Prácticas de la Programación Extrema

Section 5.1.0. asked four questions. Works reported and inferences from these have given some answers.

Motorically in AS there appears to be no loss of primary sensorimotor functions. Problems multiply for the dyspraxic when primary functions have to be coordinated or phased correctly in the production of a given movement/sound. Irrespective of which coupling or phasing was examined this same underlying difficulty emerged. It affects both segmental and suprasegmental aspects of speech. The problems were placed firmly in the field of motor control. The difficulties are manifest on both phonemic and non-phonemic aspects of speech. Importantly, measures reveal the disruptions even in perceptually acceptable utterances. They are independent of language specific phonology.

What is not settled is what is explicitly programmed in motor planning and which control parameters are impaired. This issue is taken up again in the next two chapters.

How does underlying motor impairment relate to perceived sound errors? There is no straightforward mapping between physical and perceptual features, but it was argued how a large percentage of AS errors can be directly linked to phasing aberrations as component movements become progressively desynchronised.

Some error types are not accounted for by the physical studies - in particular displacements and apparent semantic- lexical intrusions.

The underlying interpretation adopted was also able to explain length and complexity effects, struggle types and sources of consistency of error locus with variability of error type.

AS was shown to have some unique and some shared characteristics vis a vis other pronunciation disorders.

These do not necessarily indicate a common aetiology. It was explained how multiple underlying disruptions may produce the same motor and sound effect - e.g. the several causes of slowing or f ricativisation.

It sometimes remains unclear how to separate (by physical measurements) aberrations due to disturbance in "programming" versus due to faulty instantiation of "programmes". This is especially true in ataxia versus AS owing to the intimate relationship of cerebral cortex and cerebellum in timing and force control, and even, some workers venture, a planning role of the cerebellum.

The finding of motor disruption in PP has theoretical implications. It prompts a reconsideration of the phonological-motor dichotomy previously assumed to underly PP versus AS, and challenges linguistic motions of how to divide phonemics from phonetics. These questions are approached again in the following chapters.

Other theoretical issues involved the segmentation problem, the notion of speech as dynamic not static, effects of motor equivalence and the relationship of different stages/phases in the microgenesis of movement that have implications for models of speech motor control.

Finally, there were implications for developing a clinical assessment. Some of these were covered in considering the correspondence between movement breakdown and perceptual outcome. Further implications include confirmation that AS is a speech disorder in its own right, is a higher (cortical) motor disorder, but that no one feature distinguishes it from neighbouring disorders. This implies that a profile of behaviours across subtests, items and error types is required to separate disorders; one cannot rely on mutually exclusive characteristics.

5.8.2. Caveats. To some it is tempting to assume that computer printouts of hard instrumental data must be more objective than ear of the listener judgements. To a degree this is

true. However, each instrumental technique has its own limitations. None gives complete detail of what is happening in speech production. Informed inferences are still required. Decisions on what to measure in the first place, what to look at to detect it, how to interpret data, all involve subjective judgements. Work is open to instrumental, theoretical, and eye-of-the-worker filters as much as perceptual work is open to ear of the listener filters. The experimental populations are open to the same biases discussed in Chapter 3. Inspection of results also reveals the same conflicting individual versus group tensions that dog generalisations from perceptual studies.

These caveats notwithstanding, physical measurements have been able to advance our understanding of what AS is and enhance our ideas of what should go forward into a clinical assessment.

Parallels to Pronunciation Disorders in Other Areas of Action

6.1. Examination of the traditional tripartite divide between the dysarthrias, AS and PP, raised several issues about if, where and how the division might fall. Conclusions suggested a reconsideration of what is actually controlled in speech motor production and the relationship between posited elements. Greater transparency in these issues is required if assessment techniques are to be based on more valid and reliable notions.

So far I have confined remarks on possible directions of search to the speech motor domain. However, it appears that observations from other areas of normal and disordered action control may help to address the problems. This chapter looks at some of these other areas to see what light they might throw on unresolved issues in the characterisation of speech motor disorders and their underlying causes.

