DISORDERS OF LANGUAGE

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CHAPTER 3 DISORDERS OF LANGUAGE

There are two main schools of thought in the history of neurogenic language disorders, both of which have relevance to modern aphasiology. The first, the Wernicke-Lichtheim-Geschwind tradition, emphasized that primary language functions are represented in discrete regions of cortex (“centers”) and that the activities of these loci are integrated through connecting fiber tracts. The Wernicke-Lichtheim scheme consisted of a center for motor images of words, located in the posterior third of the inferior frontal convolution (Broca’s area), as well as a center for acoustic images of words (Wernicke’s area). A fiber tract (arcuate fasciculus) joined the two centers, with the flow of information running from posterior to anterior. A third center for concepts was located in the extrasylvian cortex, with an outflow to Broca’s area and input from Wernicke’s area. There was an output from Broca’s area to the motor cortex and an input to Wernicke’s area from the auditory cortex. This simple scheme systematized the main perisylvian and transcortical aphasia syndromes observed before 1885 and predicted the existence of a syndrome as yet unobserved at that time: conduction aphasia. The Wernicke-Lichtheim model was later refined by members of the Boston School, principally Frank Benson and Norman Geschwind, with the addition of three new syndromes, and the inclusion of the inferior parietal lobule as language cortex (see Benson and Ardila, 1996).

The second main stream is represented by neurologists such as Hughlings Jackson, Sigmund Freud, and Aleksandr Luria who conceived of language as represented in broader hierarchical cortical zones or gradients, organized around the centers of the Wernicke-Lichtheim model. The role of connecting tracts was deemphasized. Luria’s aphasiology preserves the anteroposterior schema of the Wernicke-Lichtheim model but redefines localization of language as hierarchical and distributed. Modern clinical aphasiology is based on the classical syndromes described in the Wernicke-Lichtheim tradition and their modifications. Concepts of their localization, however, have come to be shaped further by ongoing clinicopathological observation and functional neuroimaging, and current views on the localization of language are not too distant from those of the Jackson-Freud-Luria tradition. Linguistic ideas have also become part and parcel of modern aphasiology. A glossary of important linguistic terms and concepts is given in Table 3-1.

TABLE 3-1 Essential Linguistics Concepts

Phonological	Phonology is the study of the structure and patterning of the sounds of language. Many of the clinical features of language disorders are phonological. The units of analysis are phonemes, which can be defined as the basic meaning-distinguishing sounds (essentially consonant and vowel sounds) of the language.
Lexical	Whereas phonology is concerned with the patterning of sounds within a word, and is therefore a sublexical discipline, lexicology is concerned with the whole word as a single entity. At a lexical level, there is a dichotomy that is fundamental to the understanding of aphasic disorders, because aphasic variants affect the two classes of words differentially. The open class, so-called because it is conceptually unlimited and new items are steadily added as vocabularies increase, consists principally of nouns, verbs, adverbs, and adjectives—that is, words that refer to specific objects, actions, and attributes and that convey substantive content. The closed class, which is conceptually limited and does not increase in size as vocabularies increase, consists of articles (e.g., “a,” “the,” “that”), conjunctions (e.g., “and,” “but”), pronouns (e.g., “you,” “they”), and prepositions (e.g., “up,” “along,” “below”). The distinction between open- and closed-class words parallels the distinction between the meaning of a sentence (semantics) and the form or sequential structure of a sentence (syntax).
Morphological	Morphology concerns the internal structure of words. The aspect of morphology that is most important for understanding language disturbances is word formation, or the construction of a new word from an existing word by adding an affix. This can be derivational, whereby an adjective such as “good” is converted to a noun such as “goodness,” or inflectional, whereby a word is changed to suit the grammar of a sentence; for example, “run” might become “running,” or “pencil” might become “pencils.” Because the suffixes “-ing” and “-s” cannot stand alone, they are referred to as bound morphemes.

LANGUAGE PRODUCTION

At a clinical level, language disorders are more easily recognized and identified in language production, either spoken or written, than in disturbances of comprehension. Production consists of three broad stages: conceptualization, formulation, and overt execution. The first two of these stages are described in detail in the following sections. From a neuroanatomical perspective, conceptualization (the development of an intention to speak, and a decision about what will be said) depends on the dorsolateral prefrontal cortex. Formulation (the conversion of ideas into the structure of spoken language) depends on Broca’s region. Execution is the production of physical speech and depends on all of the motor mechanisms associated with speech (see Duffy, 2005).

Conceptualization

This is a largely prelinguistic phase that involves the development of an intention to speak and a decision as to what will be said. Development of an intention and a decision about the message to be conveyed is often referred to as macroplanning. From that point on, the message must be reshaped into a particular set of logical relationships (propositions) that can be expressed in terms of the syntactic and semantic structure of language. This is often referred to as microplanning. Propositions form a link between thought and its expression in language. It is noteworthy that this concept was anticipated by the British neurologist Hughlings Jackson, who regarded it as essential for understanding the relationship between thought and speech in aphasia. Conceptualization depends on connectivity between extrasylvian association cortex and the classical perisylvian language axis, a concept borne out by functional neuroimaging (see Blank, Scott, Murphy, et al, 2002).

