DISCUSIÓN

In the years since Darley (1968) first described apraxia of speech (AOS) as an articulatory programming disorder that could not be accounted for by disrupted linguistic or fundamental motor processes, considerable work has been done to elucidate the perceptual, acoustic, kine-matic, aerodynamic, and electromyographic features that characterize AOS (cf. McNeil, Robin, and Schmidt, 1997; McNeil, Doyle, and Wambaugh, 2000). Explana-tory models consistent with these observations have been proposed (Van der Merwe, 1997).

Overwhelmingly, the evidence supports a conceptual-ization of AOS as a

neurogenic speech disorder caused by ine‰ciencies in the spec-ification of intended articulatory movement parameters or motor programs which result in intra- and interarticulator temporal and spatial segmental and prosodic distortions. Such movement distortions are realized as extended segmental, in-tersegmental transitionalization, syllable and word durations, and are frequently perceived as sound substitutions, the mis-assignment of stress, and other phrasal and sentence-level prosodic abnormalities. (McNeil, Robin, and Schmidt, 1997, p. 329)

Traditional and contemporary conceptualizations of the disorder have resulted in specific assumptions re-garding appropriate tactics and targets of intervention, and a number of treatment approaches have been pro-posed that seek to enhance (1) postural shaping and

phasing of the articulators at the segmental and syllable levels, and (2) segmental sequencing of longer speech units (Square-Storer and Hayden, 1989).

More recently, arguments supporting the application of motor learning principles (Schmidt, 1988) for the purposes of specifying the structure of AOS treatment sessions have been proposed, based on evidence that such principles facilitate learning and retention of motor routines involved in skilled limb movements (Schmidt, 1991). The empirical support for each approach to treatment is reviewed here.

Enhancing Articulatory Kinematics at the Segmental Level. Several facilitative techniques have been recom-mended to enhance postural shaping and phasing of the articulators at the segmental and syllable levels and have been described in detail by Wertz, LaPointe, and Rosen-bek (1984). These techniques include (1) phonetic deri-vation, which refers to the shaping of speech sounds based on corresponding nonspeech postures, (2) pro-gressive approximation, which involves the gradual shaping of targeted speech segments from other speech segments, (3) integral stimulation and phonetic placement, which employ visual models, verbal descriptions and physical manipulations to achieve the desired articu-latory posture, and movement, and (4) minimal pairs contrasts, which requires patients to produce syllable or word pairs in which one member of the pair di¤ers min-imally with respect to manner, place, or voicing features from the other member of the pair.

Several early studies examined, in isolation or in various combinations, the e¤ects of these facilitative techniques on speech production, and reported positive treatment responses (Rosenbek et al., 1973; Holtzapple and Marshall, 1977; Deal and Florance, 1978; Thomp-son and Young, 1983; LaPointe, 1984; Wertz, 1984).

However, most of these studies su¤ered from method-ological limitations, including inadequate subject selec-tion criteria, nonreplicable treatment protocols, and pre-experimental research designs, which precluded firm conclusions regarding the validity and generalizability of the reported treatment e¤ects. Contemporary investiga-tions have addressed these methodological shortcomings and support earlier findings regarding the positive e¤ects of treatment techniques aimed at enhancing articulatory kinematic aspects of speech at the sound, syllable, and word levels.

Specifically, in a series of investigations using single-subject experimental designs Wambaugh and colleagues examined the e¤ects of a procedurally explicit treatment protocol employing the facilitative techniques of integral stimulation, phonetic placement, and minimal pair con-trasts in 11 well-described subjects with AOS (Wam-baugh et al., 1996, 1998, 1999; Wam(Wam-baugh, West, and Doyle, 1998; Wambaugh and Cort, 1998; Wambaugh, 2000). These studies revealed positive treatment e¤ects on targeted phonemes in trained and untrained words for all subjects across all studies, and positive main-tenance e¤ects of targeted sounds at 6 weeks post-treatment. In addition, two subjects showed positive

generalization of trained sounds to novel stimulus con-texts (i.e., untrained phrases), and one subject showed positive generalization to untrained sounds within the same sound class (voiced stops). These results provide initial experimental evidence that treatment strategies designed to enhance postural shaping and phasing of the articulators are e‰cacious in improving sound production of treated and untreated words. Further, there is limited evidence that for some patients and some sounds, generalization to untrained contexts may be expected.