The traditional claim is that the division phonetic-phonemic, seen as synonymous with AS versus paraphasia, rests on a dichotomy between motor and language functions. However, the same movement and derailment characteristics used to distinguish the two (AS - PP; motor-language) actually occur in all aspects of normal and disordered action. This suggests that the dichotomy is but the manifestation in speech of something fundamental to all action or movement control, and to view the supposed contrast as an argument between where motor ends and language begins is a narrow parochial perspective which misses important generalisations and insights from other fields of study. Some of these other areas are now looked at and some conclusions drawn pertinent to the relationship between pronunciation disorders preparatory to examining motor production models in Chapter 7.

6.2. As one amongst many dyspraxias, it would not be surprising to find parallels between speech and other dyspraxias. Mateer and Kimura (1977), Kimura (1982), Kimura and Watson (1989) and others (Luria 1947/1970, Brown 1977, Watamori, Itoh,

Fukusako, Sasanuma et al 1981) have reported in oral non­ verbal (buccofacial) dyspraxia the existence of two sub- types. One they describe as dysfluent with struggles to realise isolated postures, and frequently associated with tonic perseveration. It contrasts with a fluent disorder where individual postures are realised as in normals, though there may be apparent frank substitutions. Difficulties here are exposed especially on sequential tasks, where displacements and parapraxic derailments occur.

In limb dyspraxia, since the papers of Liepmarm (1900 et seq) workers have spoken of ideational versus ideomotor dyspraxia (e.g. Luria 1947/1970; Pieczuro, Vignolo 1967; Brown 1977; DeRenzi, Motti, Nichelli 1980; Poeck, Lehmkuhl 1980; Miller 1986; DeRenzi and Luchelli 1989 ; Square-Storer et al 1989). The former is seen as a fluent performance breakdown where major constituents of the action are replaced, misplaced or blended, resulting in seemingly bizarre, sometimes *jargon*, (i.e. unrecognisable as the target) and parapraxic behaviour. The classic example is the person who puts the match in their mouth and tries to strike the candle on the matchbox. Ideomotor dyspraxics on the other hand preserve the order and relationships of the action constituents, but evidence difficulty in the coordination necessary to proceed smoothly from one posture to another (i.e. transitionalisation difficulty), or they execute a recognisable posture, but with distortions in the finer detail, unrelated to physical power, tone, or coordination difficulties - e.g. hand arm orientation.

The same division, and arguments over where the dividing line rests, is found for constructional dyspraxia (Warrington 1969; Hartje, Kerschens teiner, Sturm 1975; Consoli 1979; DeRenzi 1982; Miller 1986). A fluent performance with addition, omission, substitution and displacement of parts, loss of spatial relationships, fragmentation of the whole is alleged to contrast with performance where overall Gestalt is retained, but execution is non-fluent and effortful, with difficulties (re)producing precise angles, simplication and schematicisation of the model etc.

Speech dyspraxia shares more with limb and constructional dyspraxias than the contrasts alluded to here. In these other dyspraxias one can also observe trial and error struggle, islands of fluency, inconsistency of errors, variation along the automatic-volitional continuum; and elements of length, complexity, familiarity and sense- nonsense effects. Furthermore, there are parallels in the effects of spontaneous versus imitative performance, executing tasks in isolation versus in context and of certain types of cueing.

6.3.1. It is not only in brain-damaged individuals that the fluent versus non-fluent, overall framework versus local transitions, parapraxic versus distorted contrast can be observed. It is present in healthy subjects too. Norman (1981); Reason, Mycielska (1982); Roy (1982); amongst others have noted behaviours similar to dyspraxics in normal slips of the hand and tongue (blackbird -> blackblird; bought a new cat -> caught a new bat).

Parallels between normal slips of the tongue and phonemic paraphasias have been drawn as well as inferences about mechanisms and units of control from patterns of slips (Buckingham 1986; Shattuck-Hufnagel 1987). Shattuck-Hafnagel (1987) showed though (4.3.) that there are influences on normal slips that render the relationship to pathological speech not so simple as first assumed. Dressier, Tonelli and Galdognetto (1990) found differences in patterns of slips and repairs across languages, and like Kohn (1989), asymmetries between these patterns in paraphasic versus normal speech, again stressing the non-straightforwardness of comparisons.