Formulation

This phase deals with the conversion of propositions into actual sentences (sentence encoding). It is governed directly by the rules of syntax and semantics and consists of two important components. The first involves the selection of appropriate open class of lexical items (see Table 3-1) to convey the intended meaning. The linguistic concept of selection is of central importance in aphasic disorders. Selection implies the possibility of choice among alternatives, and errors in selection manifest clinically as paraphasias. A paraphasia has two essential features: (1) It is an error of selection resulting in the substitution of a word or part of a word with a frequently incorrect or inappropriate alternative, and (2) it is unintended. Selection processes occur at the phonemic and the semantic levels (see Table 3-1). In neuroanatomical terms, selection processes are heavily, but not exclusively, dependent on posterior perisylvian association cortices. The second component of formulation involves the genesis of correctly ordered positional slots into which the words of the sentence are inserted. These sequentially ordered schemas are often called sentence frames, and their construction is contributed to and defined by closed class (function) words and bound morphemes (see Table 3-1) Sentence frames are constructed according to the rules of syntax (see Table 3-1). The functional neuroanatomy of syntactic processing is complex, involving a network of left perisylvian structures, and it appears that Broca’s area is a key nodal structure within this network. Disorders of syntax, including Broca’s aphasia, occur most prominently with lesions involving the anterior aspects of the perisylvian language zone.

Fluency

The division of language disturbances into fluent and nonfluent is the most fundamental and clinically appreciable dichotomy in diagnostic aphasiology. The major aphasia syndromes are encompassed within the distinction of fluent versus nonfluent (see Table 3-2).

TABLE 3-2 The Fluent-Nonfluent Distinction

	Nonfluent Production	Fluent Production
Anatomical	Anterior (prerolandic) language areas	Posterior (postrolandic) language areas
Fundamental disorder	Sequential organization (conceptualization, formulation)	Selection
Syndrome	Perisylvian	Perisylvian
	Aphemia	Pure word deafness
	Broca’s aphasia	Wernicke’s aphasia
	Extrasylvian	Conduction aphasia
	Transcortical motor aphasia	Extrasylvian
		Transcortical sensory aphasia
		Anomic aphasia

Note: Mixed transcortical aphasia and global aphasia are associated with clinically nonfluent production but also involve an underlying selection disorder.

Fluent language output in an aphasic patient is defined by the use of sentences that are syntactically intact but are semantically compromised because of a selection disorder. The following example, taken from a description of a severe form of fluent dysphasia, namely jargonaphasia (a variant of Wernicke’s aphasia), illustrates this point:¹

“This guy has got to this thing, this thing made out in order to slash immediately to all of the windpails. … This is going right over me from there, that’s up to is 5 station stuff from manatime, and with that put it all in and build it all up so it will all be spent with him conversing his condessing.”

The sequential relationships between grammatical entities in the passage are preserved. It is the closed class entities that are primarily affected by errors in selection, resulting in phrases that are devoid of meaning, and jargonistic substitutions (neologistic paraphasias) such as “manatime,” and “condessing.” Prosodic features are characteristically retained. Prosodic features are rhythmic and emphatic aspects of language production that allow the listener to appreciate whether the speaker is, for example, asking a question or making a statement.

Nonfluent aphasic output, in contrast, is characterized by a dissolution of syntactic structure; in particular, the production of closed class words is affected. The following are examples of nonfluent language:

1. A soldier talking about a bullet wound to his head on the battlefront: “Well … well … front … well … advance … well … bullet … well … nothing much … hospital … operation … well … speech … speech … speech. …”²

2. In response to the question “Have you played no games?”: “Played games, yes, played one, daytime, garden.”³

3. Explaining a readmission to hospital: “Ah … Monday … ah, Dad and Paul and Dad … hospital. Two … ah, doctors … and ah … thirty minutes.”⁴

In contrast to the fluent output, these utterances are devoid of syntactic structure, exemplified by the lack of closed class words, and the relative excess of open class words. This pattern constitutes agrammatism. Nevertheless, there is appropriate selection of open class words (nouns and verbs), and as a consequence nonfluent output does not entirely have the “empty” character of fluent output. The length of phrases is heavily reduced in agrammatic disorders.

Paraphasia and Other Deviations

Paraphasias

Paraphasias are defined as unintended utterances. In essence, there is a failure of selection at the phonemic level, producing a phonemic (literal) paraphasia (e.g., “I drove home in my lar”) or at a word (lexical) level (e.g., “I drove home in my wagon”), producing a verbal paraphasia (Table 3-3). Paraphasias are said to be neologistic when the unintended word is heavily contaminated with extraneous phonemes and, as a result, contains juxtapositions of sublexical fragments that are not characteristic of the language (phonemic neologisms) and are nonsensical in context. For example:⁵

TABLE 3-3 Paraphasias and Other Selection Errors

Type	Examples
Phonemic (literal)	“glear” instead of “clear”
	“spink” instead of “sphinx”
	“gedrees” instead of “degrees”
	“tums” instead of “tongs”
Conduit d’approche (successive phonemic approximations to a target word)	“trep”→“tretz”→“fretful”→“pretzel”
Verbal
Formal (similar form, different meaning)	“dare” instead of “pear”
Morphemic (assembled from legal morphemes)	“man-a-time,”^* “summer-ly”
Semantic (substituted word belongs to the same general category)	“train” instead of “car”
	“Taj Mahal” instead of “pyramid”
	“cloth” instead of “blanket”
	“seahorse” instead of “unicorn”
Circumlocutions (word substituted with a phrase of the same meaning)	“drinking container” instead of “cup”