A language disorder is a deficit or problem with any function of language and communication.
Speech and language disorders are extremely common. They can range from slow acquisition of language to sound substitution or stuttering to the inability to understand or produce and language at all. The federal Agency for Healthcare Research and Quality estimated in 2002 that communication disorders cost the United States between $30 and $154 billion annually in lost productivity and money spent on medical care, special education , and remediation.
Language disorders and the brain
Speech and language pathologists and neurologists (doctors who specialize in the brain and nervous system) have known for about 100 years that certain areas in the left hemisphere of the brain—Broca's area in the posterior frontal lobe and Wernicke's area in the temporal lobe—are centrally involved in language functions. Damage to Broca's area results in problems with language fluency: shortened sentences, impaired flow of speech, poor control of rhythm and intonation, and a telegraphic style with missing inflections. Damage to Wernicke's area produces speech that is fluent and often rapid, but with relatively senseless content, many invented words, and word substitutions.
With the invention of new technologies, including computed tomography (CT) scans and magnetic resonance imaging (MRI), several studies have looked at the language development in very young children with lesions in the traditional language areas of the brain. There is surprising agreement among the studies in their results: all find initial delays in language development followed by remarkably similar progress after about age two to three years. Lasting deficits have not been noticed in these children. Surprisingly, there are also no dramatic effects of laterality; lesions to either side of the brain seem to produce virtually the same effects. However, most of the data comes from conversational analysis or relatively unstructured testing, and these children have not been followed until school age. Nevertheless, the findings suggest remarkable plasticity and robustness of language in spite of brain lesions that would devastate an adult's language abilities.
Language disorders and hearing loss
Children with a hearing loss, either from birth or acquired during the first year or two of life, generally have a serious delay in spoken language development. The hearing loss occurs despite very early diagnosis and fitting with appropriate hearing aids. However, in the unusual case that sign language is the medium of communication in the family rather than speech, the child shows no delay in learning to use that language. Hearing development is always one of the first things checked if a pediatrician or parent suspects a language delay . The deaf child exposed only to speech will usually begin to babble ("baba, gaga") at a slightly later point than the hearing child. Recent work suggests that the babbling is neither as varied nor as sustained as in hearing children. However, there is often a long delay until the first words are spoken, sometimes not until age two years or older.
Depending on the severity of the hearing loss, the stages of early language development are also quite delayed. It is not unusual for the profoundly deaf child at age four or five years to only have two-word spoken sentences. It is only on entering specialized training programs for oral language development that the profoundly deaf child begins to acquire more spoken language. Often, such children do not make the usual preschool language gains until they reach grade school. Many deaf children learning English have pronounced difficulties in articulation and speech quality, especially if they are profoundly deaf, since they get no feedback in how they sound. A child who has hearing for the first few years of life has an enormous advantage in speech quality and oral language learning over a child who is deaf from birth or within his or her first year.
Apart from speech difficulties, deaf children learning English often show considerable difficulty with the inflection and syntax of the language, which marks their writing as well as their speech. The ramifications of this delayed language are also significant for learning to read, and reading proficiently. The average deaf high school student often only reads at fourth grade level.
Language disorders and mental retardation
Mental retardation can also affect the age at which children learn to talk. A mentally retarded child is defined as one who falls in the lower end of the range of intelligence , usually with an IQ (intelligence quotient) below 80 on some standardized IQ tests. There are many causes of mental retardation, including identified genetic syndromes such as Down syndrome , Williams syndrome , or fragile X syndrome .
Retardation can also be caused by damage to the fetus during pregnancy due to alcohol, drug abuse or toxicity, and disorders of the developing nervous system such as hydrocephalus . Finally, there are environmental causes following birth such as lead poisoning , anoxia, or meningitis .