Enhancing Segmental Sequencing of Longer Speech Units. Several facilitative techniques have been recom-mended to improve speech production in persons with AOS, based on the premise that the sequencing and co-ordination of movement parameters required for the production of longer speech units (and other complex motor behaviors) are governed by internal oscillatory mechanisms (Gracco, 1990) and temporal constraints (Kent and Adams, 1989). Treatment programs and tac-tics grounded in this framework employ techniques designed to reduce or control speech rate while enhanc-ing the natural rhythm and stress contours of the tar-geted speech unit. The e¤ects of several such specific facilitative techniques have been studied. These include metronomic pacing (Shane and Darley, 1978; Dworkin, Abkarian, and Johns, 1988; Dworkin and Abkarian, 1996; Wambaugh and Martinez, 1999), prolonged speech (Southwood, 1987), vibrotactile stimulation (Rubow et al., 1982), and intersystemic facilitation (i.e., finger counting) (Simmons, 1978). In addition, the e¤ects of similarly motivated treatment programs, melodic in-tonation therapy (Sparks, 2001) and surface prompts (Square, Chumpelik, and Adams, 1985), have also been reported.

As with studies examining the e¤ects of techniques designed to enhance articulatory kinematic aspects of speech at the segmental level, the empirical evidence supporting the facilitative e¤ects of rhythmic pacing, rate control, and stress manipulations on the production of longer speech units in adults with AOS is limited.

That is, among the reports cited, only five subjects were studied under conditions that permit valid conclusions to be drawn regarding the relationship between applica-tion of the facilitative technique and the dependent measures reported (Southwood, 1987; Dworkin et al., 1988; Dworkin and Abkarian, 1996; Wambaugh et al., 1999). Whereas each of these studies reported positive results, it is di‰cult to compare them because of di¤er-ences in the severity of the disorder, in the frequency, duration, and context in which the various facilitative techniques were applied, in the behaviors targeted for intervention, and in the extent to which important aspects of treatment e¤ectiveness (i.e., generalized e¤ects) were evaluated. As such, the limited available evidence suggests that techniques that reduce the rate of articulatory movements and highlight rhythmic and prosodic aspects of speech production may be e‰cacious in improving segmental coordination in longer speech

units. However, until these findings can be systematically replicated, their generalizability remains unknown.

General Principles of Motor Learning. The contempo-rary explication of AOS as a disorder of motor planning and programming has given rise to a call for the appli-cation of motor learning principles in the treatment of AOS (McNeil et al., 1997, 2000; Ballard, 2001). The habituation, transfer, and retention of skilled movements (i.e., motor learning) and their controlling variables have been studied extensively in limb systems from the per-spective of schema theory (Schmidt, 1975). This research has led to the specification of several principles regarding the structure of practice and feedback that were found to enhance retention of skilled limb movements post-treatment, and greater transfer of treatment e¤ects to novel movements (Schmidt, 1991). Three such principles are particularly relevant to the treatment of AOS: (1) the need for intensive and repeated practice of the targeted skilled movements, (2) the order in which targeted movements are practiced, and (3) the nature and sched-ule of feedback.

With respect to the first of these principles, clinical management of AOS has long espoused intensive drill of targeted speech behaviors (Rosenbek, 1978; Wertz et al., 1984). However, no studies have examined the e¤ects of manipulating the number of treatment trials on the ac-quisition and retention of speech targets in AOS, and little attention has been paid to the structure of drills used in treatment. That is, research on motor learning in limb systems has shown that practicing several di¤er-ent skilled actions in random order within training ses-sions facilitates greater retention and transfer of targeted actions than does blocked practice of skilled movements (Schmidt, 1991). This finding has been replicated by Knock et al. (2000) in two adult subjects with AOS in the only study to date to experimentally manipulate random versus blocked practice to examine acquisition, retention, and transfer of speech movements.