The transitionalisation derailments heard in AS are not reported for normals. This must rest heavily on the

influence of categorical perception. Moore et al (1988); Bizzi and Mussa-Ivaldi (1989); Forrest et al (1990) attest to there being the same kind of underlying motor activity in normals that is associated with transitionalisation problems in AS.

6.3.2. The performance of skilled copy typists is closely related to speech skills. Bimanual output of approximately five hundred key strokes per minute without visual feedback is not unlike the goal of imitative speech output in producing several hundred segments per minute.

Numerous workers (Shaffer 1978; Centner, Grudin and Conway 1980; Crudin 1983; Viviani, Terzuolo 1983; Salthouse 1986), have looked at how typists execute this highly skilled task, what variables of input (amount allowed to read ahead; coherent versus random text; real versus nonsense words etc) and output affect their performance and what slips of the hand arise. Centner et al demonstrated how, as in speech, there is look ahead, at around eight-nine characters; for 21% of keystrokes movements did not begin in the ultimate order of production; it was extremely difficult to isolate the onset and offset of individual strokes (finger movement was described as ' sea grass weaving in the waves ' ) ; and there is motor equivalence - the pattern of movement to hit a

particular key is not invariant, but the goal is.

Crudin found substitutions, omissions, additions and displacements. These arose from selecting a wrong letter, wrong finger or finger position, and wrong hand, e.g. correct finger but wrong hand; correct finger but oriented to wrong row; correct hand but wrong finger. Note, as with the vocal tract there is only a finite number of ways in which this system can fail. Less skilled typists display the same dysfluencies as speech dyspraxics, and the same inability to increase speed. Skilled typists working deliberately slowly echo the findings of Story et al (1987) in normal slow speech. Self-correcting produced the same struggle behaviours as in AS and PP.

Furthermore, transcript content influences execution. Coherent text is easiest (fewest errors, fastest time), random real-word lists are either the same or a little slower, but lists of exclusively nonsense words or real and nonsense words reduces speed by up to fifty percent. Timing and rhythm are also influenced by context - Shaffer (1978)

observed how the sequence whi was executed differently according to whether it was part of the word whig or whim.

MacNeilage (1985) concluded that similar types of error occur in typing and speech, but the constraints on occurrence are different. In speech the syllable serves as a frame, while in typing the word (Viviani et al 1983) or other unit of action organisation (Shaffer 1978; Grudin 1983) may be involved.

McNeilage's conclusions do not alter the contention that two inter-related types of action control appear to be at work. One can be described at present for the sake of argument, as acting on relatively large chunks of text/action. The other operates on a more local basis regulating force and relative speed and ironing out local perturbations. When this motor task is tapped for the purpose of typing language it is influenced by certain linguistic parameters. Though error types may reflect some linguistic derailments (misreading of a word, switching of subject and object nouns etc), to describe (and ultimately explain) slips of the hand the grammar of arm, hand and finger action is vital.

6.3.3. Maybe even closer to speech in motor terms is piano playing. It not only involves highly skilled, fine movements performed (by accomplished players) without visual feedback, but contains the paralinguis tic variations present in speech - such as variations in speed, loudness, emotive expression.

The art and science of the pianist have received attention from Shaffer (1981), Sloboda (1983), Johnson-Laird (1987). Attention has focussed on bimanual coordination and uncoupling, time and force control, effects of the player's 'knowledge* of the music genre on sight read performance and improvisation, and other issues. Of interest to the current discussion are the elements or processes of motor control derived from such studies and the nature of errors.

The former issues will be taken up again in Chapter 7 with only brief mention here. Suffice it to say that all workers

have postulated that there must be one control aspect that organises larger chunks of output (e.g. a musical phrase over several bars) within the style and speed of the piece, while another aspect involves more local changes such as progressing from chord to chord, independent control of the fingers etc.

Like typing and like speech there is read-ahead, movements for a later note are already being set up in arm, hand and finger postures before or while previous ones are being played. Skilled performers do not proceed on a note by note or chord by chord basis.

