Explanations for the Concept of Apraxia of Speech
Total Page:16
File Type:pdf, Size:1020Kb
8 Explanations for the Concept of Apraxia of Speech HUGH W. BUCKINGHAM, JR. The term APRAXIA OF SPEECH has had an extremely variable history. It has been used to describe different types of behaviors, in different types of patients, and under different stimulus conditions. The term has been used, often with qualifying modifiers, to describe syndromes or parts of syn- dromes. The different conceptualizations of apraxia in general have en- gendered inconsistencies for the definition of apraxia of speech. I propose that under certain interpretations there are additional forms of apraxia of speech that differ from the frontal lobe and insular speech apraxias. It is a sine qua non that certain phonological functions operate in ways that do not acknowledge the physical descriptions that characterize the sensory-motor practic functions of the nervous system (Goldsmith, 1995). Much of the impasse and tension in the discussions of apraxia of speech is due to the gulf between the explanatory vocabularies of the men- tal versus the physical sciences (J. Jackson, 1931b). Phonological functions involve selecting and sequencing of phoneme-like units that speakers BE- LIEVE themselves to be uttering. In actuality, they are uttering sounds, or PHONES, which may then be considered as being produced by nervous fir- ings giving rise to complex and synchronous muscular contractions that result in acoustic impingements on the air. The description of phonologi- cal processing should not imply that phonemes "are sounds" or that they are articulated. Phonemes ARE NOT SOUNDS. They are "psychologically real" abstract categories for which no invariant factor, articulatory or acoustic, has yet been found--nor is ever likely to be found. Furthermore, the subphonemic errors made by certain patients typically involve dis- 269 ACQUIRED APHASIA, THIRD EDITION Copyright 1998 by Academic Press. All rights of reproduction in any form reserved. 270 Hugh W. Buckingham, Jr. turbed limb-praxic function for the vocal tract "limbs" and the motor com- mands for outputting speech sounds (phones) and prosodymthe phonemes and their sequential order having been somehow readied at higher levels. 1 The result is an effortful, groping speech output, usually seen when the left frontal region is damaged in, around, and/or under- neath the foot of the third convolution, encompassing pars opercularis (Broadman Area 44) and/or pars triangularis (Broadman Area 45). A close analysis of the historical development of apraxia and of its many current characterizations (Rothi & Heilman, 1997; Rothi & Heilman, 1996) explains why the apraxias in general permit alternate explanations: one implicating disconnection lesions (lesions that disengage centers) and an- other implicating cortical lesions of the centers themselves. This state of af- fairs has unwittingly resulted in confusion over the issue of apraxia in gen- eral and its derived notion of "apraxia of speech," "rekindled" by Darley (Sasanuma, 1989, p. xii) but originally identified by Liepmann (Rosenbek, 1993, p. 444). Historical Background Liepmann's Precursors Before the work of John Hughlings Jackson (1931c) and Hugo Liep- mann (1900; also see Eling, 1994; Kimura, 1980; Rothi & Heilman, 1996), 1. The wording here is dangerously close to the fallacy that John Hughlings Jackson (1878/1931b) warned against. He believed that a "psychical state" (an "idea of a word" or simply "a word") cannot produce an articulatory movement, which is clearly a physical phenomenon. Rather, it was "discharge of the cells and fibers of the anatomical substra- tum of a word [which] produces the articulatory movement" (p. 156). Jackson stated, "In our studies of diseases of the nervous system we must be on our guard against the fallacy ... that somehow or another an idea produces a movement" (p. 156). Phonemes, like words, are abstractions and like the "psychical" elements of Jackson do not "fine away" into physical articulatory production. This dualism of Jackson is suggestive and should be carefully considered when dealing with phonemes and neurological theories of speech production; that is, the problems are precisely what Jackson was defining last century (Buckingham, 1986b; Engelhardt, 1975). Phonemes are mentalistic constructs of the mind; they have psychological, not physical, reality. A phoneme is an abstract unit, which by its ontological nature cannot be uttered. What are actually produced are phones (sounds). Phones that pattern together, that are phonetically similar, and that most often are found in complementary distribution are referred to as the ALLOPHONES of a phoneme. The Greek morpheme allo- means closely related, being one of a group whose members together con- stitute a structural unit. Phones group together as allophones, whose members together constitute a structural unitmthe phoneme. Fromkin and Rodman (1993) quote the early twentieth century linguist, Edward Sapir: "In the physical world the naive speaker and hearer actualize and are sensitive to sounds, but what they feel themselves to be pro- nouncing and hearing are 'phonemes'" (p. 172). 