than normal. The age at which parents first become concerned about their child correlates with the degree of retardation.

Mild-to-moderate retardation is identified later when delays in language and play behaviors become more noticeable. Children who are mentally retarded exhibit a range of deficits in language and communication ability compared with their normally developing peers.

However, the language development of mildly affected children resembles that of younger age children matched for mental age, suggesting that mental retardation does not include a linguistic deficit above and beyond that attributed to the cognitive deficit.

Mental retardation per se does not have a primary typical and atypical language development in early childhood on interest in social interaction. Although the most severely affected infants may be slow to learn typical social games, they are otherwise responsive and affectionate toward others. For example, older preschoolers who have cognitive delays are more likely than their normally developing peers to respond to frustration with tantrums or physically aggressive behaviors eg, biting, grabbing objects from peers than by expressing themselves verbally or seeking assistance from adults.

Even minor changes in routines or environment may lead to adverse behavioral reactions and stereotypies, such as self-injury, aggression, or rocking.


Although often an isolated disability, mental retardation commonly is associated with other developmental disorders, including cerebral palsy, epilepsy, vision and hearing impairments, communication disorders, pervasive developmental disorders, and attention deficit disorder.

Other prenatal causes include abnormalities of brain development eg, cerebral dysgenesis and congenital hydrocephalus and central nervous system insults from toxins eg, fetal alcohol syndrometeratogens eg, chemotherapy, anticonvulsantsinfections cytomegalovirus, Toxoplasmaor maternal illness. Language Disorders The terms speech and language disorder, developmental language disorder, developmental dysphasia, or language impairment are used commonly to describe children whose communication skills are significantly delayed compared with their cognitive development.

The term specific language impairment is applied to children who experience difficulty acquiring language skills despite normal nonverbal intellectual ability. The structure of language consists of rules about word sounds phonology ; modifications of words to form plurals, possessives, and tenses morphology ; and sentence formation and grammar syntax.

The content of language consists of a store of known words lexicon and their meanings semantics. Functionally effective and appropriate communication depends on mastery of language pragmatic skills—the use of language in the context of social discourse.

Pragmatic behaviors include topic maintenance, reciprocity between speaker and listener, eye contact, and providing the partner with optimum information to facilitate conversation. If these were truly independent functions, these structural components of language might be expected to exist singly or in a wide range of combinations.

In clinical expression, however, problems with phonology, morphology, and syntax frequently cluster together and may affect only expressive abilities or both expression and comprehension of language. A pure form of receptive language deficit that involves intact expressive ability does not occur in children because children are unable to speak in the absence of verbal comprehension.

Verbal dyspraxia deserves special mention as a cause of language delay because it can result in completely unintelligible speech. As infants, affected children may have engaged in little or no babbling.

Translational research on early language development: Current challenges and future directions

Onset of speech often is delayed significantly, and once they begin to talk, articulation errors may be inconsistent, varying from sound to sound, word to word, sentence to sentence, or day to day. The deficit in motor praxis the ability to plan and execute coordinated movements appears to be at the level of motor planning, and the disorder often responds poorly to intensive speech therapy.

Verbal dyspraxia frequently accompanies other problems with language development and may be part of a generalized coordination disorder that affects feeding and fine motor and gross motor development.

Behavioral problems are common among children who have disorders of language development. As might be expected, they often experience a high degree of frustration, especially when they have difficulty understanding social situations or using language to regulate their own behavior or interactions with others.

Children who have limited communication skills frequently withdraw from social situations or become very anxious in unfamiliar settings. Young children may rely heavily on schedules and routines as means of ordering or controlling their environment.

As communication skills improve, many of these behaviors normalize. However, some degree of social impairment continues in older individuals whose language disorders persist long after they have acquired functional conversational language skills. Emerging evidence indicates that these children have difficulties correctly interpreting a variety of visual and auditory stimuli, including the emotional intentions and expression of others. The degree of familial clustering depends on the type of language disorder.

For example, there is no increased prevalence of speech, language, or learning disorders in families of children who have isolated expressive disorders compared with a three to four times higher prevalence among children who have mixed expressive and receptive disorders. Children who are economically disadvantaged and later-born children from large families in which siblings are closely spaced are more likely to exhibit delayed language development.

However, handedness and pre- and perinatal factors do not correlate with language development. Frequent episodes of otitis media may influence early typical and atypical language development in early childhood, but well-controlled studies have not shown it to be a cause of language delays, particularly for delays persisting beyond age 4 years. In children, bilateral brain lesions are more likely to disrupt language development than are unilateral or focal injuries.

Furthermore, in contrast to traditional concepts of regional anatomic specialization, recent findings from studies of adults who had acquired aphasia suggest that complex functions such as language and memory are the result of vast interconnected neural networks that are synchronized for specific activities across the cerebral cortex and subcortical regions.

Although fairly consistent anomalies of brain development have been found in the limited number of autopsy studies of adults who had lifelong disorders of language and learning, further research is needed to confirm that these abnormalities play a role in the disorders and that they represent physical manifestations of a genetically transmitted trait in familial cases of language and learning disorders.

Paroxysmal electrical abnormalities are more likely to be markers of cerebral dysfunction than causes of language disorder because treatment with antiepileptic agents has been largely unsuccessful in improving the language abilities of affected children. Initially, there is loss of verbal understanding, followed by deterioration in expressive communication ability.

Typical and Atypical Development: From Conception to Adolescence

Affected children may become completely mute and fail to respond even to nonverbal sounds, such as the ring of the telephone, a knock on the door, or a dog barking.

LKS is associated with an EEG pattern that shows electrical status epilepticus during slow-wave sleep. Such abnormalities may be unilateral or bilateral and may fluctuate from the right to the left hemisphere, although characteristically they are located over the temporal and parietal areas.

When seizures occur, they commonly are associated with eye blinking or brief ocular deviation, head dropping, and minor automatisms with occasional secondary generalization. Functional imaging in several cases of LKS has shown decreased perfusion in the posterior temporal cortical regions.

LKS is a prototype for considering a connection between EEG abnormalities and language disorders in the absence of clinical epilepsy.


Kanner noted that these children exhibited absent or delayed language development, inability to use language to convey meaning to others, and delayed echolalia, although their rote memory was excellent. Symptoms of autism begin before 3 years of age, and affected individuals have qualitative impairments in the areas of social interaction and communication and demonstrate restricted, repetitive, and stereotyped patterns of behavior, interests, and activities.

In the intervening 46 years since this initial report, a number of similar disorders, referred to broadly as the pervasive developmental disorders PDDshave been described. Individuals who have Asperger syndrome share many of the social deficits found in autism, but their overall language and cognitive development is not impaired. This disorder is not recognized in most cases until after 3 years of age, and many children actually appear precocious in their ability to talk.

Their preoccupation with unusual topics, which may change over time, often becomes intense and dominates their social interactions.