The final principle to be discussed concerns the nature and schedule of feedback employed in the training of skilled movements. Two types of feedback have been studied, knowledge of results (KR) and knowledge of performance (KP). KR provides information only with respect to whether the intended movement was per-formed accurately or not. KP provides information re-garding aspects of the movement that deviate from the intended action and how the intended action is to be performed. Schmidt and Lee (1999) argue that KP is most beneficial during the early stages of training but that KR administered at low response frequencies pro-motes greater retention of skilled movements. Both types of feedback are frequently employed in the treatment of AOS. Indeed, the facilitative techniques of integral stimulation and phonetic placement provide the type of information that is consistent with the concept of KP. However, these facilitative techniques are most fre-quently used as antecedent conditions to enhance target performance, and response-contingent feedback fre-quently takes the form of KR. The e¤ects of the nature, Apraxia of Speech: Treatment 105

schedule, and timing of performance feedback have not been systematically investigated in AOS.

In summary, AOS is a treatable disorder of motor planning and programming. Studies examining the ef-fects of facilitative techniques aimed at improving pos-tural shaping and phasing of the articulators at the segmental level and sequencing and coordination of seg-ments into long utterances have reported positive out-comes. These studies are in need of carefully controlled systematic replications before generalizability can be in-ferred. Further, the e¤ects of motor learning principles (Schmidt and Lee, 1999) on the habituation, mainte-nance, and transfer of speech behaviors require system-atic evaluation in persons with AOS.

—Patrick J. Doyle and Malcolm R. McNeil

References

Ballard, K. J. (2001). Principles of motor learning and treatment for AOS. Paper presented at the biennial Motor Speech Conference, Williamsburg, VA.

Darley, F. L. (1968). Apraxia of speech: 107 years of termino-logical confusion. Paper presented at the annual convention of the American Speech and Hearing Association, Denver, CO.

Deal, J. L., and Florance, C. L. (1978). Modification of the eight-step continuum for treatment of apraxia of speech in adults. Journal of Speech and Hearing Disorders, 43, 89–95.

Dworkin, J. P., and Abkarian, G. G. (1996). Treatment of phonation in a patient with apraxia and dysarthria second-ary to severe closed head injury. Journal of Medical Speech-Language Pathology, 4, 105–115.

Dworkin, J. P., Abkarian, G. G., and Johns, D. F. (1988).

Apraxia of speech: The e¤ectiveness of a treatment regime.

Journal of Speech and Hearing Disorders, 53, 280–294.

Gracco, V. L. (1990). Characteristics of speech as a motor control system. In G. E. Hammond (Ed.), Cerebral control of speech and limb movements. Amsterdam: North-Holland.

Holtzapple, P., and Marshall, N. (1977). The application of multiphonemic articulation therapy with apraxic patients.

In R. H. Brookshire (Ed.), Clinical Aphasiology Conference proceedings (pp. 46–58). Minneapolis: BRK.

Kent, R. D., and Adams, S. G. (1989). The concept and measurement of coordination in speech disorders. In S. A. Wallace (Ed.), Advances in psychology: Perspectives on the coordination of movement (pp. 415–450). New York:

Elsevier.

Knock, T. R., Ballard, K. J., Robin, D. A., and Schmidt, R.

(2000). Influence of order of stimulus presentation on speech motor learning: A principled approach to treatment for apraxia of speech. Aphasiology, 14, 653–668.

LaPointe, L. L. (1984). Sequential treatment of split lists: A case report. In J. Rosenbek, M. McNeil, and A. Aronson (Eds.), Apraxia of speech: Physiology, acoustics, linguistics, management (pp. 277–286). San Diego, CA: College-Hill Press.

McNeil, M. R., Doyle, P. J., and Wambaugh, J. (2000).