8 Explanationsfor the Concept of Apraxia of Speech 271 who are usually credited with developing the notion of apraxia (Brown, 1988b; Harrington, 1985, 1987), Paul Broca (1861/1960)considered two al- ternative explanations for the speech problem of his patient, Leborgne (Tan) (Clarke, 1980; Lebrun, 1989; Schiller, 1992; yon Bonin, 1960). The first, which he eventually adopted, was that the patient had lost his "faculty of articulate speech. ''2 This was an intellectual faculty and consisted of the "memory for the procedure one has to follow in order to articulate the words" (p. 54), an idea attributed to Bouillaud. Broca (1861/1960) sug- gested that this modular faculty may be "a kind of memory." He writes, "This memory is not in relation with any other memory or the rest of the intelligence" (p. 53). It was not a general memory, but one specifically slot- ted to remember how to coordinate articulatory movement. There is an in- triguing similarity with Liepmann's notion of "movement formulas." These were kinetic memories; they were procedural but were closer to the kinetic memories of Liepmann than to Liepmann's so-called "movement formulae." Broca (1861/1960) also considered the possibility that aphemia might "be a kind of locomotor ataxia, limited to the articulation of sounds" (p. 54). According to Broca, this option would imply that the disorder would not be the loss of an intellectual memorial faculty, "which belongs to the think- ing part of the brain" (p. 54), but rather "it would only be a special case of the general coordination of actions, a faculty which depends on the motor centers of the central nervous system" (p. 54). At the time of Broca's paper, the "Bell-Magendie" sensorimotor dichotomy had not reached the cerebral cortex (Young, 1990). Consequently, it was difficult to conceive of a CORTI- CAL motor (nonintellectual) system, and therefore damage to the cortex should only disrupt "intellectual faculties"; motor organization and func- tion were not thought to be intellectual. Broca (1861/1960) states quite suc- cinctly, "Everyone knows that the cerebral convolutions are not motor or- gans" (p. 70). Subsequent to Broca's presentation, the stage was set for arguments as to whether Broca's aphasia involves language or speech, al- though in 1861, the discussion was whether it was an intellectual impair- ment of a modular form of memory for speech-movement procedures or a nonintellectual problem with locomotion, not unrelated to our present- day quandaries about teasing apart certain forms of speech apraxia from the language proper. 2. The preponderance of the word FACULTY at the time Broca was writing was due to the de- velopment of the so-called faculty psychology of the eighteenth-century Scottish philoso- phers Thomas Reid and Dugald Stewart. Franz Gall drew heavily from the Scottish school when developing his theories of phrenological faculties. These theories subsequently in- fluenced Bouillaud, who passed them on to Auburtin and Broca. Thirty-five years before Broca, Bouillaud (1825) had argued (in support of Gall) that the "faculty of articulate lan- guage'" is mediated in the anterior lobes of the brain (Young, 1990). 272 Hugh W. Buckingham, Jr. Benton and Joynt (1960) documented historical observations of speech- specific lingual incoordination secondary to brain damage and found that it is a long-observed phenomenon. The same observation was made by Auburtin and Bouillaud (Stookey, 1963), both of whom were precursors of Broca (Buckingham, 1981). In addition to noting simply that patients could swallow, masticate, and so forth, but could not utter words normally, Bail- larger (Alajouanine, 1960) and Auburtin (1861) observed that patients could quite fluently produce speech automatisms. Still, a third observation of the Broca's aphasic was made. Broca wrote, "that they can immediately WHEN BEING ASKED bring their tongue up, down, right, etc. But, however precise these movements may appear to us they are infinitely less so than the excessively delicate movements which the language demands" (p. 54, emphasis added). From the description provided by Broca, we have aprax- ia of speech without oral-facial apraxia (at least no involvement of the tongue). A fourth description added a "nonprotrusion" of the tongue upon VER- BAL request. J. Jackson (1866/1931a) wrote, In some cases of defect of speech the patient seems to have lost much of his pow- er to do anything he is told to, even with those muscles that are not paralyzed. Thus, a patient will be unable to put out his tongue when we ask him, although he will use it well in semi-involuntary actions, e.g. eating and swallowing. (p. 131) He added, "He will not make the particular grimace he is told to, even when we make one for him to imitate" (p. 121). Twelve years later, Jackson (1878 / 1931d) again wrote, "It will have been noticed by every medical man that some patients who have loss or defect of speech do not put out the tongue when they are asked" (p.