Any of these situations is likely to slow down the child's rate of development in general, and thus to have effects on language development. However, most children with very low IQs develop some language, suggesting it is a relatively "buffered" system that can survive a good deal of insult to the developing brain. In cases of hydrocephalus, for example, it has been noted that children who are otherwise quite impaired intellectually can have impressive conversational language skills. Sometimes called the "chatterbox syndrome," this linguistic sophistication belies their poor ability to deal with the world. In an extreme case, a young man with a tested IQ in the retarded range has an apparent gift for acquiring foreign languages, and could learn a new one with very little exposure. For example, he could do fair translations at a rapid pace from written languages as diverse as Danish, Dutch, Hindi, Polish, French, Spanish, and Greek. He is, in fact, a savant in the area of language, and delights in comparing linguistic systems, although he does not have the mental capacity to live independently.
Adults should not consider retarded children to be a uniform class; different patterns can arise with different syndromes. For example, in hydrocephalic children and Williams syndrome, language skills may be preserved to a degree greater than their general intellectual level. In other groups, including Down syndrome, there may be more delay in language than in other mental abilities.
Most retarded children babble during the first year and develop their first words within a normal time span, but are then slow to develop sentences or a varied vocabulary. Vocabulary size is one of the primary components of standardized tests of verbal intelligence, and it grows slowly in retarded children. Nevertheless, the process of vocabulary development seems quite similar: retarded children also learn words from context and by incidental learning, not just by direct instruction.
Grammatical development, though slow, comes in the same way, and in the same order, as it does for normal IQ children. The child's conversation, however, may contain more repetition. The Down syndrome adolescent with an IQ of around 50 points does not seem to progress beyond the grammatical level of the normally intelligent child at three years, with short sentences that are restricted in variety and complexity. Children with Down syndrome are also particularly delayed in speech development. This is due in part to the facial abnormalities that characterize this syndrome, including a relatively large tongue. It is also linked to the higher risk they appear to suffer from ear infections and hearing loss.
Specific language impairment
Specific language impairment describes a condition of markedly delayed language development in the absence of any apparent handicapping conditions such as deafness, autism , or mental retardation. Specific language impairment (SLI) is also sometimes called childhood dysphasia, or developmental language disorder.
Children with SLI usually begin to talk at approximately the same age as normal children, but are markedly slower in their progress. They seem to have particular problems with inflection and word forms, such as leaving off endings when forming verb tenses (for example, the -ed ending when forming the past tense). This problem can persist much longer than early childhood, often into grade school and beyond, where these children encounter difficulties in reading and writing. The child with SLI often has difficulties learning language "incidentally," (picking up the meaning of a new word from context or generalizing a new syntactic form). This is in contrast to the normal child's development, where incidental learning and generalization are the hallmarks of language acquisition. Children with SLI are not cognitively impaired and are not withdrawn or socially aloof like the autistic child.
Very little is known about the cause or origin of specific language impairment, although evidence is growing that the underlying condition may be a form of brain abnormality. However, any such brain abnormality is not readily apparent with existing diagnostic technologies. When compared to other children, SLI children do not have clear brain lesions or marked anatomical differences in either brain hemisphere.
About one in six people, or 42 million individuals in the United States, have some type of communication disorder. About 28 million have speech, voice, or language problems associated with hearing loss, and about 14 million have similar problems not associated with impaired hearing. More than one million children in special education classes are categorized as having a speech or language disability.
Causes and symptoms
Language disorders can arise at many points in the language production process such as:
- from damage to the part of the brain that produces language
- from damage to the part of the brain that understands language
- from hearing loss
- from damage to the muscles and tissues of the mouth and throat needed for speech (e.g. cleft palate )
- from neurological disorders that interrupt the transmission of information necessary to receive and produce language
- from unknown (idiopathic) causes
Symptoms of language disorders vary widely, but include:
- slow acquisition of speech and language
- inability to make the physical sounds associated with language production (mutism)
- failure to make sense of spoken or written words
- inability to speak under certain social circumstances (selective mutism)
- transformations of words or sounds when speaking
- inability to recall known words
When to call the doctor
Parents should talk to their pediatrician immediately if their child appears to have hearing impairment . They should also consult with their doctor if the child does not babble or begin to use single words within the normal time frame. Parents of older children may need a referral to a speech and language specialist if their child stutters, lisps, has difficulty forming words or producing coherent speech, or exhibits certain learning disabilities.