Apraxia of speech: A treatable disorder of motor planning and programming. In S. E. Nadeau, L. J. Gonzalez-Rothi, and B. Crosson (Eds.), Aphasia and language: From theory to practice (pp. 221–265). New York: Guilford Press.

McNeil, M. R., Robin, D. A., and Schmidt, R. A. (1997).

Apraxia of speech: Definition, di¤erentiation, and treat-ment. In M. R. McNeil (Ed.), Clinical management of

sen-sorimotor speech disorders (pp. 311–344). New York:

Thieme.

Rosenbek, J. C. (1978). Treating apraxia of speech. In D. F.

Johns (Ed.), Clinical Management of neurogenic communi-cative disorders (pp. 191–241). Boston: Little, Brown.

Rosenbek, J. C., Lemme, M. L., Ahern, M. B., Harris, E. H., and Wertz, R. T. (1973). A treatment for apraxia of speech in adults. Journal of Speech and Hearing Disorders, 38, 462–472.

Rubow, R. T., Rosenbek, J. C., Collins, M. J., and Longstreth, D. (1982). Vibrotactile stimulation for intersystemic re-organization in the treatment of apraxia of speech. Archives of Physical Medicine Rehabilitation, 63, 150–153.

Schmidt, R. A. (1975). A schema theory of discrete motor skill learning. Psychological Review, 82, 225–260.

Schmidt, R. A. (1988). Motor control and learning: A be-havioral emphasis (2nd ed.). Champaign, IL: Human Kinetics.

Schmidt, R. A. (1991). Frequent augmented feedback can de-grade learning: Evidence and interpretations. In R. Requin and G. E. Stelmach (Eds.), Tutorials in neuroscience. Dor-drecht: Kluwer Academic.

Schmidt, R. A., and Lee, T. D. (1999). Motor control and learning: A behavioral emphasis (3rd ed.). Champaign, IL:

Human Kinetics.

Shane, H. C., and Darley, F. L. (1978). The e¤ect of auditory rhythmic stimulation on articulatory accuracy in apraxia of speech. Cortex, 14, 444–450.

Simmons, N. N. (1978). Finger counting as an intersystemic reorganizer in apraxia of speech. In R. H. Brookshire (Ed.), Clinical Aphasiology Conference proceedings (pp. 174–179).

Minneapolis: BRK.

Southwood, H. (1987). The use of prolonged speech in the treatment of apraxia of speech. In R. H. Brookshire (Ed.), Clinical Aphasiology Conference proceedings (pp. 277–287).

Minneapolis: BRK.

Sparks, R. W. (2001). Melodic intonation therapy. In R. Cha-pey (Ed.), Language intervention strategies in adult aphasia (4th ed., pp. 703–717). Baltimore: Lippincott Williams and Wilkins.

Square, P. A., Chumpelik, D., and Adams, S. (1985). E‰cacy of the PROMPT system of therapy for the treatment of acquired apraxia of speech. In R. H. Brookshire (Ed.), Clinical Aphasiology Conference proceedings (pp. 319–320).

Minneapolis: BRK.

Square-Storer, P., and Hayden, D. C. (1989). PROMPT treat-ment. In P. Square-Storer (Ed.), Acquired apraxia of speech in aphasic adults (pp. 190–219). London: Taylor and Francis.

Thompson, C. K., and Young, E. C. (1983). A phonological process approach to apraxia of speech: An experimental analysis of cluster reduction. Paper presented at a meeting of the American Speech Language and Hearing Association, Cincinnati, OH.

Van der Merwe, A. (1997). A theoretical framework for the characterization of pathological speech sensorimotor con-trol. In McNeil (Ed.), Clinical management of sensorimotor speech disorders (pp. 1–25). New York: Thieme.

Wambaugh, J. L. (2000). Stimulus generalization e¤ects of treatment for articulatory errors in apraxia of speech. Poster session presented at the biennial Motor Speech Conference, San Antonio, TX.

Wambaugh, J. L., and Cort, R. (1998). Treatment for AOS:

Perceptual and VOT changes in sound production. Poster session presented at the biennial Motor Speech Conference, Tucson, AZ.

