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.

BIBLIOGRAPHY

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.