Speech and language disorders are usually diagnosed by a speech and language pathologist, often with the help of a pediatrician, audiologist (hearing specialist), and neurologist. Many assessment tests are designed specifically for use in children, including the Clinical Evaluation of Language Fundamentals (also available in Spanish); the Preschool Language Scale (also available in Spanish); the Test of Language Development, Primary; and the Test of Language, Intermediate. There are assessments designed to evaluate speech production, such as the Goldman-Fristoe test of Articulation.
Treatment varies, depending on the type and cause of the language disorder. However, in all language disorders and delays, early intervention is key to improvement. Many educators of the deaf now urge early compensatory programs in signed languages, because the deaf child shows no handicap in learning a visually based language. Deaf children born to signing parents begin to "babble" in sign at the same point in infancy that hearing infants babble speech, and proceed from there to learn a fully expressive language. However, only 10 percent of deaf children are born to deaf parents, so hearing parents must show a commitment and willingness to learn sign language. Furthermore, command of at least written English is still a necessity for such children to be able to function in the larger community.
Speech therapy can be a considerable aid to many children with language disorders For example, it can help to make a Down syndrome child's speech more intelligible. Despite the delay, children with Down syndrome are often quite sociable and interested in language for conversation.
Surgery, followed by speech therapy, can correct physical deformities, such as cleft palate, that interfere with speech production.
Psychotherapy can help older children whose language disorders are psychologically based.
Prognosis varies on an individual basis, depending on the cause, type, and severity of the language disorder. Those children who receive early intervention therapies are more likely to have a better outcome than those for whom services are delayed.
Many language disorders are not preventable. However, those that arise from damage to the fetus due to the mother's use of drugs or alcohol during pregnancy can be prevented by avoiding these substances.
Language is such a critical part of our society that parents are justly concerned when their child has a language disorder. The parents' approach to the disorder can greatly influence the child's self-image, self-esteem , and ultimately his or her success in reaching the fullest language potential.
Speech pathologist —An individual certified by the American Speech-Language-Hearing Association (ASHA) to treat speech disorders.
Bahr, Diane Chapman. Oral Motor Assessment and Treatment: Ages and Stages. Boston: Allyn and Bacon, 2001.
Freed, Donald B. Motor Speech Disorders: Diagnosis & Treatment. San Diego: Singular Pub. Group, 2000.
Conti-Ramsden, Gina. "Processing and Linguistic Markers in Young Children with Specific Language Impairment." Journal of Speech, Language, and Hearing Research 46, no. 5 (October 2003): 1029–38.
Fujiki, Martin, et al. "The Relationship of Language and Emotion Regulation Skills to Reticence in Children with Specific Language Impairment." Journal of Speech, Language, and Hearing Research 47, no. 3 (June 2004): 637–47.
Nation, Kate, et al. "Hidden Language Impairments in Children: Parallels Between Poor Reading Comprehension and Specific Language Impairment?" Journal of Speech, Language, and Hearing Research. 47, no. 1 (February 2004): 199–212.
American Speech-Language-Hearing Association. 10801 Rockville Pike, Rockville, MD 20852. (800) 638-8255. Web site: <www.asha.org>.
Tish Davidson, A.M. Jill De Villiers, Ph.D.
"Language Disorders." Gale Encyclopedia of Children's Health: Infancy through Adolescence. . Encyclopedia.com. (August 16, 2017). http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/language-disorders
"Language Disorders." Gale Encyclopedia of Children's Health: Infancy through Adolescence. . Retrieved August 16, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/language-disorders
Human communication and socialization to a large degree occur through language, which is a symbol system used to represent, convey, and interpret ideas, thoughts, and feelings. Typically one language user (a sender) arranges words or other vocabulary symbols (e.g., gestures, as used in sign language) to express particular intentions or ideas to at least one other language user (a receiver). While many equate language with speech, they are not identical. Speech, along with writing and pantomime, is just one of the channels used to express language. Language is understood through reciprocal channels, like listening, reading, or interpreting manual signs.