Wambaugh, J. L., Doyle, P. J., Kalinyak, M., and West, J.

(1996). A minimal contrast treatment for apraxia of speech.

Clinical Aphasiology, 24, 97–108.

Wambaugh, J. L., Kalinyak-Flizar, M. M., West, J. E., and Doyle, P. J. (1998). E¤ects of treatment for sound errors in apraxia of speech and aphasia. Journal of Speech Language and Hearing Research, 41, 725–743.

Wambaugh, J. L., and Martinez, A. L. (1999). E¤ects of rate and rhythm control on sound production in apraxia of speech. Aphasiology, 14, 603–617.

Wambaugh, J. L., Martinez, A. L., McNeil, M. R., and Rogers, M. (1999). Sound production treatment for apraxia of speech: Overgeneralization and maintenance e¤ects.

Aphasiology, 13, 821–837.

Wambaugh, J. L., West, J. E., and Doyle, P. J. (1998). Treat-ment for apraxia of speech: E¤ects of targeting sound groups. Aphasiology, 12, 731–743.

Wertz, R. T. (1984). Response to treatment in patients with apraxia of speech. In J. C. Rosenbek, M. R. McNeil, and A. E. Aronson (Eds.), Apraxia of speech: Physiology, acous-tics, linguisacous-tics, management (pp. 257–276). San Diego, CA:

College-Hill Press.

Wertz, R. T., LaPointe, L. L., and Rosenbek, J. C. (1984).

Apraxia of speech in adults: The disorder and its manage-ment. Orlando, FL: Grune and Stratton.

Further Readings

Dabul, B., and Bollier, B. (1976). Therapeutic approaches to apraxia. Journal of Speech and Hearing Disorders, 41, 268–276.

Freed, D. B., Marshall, R. C., and Frazier, K. E. (1977). The long-term e¤ectiveness of PROMPT treatment in a severely apractic-aphasic speaker. Aphasiology, 11, 365–372.

Florance, C. L., Rabidoux, P. L., and McCauslin, L. S. (1980).

An environmental manipulation approach to treating apraxia of speech. In R. H. Brookshire (Ed.), Clinical Aphasiology Conference proceedings (pp. 285–293). Minne-apolis: BRK.

Howard, S., and Varley, R. (1995). EPG in therapy: Using electropalatography to treat severe acquired apraxia of speech. European Journal of Disorders of Communication, 30, 246–255.

Keith, R. L., and Aronson, A. E. (1975). Singing as therapy for apraxia of speech and aphasia: Report of a case. Brain and Language, 2, 483–488.

Lane, V. W., and Samples, J. M. (1981). Facilitating commu-nication skills in adult apraxics: Application of blisssymbols in a group setting. Journal of Communication Disorders, 14, 157–167.

Lee, T. D., and Magill, R. A. (1983). The locus of contextual interference in motor-skill acquisition. Journal of Experi-mental Psychology: Learning, Memory, and Cognition, 9, 730–746.

McNeil, M. R., Prescott, T. E., and Lemme, M. L. (1976). An application of electro-myographic biofeedback to aphasia/

apraxia treatment. In R. H. Brookshire (Ed.), Clinical Aphasiology Conference proceedings (pp. 151–171). Minne-apolis: BRK.

Rabidoux, P., Florance, C., and McCauslin, L. (1980). The use of a Handi Voice in the treatment of a severely apractic nonverbal patient. In R. H. Brookshire (Ed.), Clinical Aphasiology Conference proceedings (pp. 294–301). Minne-apolis: BRK.

Raymer, A. M., and Thompson, C. K. (1991). E¤ects of verbal plus gestural treatment in a patient with aphasia and severe

apraxia of speech. In T. E. Prescott (Ed.), Clinical Aphasi-ology, 20, 285–298. Austin, TX: Pro-Ed.

Robin, D. A. (1992). Developmental apraxia of speech:

Just another motor problem. American Journal of Speech-Language Pathology: A Journal of Clinical Practice, 1, 19–22.