Slips of the finger/hand reveal characteristic derailments. One type involves playing wrong notes, either adding, substituting or omitting. However, harmonic structure and rhythm were maintained, i.e. at the level of the phrase overall adjustments were made to other note values to accommodate the rhythmic change, and added notes did not result in discords. These contrasted with errors arising from neighbourhood disruption to finger movements, where the correct target was being aimed for, but the finger hit a neighbouring note or force was inappropriate. These resulted in harmonic clashes or out of tone expression. The comparison with phonotactically accommodated PP but distorted AS is again invited.

6.4. Another source of comparisons for pronunciation breakdown is people who have grown up with manual signing as their sole means of communication and then become * dysphasic* following brain damage - dysphasic signers.

If the characteristics of AS are specific to breakdown in phonological and phonetic processes, the structure of a language*s phonology and movement parameters associated with properties of the vocal tract, then one would expect quite different types and loci of errors in dys^jiasic/dyspraxic signers.

This proves not to be the case. Despite having acquired and used language via completely different modalities and expression taking place within a spatial and temporal framework entirely different from speech, close correspondences are found between signing errors in 'dysphasic' signers and pronunciation breakdown, Poizner, Klima and Bellugi (1987) have studied healthy and neurologically impaired signers extensively. Findings from their studies address the present discussion.

In the same way that there can be dissociation between oral non-verbal dyspraxia and AS, so Poizner et al found that the presence of non-signing limb dyspraxia did not correlate with the presence or degree of communicative signing dyspraxia. Of course, as with the apparent oral-speech dissociation this begs the question of whether the signing-non-signing distinction rests only on the different levels of complexity of tasks administered or whether the separation does relate to the conceptual framework and goal of the action.

The signing derailments did not relate to breakdown found in body-schema disorders, spatial disorientation, and hemi- inattention or neglect as one might suspect for movement centred on personal space. There were patients with these problems, but they were dissociated from their signing skills suggesting that the internal representation or active instantiation for the two uses of space are basically different,

In signing breakdown derailments and errors found were closely akin to the picture described in typing, piano playing, handwriting, and, AS and PP, Their patient Karen L signed fluently and grammatically, but she committed 'sublexical' errors equivalent to PP in speech. For instance she substituted hand configurations, movement patterns (up and down for circular; contact for downward brushing etc) and place of articulation (e,g, chin for cheek),

Karen L displayed performance reminiscent of conduction dysphasics. Her spontaneous signing, though peppered with

conduites d ’approche, circumlocutions and apparent word finding difficulty, was largely error free and functionally adequate. On repetition of individual signs and sentences she coped with short sequences of three or four signs, but as stimuli increased in length and complexity, struggle behaviour increased and her productions were full of transpositions, omissions and additions, which involved sub­ elements of signs, not random movements from outside of her sign system. The derailments were incorporated fluently into her responses.

In contrast Gail D initially evidenced ideational dyspraxia in her non-signing lin±> movements (used fork wrong way round etc) and was ’mute’ communicatively. As she gradually regained her signing it was characterised by effortful trial and error groping for correct postures. Syntax was highly underspecifled, with omissions of morphological markers, derivational affixes, sign order breakdown, all reminiscent of agrammatic dysphasics. To compensate for this she resorted to non-signing gestures and finger spelling. The comparison with Broca’s dysphasics who resort to gesture and writing is not unwarranted.

Even more significantly, however, in drawing parallels between signing and speaking dysphasic-dyspraxics, Gail D showed instances of the inconsistency, automaticity, struggle, distortions and comnunicative mode effects common to AS. A given sign would be preceded by homing-in struggle, and distorted but recognisable sign elements on one occasion, but be fluently, effortlessly produced on another. She produced a sub-element of a sign correctly in one sign, derailed in another. Other times a sub-element, e.g. path movement of hand towards body in the sign for accept - would be correctly executed, but omitted or distorted when the same gesture served as an inflectional morpheme.

More interestingly, in resorting to finger spelling Gail D was able to use movements more complex than those required to