Language involves a number of interactive systems related to its content, form, and use. Semantics refers to a system of concepts or meanings. The "mental dictionary" that contains vocabulary symbols for expressing and interpreting these concepts is called the lexicon. Morphology is concerned with word formation. Morphemes, the smallest units of language that signal meaning, can be single words or they can be add-ons, like possessive or past tense markers, that change the meaning of their root words. Phonology refers to the sound system of language (vowels and consonants), and to stress and melody patterns. Although phonology is most obviously connected with the speech channel, there is ample evidence that adults also access phonology when they read silently. Syntax involves the ways that words representing different parts of speech can be sequenced to construct acceptable and interpretable phrases, clauses, and sentences. To illustrate, English syntax allows only certain combinations of nouns and verbs (e.g., "The girl ate" is acceptable, but "Ate the girl" is not); and different word orders signal different meanings (compare "The girl told the boy" with "The boy told the girl"). Finally, pragmatics is concerned with the ways in which language is used to communicate particular purposes and intents. For example, pragmatics involves the difference between what someone actually says and what they mean by it, as when teasing or being sarcastic. The particular communicators, their shared assumptions and knowledge, and their current social context all are important pragmatic considerations.
Language disorders can take the form of difficulty expressing and/or understanding ideas and intentions through any or all language channels, and can be reflected in disturbances of any or all language systems. Because language is not identical to speech, language disorders are different from speech disorders. The latter may reflect, among other things, abnormalities in vocal tract structures such as the lungs, larynx (commonly known as the voice box), and oral articulators (e.g., tongue, lips, jaw), or difficulties in managing the breathstream, which provides the energy source for speech.
Language disorders in older adults
As people age, they tend to experience changes in language functioning. Some aspects, like the use or understanding of complex syntax, typically show signs of decline. Others, like vocabulary knowledge, improve with age, though the older one gets the more difficult it becomes to retrieve from the lexicon the precise words one wants. While full-blown language disorders are not the norm for elderly people, some particular language disorders are more likely to co-occur with advancing age, because the medical conditions that cause them primarily affect older individuals. These conditions include stroke and dementing illnesses. Their common language after effects include aphasia, right hemisphere communication disorders, and the language of generalized intellectual impairment.
Aphasia is an acquired language disorder. Typically, it is the result of damage to the left side of the brain, which for most individuals is "dominant" for language functions. The damage that induces aphasia is usually cortical and peri-Sylvian, which means that it affects the outermost layers of brain cells that surround the Sylvian fissure (see Figure 1). Most often caused by stroke, aphasia also can result from other conditions, like head trauma, when the brain damage predominantly affects left peri-Sylvian regions.
Aphasia affects both the expression and interpretation of language, through all of its channels, but to different degrees in different individuals depending on the nature and extent of brain damage. Language changes that reflect sensory deficits, such as hearing loss, do not constitute aphasia. Also, language impairment in aphasia is disproportionate to, and cannot be explained by, other types of cognitive changes, such as memory problems.
A word retrieval deficit, or difficulty in selecting the precise words one wants to use from an unaltered lexical store, is a universal symptom of aphasia. These word retrieval difficulties, often called anomia, are more frequent and less likely to be resolved than the word retrieval challenges of normal aging. It is important to note, though, that word retrieval deficits are common after any kind of brain damage; thus, they are not diagnostic. The other language systems are variably affected in adults with aphasia.