Schmidt, R. A., and Bjork, R. A. (1992). New conceptualiza-tions of practice: Common principles in three paradigms suggest new concepts for training. Psychological Science, 3, 207–217.

Shea, C. H., and Morgan, R. L. (1979). Contextual interfer-ence e¤ects on the acquisition retention, and transfer of a motor skill. Journal of Experimental Psychology: Human Learning and Memory, 5, 179–187.

Shea, J. B., and Wright, D. L. (1991). When forgetting benefits motor retention. Research Quarterly for Exercise and Sport, 62, 293–301.

Simmons, N. N. (1980). Choice of stimulus modes in treating apraxia of speech: A case study. In R. H. Brookshire (Ed.), Clinical Aphasiology Conference proceedings (pp. 302–307).

Minneapolis: BRK.

Square, P. A., Chumpelik, D., Morningstar, D., and Adams, S.

(1986). E‰cacy of the PROMPT system of therapy for the treatment of acquired apraxia of speech: A follow-up investigation. In R. H. Brookshire (Ed.), Clinical Aphasiol-ogy Conference proceedings (pp. 221–226). Minneapolis:

BRK.

Square-Storer, P. (1989). Traditional therapies for AOS:

Reviewed and rationalized. In P. Square-Storer (Ed.), Acquired apraxia of speech in aphasic adults. London:

Taylor and Francis.

Square-Storer, P., and Martin, R. E. (1994). The nature and treatment of neuromotor speech disorders in aphasia. In R. Chapey (Ed.), Language intervention strategies in adult aphasia (pp. 467–499). Baltimore: Williams and Wilkins.

Wambaugh, J. L., and Doyle, P. D. (1994). Treatment for acquired apraxia of speech: A review of e‰cacy reports.

Clinical Aphasiology, 22, 231–243.

Wulf, G., and Schmidt, R. A. (1994). Feedback-induced vari-ability and the learning of generalized motor programs.

Journal of Motor Behavior, 26, 348–361.

Aprosodia

Prosody consists of alterations in pitch, stress, and du-ration across words, phrases, and sentences. These same parameters are defined acoustically as fundamental fre-quency, intensity, and timing. It is the variation in these parameters that not only provides the melodic contour of speech, but also invests spoken language with linguis-tic and emotional meaning. Prosody is thus crucial to conveying and understanding communicative intent.

The term ‘‘aprosodia’’ was first used by Monrad-Krohn (1947) to describe loss of the prosodic features of speech. It resurfaced in the 1980s in the work of Ross and his colleagues to refer to the attenuated use of and decreased sensitivity to prosodic cues by right hemisphere damaged patients (Ross and Mesulam, 1979;

Ross, 1981; Gorelick and Ross, 1987).

Prosodic deficits in expression or comprehension can accompany a variety of cognitive, linguistic, and psychi-atric conditions, including dysarthria and other motor Aprosodia 107

speech disorders, aphasia, chronic alcoholism, schizo-phrenia, depression, and mania, as well as right hemi-sphere damage (RHD) (Du¤y, 1995; Myers, 1998;

Monnot, Nixon, Lovallo, and Ross, 2001). The term aprosodia, however, typically refers to the prosodic impairments that can accompany RHD from stroke, head injury, or progressive neurologic disease with a right hemisphere focus. Even the disturbed prosody of other illnesses, such as schizophrenia, may be the result of alterations in right frontal and extrapyramidal areas, areas considered important to prosodic impairment sub-sequent to RHD (Sweet, Primeau, Fichtner et al., 1998;

Monnot, Nixon, Lovallo, and Ross, 2001). The term aprosodia, however, typically refers to the prosodic impairments that can accompany RHD from stroke, head injury, or progressive neurologic disease with a right hemisphere focus. Even the disturbed prosody of other illnesses, such as schizophrenia, may be the result of alterations in right frontal and extrapyramidal areas, areas considered important to prosodic impairment sub-sequent to RHD (Sweet, Primeau, Fichtner et al., 1998;