Classical views of aphasia divide it into syndromes or types, such as Broca's and Wernicke's aphasia. Each type has some expressive and receptive characteristics that grossly differentiate it from other types of aphasia, and that are presumed to stem from damage to particular peri-Sylvian regions in the left cerebral hemisphere. However, it has become clear that damage confined to a particular brain area (e.g., Broca's or Wernicke's area; see Figure 1) does not generate a lasting aphasia of the same type. More generally, the accuracy and value of aphasia syndrome classifications, as well as the correspondence between language disorder profiles and brain lesion locations, are the subject of much debate (see, e.g., commentaries following an article by Yosef Grodzinsky). Research is ongoing to specify the complex relationships among normal brain anatomy and its contribution to the functioning of various language systems, as well as the precise ways in which particular kinds of brain damage produce particular types of language symptoms.
Right hemisphere language disorders also can result from stroke. This time the stroke affects the side of the brain that is not dominant for language; typically, as the name implies, the right hemisphere. These disorders have been systematically studied since the mid-1980s. Because so little is known about the nature of right hemisphere language deficits, there is not yet an appropriate diagnostic label. However, some descriptive generalizations are possible. Strokes that are restricted to the right hemisphere in older adults appear to have little effect on phonology, morphology, or syntax, and their consequences for lexical-semantic processing are unclear. But adults with right hemisphere damage can be particularly impaired in pragmatic aspects of language. As senders, for example, they may have special difficulty supplying content that is appropriate to the communicative circumstances, by assuming that a receiver knows something that he or she does not know, or by being too wordy, too terse, too detailed, too tangential, and/or too vague. As receivers, they may be particularly impaired at understanding implications that are not directly stated, such as those conveyed by nonliteral language (e.g., jokes or irony) or other ambiguous information. These difficulties, while not always immediately obvious to others, can render adults with right hemisphere damage quite socially disadvantaged.
Finally, the language of generalized intellectual impairment (Wertz) is a diagnostic label that refers to language disorders resulting from neurologically degenerative processes such as Alzheimer's disease. In people with the language of generalized intellectual impairment, both sides of the brain typically are affected by the degenerative process. Thus, these individuals may have a constellation of language deficits that includes any or all that typify aphasia and right hemisphere language disorders. In addition, however, they generally have other cognitive deficits, such as difficulties with memory and attention, that cause, contribute to, or confound their language symptoms.
Many clinicians, including most medical professionals, use the term aphasia to refer to language disorders that accompany neurologically degenerative conditions. However, many clinical aphasiologists, like Robert T. Wertz, find value in distinguishing the two labels, in part because prognoses and treatment options differ substantially. People who have strokes improve, sometimes dramatically. This occurs naturally as the brain heals, as well as through language therapy. In addition, as alluded to earlier, the nature of the language impairments typically is different in adults who have simple strokes versus dementias. The language deficits in adults with dementing conditions may be rooted in, or are at least significantly complicated by, profound cognitive impairments, such as difficulties in learning and remembering new material. To illustrate, immediately after they hear a brief prose passage, adults with incipient dementia can retell it normally; but after only fifteen minutes, they may recall nothing about it. This is not the case for adults with the other language disorders reviewed above. For them, the difference between immediate story retelling and short-term recall is much less extreme, and may be on par with that for normally aging adults (e.g., Bayles and Kaszniak).
Language deficits in early Alzheimer's disease and other progressive conditions
As noted above, memory deficits are among the earliest hallmarks of the onset of probable Alzheimer's disease (AD). In the language domain, individuals with suspected early AD have predominantly lexical-semantic impairments. For example, they may have particular difficulty naming pictures, naming items that are described to them (e.g., "what do you use to tell time?"), and generating more than a few common examples of words that start with a given letter of the alphabet. They may also wander from the topic of a conversation and be vague in what they say. Syntax, morphology, and phonology are relatively preserved until the later stages of the disease. Thus, early in the course of AD, language production may be perfectly structured, but "empty" or lacking in content (e.g., "The thing is over there, you know").
Progressive aphasia is a poorly understood condition in which language deteriorates over time, but which only infrequently is identified at autopsy as AD (Mesulam). Like AD, symptom onset and decline are gradual, but in contrast to most cases of AD, language difficulties are the earliest and the primary signs of trouble. While non-language aspects of cognition reportedly are retained for several years after the onset of language symptoms, deficits may be evident with careful testing. Once clearly identified, non-language cognitive abilities may decline less rapidly than language skills.
Again, progressive aphasia may manifest in various ways. Language expression may be effortless and well-formed but low in content, as in early AD, or it may be effortful and "telegraphic" in quality, consisting primarily of nouns and verbs (e.g., "Boy - girl - cookie - falling"). Likewise, language comprehension may be relatively good or poor. According to Mesulam, progressive aphasia often is associated with a loss of nerve cells in relatively focal cortical areas of the brain, but precise causal factors are unclear.
Complications in diagnosing language disorders in older adults
During the aging process, changes in bodily systems such as vision, hearing, or motor control for speech may cause changes in everyday language activities, such as reading the newspaper, following a conversation, or speaking clearly on the telephone. But as implied in the discussion of aphasia, one must be careful to account for or rule out difficulties of this sort before diagnosing a language (or other cognitive) disorder. Depression, while not a normative condition in older adults, is worth noting here as well, because it can reduce performance in testing situations and thus, without careful assessment, masquerade as a language or other cognitive disorder.
Education, and potentially related factors like literacy and language practice or use over the lifespan, also may complicate assessment and diagnosis of language disorders. Performance on aphasia tests, for example, shows a clear relationship to education. As such, unless an examiner is appropriately cautious, traditional assessments may overdiagnose difficulties in people with little formal education or language proficiency. On the other side of the coin, many measures may not be sufficiently sensitive to detect definite changes in highly educated or literate individuals.
Connie A. Tompkins Margaret T. Lehman-Blake
See also Brain; Dementia; Speech; Stroke.
Bayles, K. A. "Management of Neurogenic Communication Disorders Associated with Dementia." In Language Intervention Strategies in Adult Aphasia, 3d ed. Edited by R. Chapey. Baltimore: Williams & Wilkins, 1994. Pages 535–545.
Bayles, K. A., and Kaszniak, A. W. Communication and Cognition in Normal Aging and Dementia. Boston: College-Hill, 1987.
Fromkin, V., and Rodman, R. An Introduction to Language, 4th ed. New York: Holt, Rinehart and Winston, 1988.
Grodzinsky, Y. "The Neurology of Syntax: Language Use Without Broca's Area." Behavioral and Brain Sciences 23 (2000): 1–71.
Melvold, J. L.; Au, R.; Obler, L. K.; and Albert, M. L. "Language During Aging and Dementia." In Clinical Neurology of Aging, 2d ed. Edited by M. L. Albert and J. E. Knoefel. New York: Oxford University Press, 1994. Pages 329–346.
Mesulam, M.-M. Principles of Behavioral and Cognitive Neurology, 2d ed. Oxford: Oxford University Press, 2000.
Tompkins, C. A. Right Hemisphere Communication Disorders: Theory and Management. San Diego: Singular, 1995.
Wertz, R. T. "Neuropathologies of Speech and Language: An Introduction to Patient Management." In Clinical Management of Neurogenic Communicative Disorders, 2d ed. Edited by D. F. Johns. Boston: Little, Brown and Company, 1985. Pages 1–96.
Wingfield, A., and Stine-Morrow, E. A. L. "Language and Speech." In The Handbook of Aging and Cognition. Edited by F. I. M. Craik and T. A. Salthouse. Mahwah, NJ: Erlbaum, 2000. Pages 359–416.
"Language Disorders." Encyclopedia of Aging. . Encyclopedia.com. (August 16, 2017). http://www.encyclopedia.com/education/encyclopedias-almanacs-transcripts-and-maps/language-disorders
"Language Disorders." Encyclopedia of Aging. . Retrieved August 16, 2017 from Encyclopedia.com: http://www.encyclopedia.com/education/encyclopedias-almanacs-transcripts-and-maps/language-disorders
Problem with any function of language and communication.
In adults, much of what is known about the organization of language functions in the brain has come from the study of patients with focal brain lesions. It has been known for hundreds of years that a left-hemisphere injury to the brain is more likely to cause language disturbance—aphasia —than a right hemisphere injury, especially but not exclusively in right-handed persons. For about a hundred years, certain areas in the adult left hemisphere—Broca's area in the posterior frontal lobe, and Wernicke's area in the temporal lobe—have been identified as centrally involved in language functions. However, researchers in the field of adult aphasia are divided over the exact role these brain areas play in language processing and production. Damage to Broca's area results in marked problems with language fluency; with shortened sentences, impaired flow of speech, poor control of rhythm and intonation (known as prosody); and a telegraphic style, with missing inflections and function words. In contrast, the speech of Wernicke's aphasics is fluent and often rapid, but with relatively empty content and many neologisms (invented words) and word substitutions. It was initially believed that the two areas were responsible for output (Broca's) versus input (Wernicke's), but research does not confirm such a simple split.
Other theories ask whether the two areas might be differentially involved in syntax versus semantics, or phonology versus the lexicon, but the picture is not clear. Some have argued that adult aphasic patients, once they are stable after their injury or stroke, employ many compensatory devices that conceal or disguise the central character of their language difficulties. It then becomes more difficult to assess what is missing or disturbed because the difficulties are overlaid by new strategies, and perhaps new areas of the brain taking over functions for the damaged areas.
Infants and young children who suffer focal brain lesions in advance of acquiring language provide valuable information to neuroscientists who want to know how "plastic" the developing brain is with respect to language functions. For instance, is the left hemisphere uniquely equipped for language, or could the right hemisphere do as well? What if Broca's or Wernicke's areas were damaged before language was acquired? Thirty years ago a review of literature on children who had incurred brain lesions suggested that, unlike the case of adults, recovery from language disruption after left-brain damage was rapid and without lasting effect. Researchers concluded that the two hemispheres of the brain were equipotential for language until around puberty , and that this allowed young brain-damaged children to compensate with their undamaged right hemisphere.
However, several studies suggested that left-brain damage caused greater disruption to language than right-sided damage even in the youngest subjects. Children known to be using only their right hemisphere for language (because they had undergone removal of the left hemisphere for congenital abnormalities) demonstrated subtle syntactic deficits on careful linguistic testing, but the deficits failed to show in ordinary conversational analysis. Almost all of these studies were retrospective, that is, they looked at the performance of children at an older age who had suffered an early lesion. Furthermore, the technology for scanning the brain and locating the lesion site, then carefully matching the subjects, was much less developed.
With the invention of new technologies including CT scans and Magnetic Resonance Imaging (MRI), several studies have been conducted to look prospectively at the language development of children with focal, defined lesions specifically in the traditional language areas. There is surprising concordance among the studies in their results: all of them find initial (but variable) delays in the onset of lexical, syntactic, and morphological development followed by remarkably similar progress after about age two to three years. Lasting deficits have not been noticed in these children. Surprisingly, there are also no dramatic effects of laterality: lesions to either side of the brain seem to produce virtually the same effects. However, most of the data comes from conversational analysis or relatively unstructured testing, and these children have not been followed until school age.
Until those detailed studies are extended, it is difficult to reconcile the differing results of the retrospective and prospective studies. Nevertheless, the findings suggest remarkable plasticity and robustness of language in spite of brain lesions that would devastate an adult's system.
Jill De Villiers Ph.D.
Byers Brown, B., and M. Edwards. Developmental Disorders of Language. San Diego: Singular Publishing, 1989.
Miller, J. Research on Child Language Disorders: A Decade of
Progress. Austin, TX: Pro-ed, 1991.
"Language Disorder." Gale Encyclopedia of Psychology. . Encyclopedia.com. (August 16, 2017). http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/language-disorder
"Language Disorder." Gale Encyclopedia of Psychology. . Retrieved August 16, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/language-disorder