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The Edinburgh Disfluency Group Researching disfluency from a psycholinguistic perspective: Language.

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Presentation on theme: "The Edinburgh Disfluency Group Researching disfluency from a psycholinguistic perspective: Language."— Presentation transcript:

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2 The Edinburgh Disfluency Group Researching disfluency from a psycholinguistic perspective: Language and speech encoding – Grammar – Phonology – Phonetics A general interest in – Speech errors – Speech-error repair and avoidance mechanisms

3 Stuttering and the Dysarthrias Paul Brocklehurst University of Edinburgh June 2011 Talk for Scottish dysfluency SIG Funded by The Economic and Social Research Council

4 Stuttering and the dysarthrias Historical perspective: – Robert West, 1929 Evidence for underlying speech motor control deficit – The ‘fluent’ speech of stutterers: perceptual and acoustic evaluations PWS’ control of non-speech movements Is stuttering more common in people with dysarthria? – Types of dysarthria most strongly associated with stuttering Is stuttering a response to an underlying deficit? – Adaptation theory Possible relevance of theory to therapy – The “not good enough” hypothesis – Lessons learned from getting drunk – Identifying an optimal speaking strategy

5 West (1929) “A neurological test for stutterers” Compared to controls, PWS are slower at operating a morse key with their lips. 25 PWS 39 controls

6 West (1929) “A neurological test for stutterers”

7 Diadochokinetic rates in PWS more recent evidence – not so convincing PWS slower than controls Cross (1936) PWS not different to controls Spriestersbach (1940) Strother & Kriegman (1943) Chworowski (1952) Wolk Edwards & Conture (1993) - Children Yaruss Logan & Conture (1995) - Children

8 The Fluent speech of PWS - Listener Perceptions Listeners can tell it’s not normal Wendahl & Cole (1961) “more force and strain” Brown & Colcord (1987 ) – (adolescents), easy to discriminate Few & Lingwall (1972 ) – inconclusive, but PWS rated as “slower” Howell & Wingfield (1990 ) – segments adjacent to stuttered words easy to discriminate Lickley et al (2005 ) – PWS rated as more disfluent Listeners cannot tell the difference Young (1964) Krikorian and Runyan (1983) – (4-6 year olds) trained judges

9 The Fluent speech of PWS - cinematic analyses PWS’ ‘fluent’ speech is characterised by.... Slowness Late onsets More limited movements More variable movements Poor coordination of larynx and articulators ( summary from Bloodstein & Ratner 2008)

10 The Fluent speech of PWS - instrumental analyses PWS’ ‘fluent’ speech is characterised by.... Slowness Late onsets More limited movements More variable movements Poor coordination of larynx and articulators Are these differences... Symptoms of adaptation (due to anticipation of difficulty) ? Symptoms of underlying impairment of speech motor control?

11 Non-speech tasks: fine movement control of the articulators in PWS Coarser movements of the jaw, tongue and lower lip compared to normal speakers (DeNil & Abbs 1991) Higher error and variability levels than controls... – on jaw-movement accuracy tasks (Loucks & DeNil 1996) – On non-speech jaw-phonatory coordination. (Loucks DeNil & Sasisekaran 2007) Longer durations and greater displacements when making fine muscle movements. (Max Caruso & Gracco, 2003) – Mainly lips and jaw – Hand movements also affected

12 Finger and hand movements motor control and timing Differences between PWS and controls emerge with more difficult tasks. Bimanual finger/hand tapping to a metronome beat – PWS are poorer time-keepers. Adults: (Hulstijn, Summers, van Lieshout, & Peters, 1992) Children: (Olander Smith & Zelaznik, 2010). Finger flexion to a metronome beat – PWS move with less amplitude and peak velocity and exhibit greater relative phase variability (Zelaznik, Smith, Franz, & Ho, 1997)

13 Finger flexion to a metronome beat in Adults who stutter. – PWS move with less amplitude and peak velocity and exhibit greater relative phase variability (Zelaznik, Smith, Franz, & Ho, 1997)

14 Proprioception in PWS reduced reliance on proprioception in PWS – PWS benefit more when visual feedback is available. (minimal displacement paradigm, De Nil & Abbs 1991, Howell Sackin & Rustin 1995) poorer proprioception in PWS – PWS have reduced undershoot with tendon-vibration, (Loucks & De Nil 2006)

15 From DeNil & Abbs 1991 Compared to non-stuttering controls, their movements, on average, were twice as imprecise. The ability to make small movements was significantly correlated with stuttering severity

16 Speech motor control and stuttering In summary... Strong evidence, in PWS, of – impaired fine motor control – impaired proprioception – Impaired motor learning The abnormalities found in perceptually-fluent speech of PWS probably, at least in part, reflect an underlying impairment of speech motor control.

17 Dysarthria… A collective name for a group of motor speech disorders associated with disturbed muscular execution or control of the speech mechanism due to CNS and/or PNS damage. May include abnormalities in strength, speed, range, tone or accuracy of speech movements. May affect respiration, phonation, resonance, articulation, & prosody. (Duffy 2005)

18 Dysarthria Types (Duffy 2005) TypeLocusPrimary Deficit FlaccidLower motor neuronsWeakness SpasticUpper motor neuronsSpasticity HypokineticBasal ganglia control circuitRigidity, distorted sensory awareness HyperkineticBasal ganglia control circuitInvoluntary movements AtaxicCerebellar control circuitIncoordination Unilateral UMN Weakness; spasticity MixedMore than one

19 Dysarthria Types (Duffy 2005) TypeLocusPrimary Deficit FlaccidLower motor neuronsWeakness SpasticUpper motor neuronsSpasticity HypokineticBasal ganglia control circuitRigidity, distorted sensory awareness HyperkineticBasal ganglia control circuitInvoluntary movements AtaxicCerebellar control circuitIncoordination Unilateral UMN Weakness; spasticity MixedMore than one

20 Hypokinetic Dysarthria – Etiologies (Duffy 2005) e.g. Parkinson’s Disease

21 Hypokinetic Dysarthria failure of the basal ganglia control-circuit to provide background support for voluntary neuromuscular activity The basal ganglia control-circuit General Functions – Regulates muscle tone – Regulates movements that support goal-directed activities (e.g. arm- swing during walking & postural adjustments during skilled movements) – Assists in the learning, selection and initiation of movements. Speech-related functions – Damps/modulates cortical output – Maintains stable musculoskeletal environment for articulation

22 Hypokinetic Dysarthria Most commonly seen in Parkinson’s patients, of which… – 89% have voice abnormalities – 45% have articulation difficulty – 20% have rate abnormalities including… Phoneme and syllable repetitions (at start of words) Shortened syllables Prolongations (both vowels and consonents) Excessive pauses – 10% are hypernasal

23 Hypokinetic Dysarthria sensory deficits – Reduced proprioceptive/kinaesthetic awareness – Poor temporal and spatial discrimination – Difficulty estimating movement displacement – Lack of awareness of loudness of speech – Much of the therapy aimed at “recalibration” of internal models… E.g. LSVT, Loud speech, Clear speech.

24 Hypokinetic dysarthria – patient perceptions Patients complain that others tell them their voice is – quieter – Weaker – Too fast – Too indistinct They often deny that it is true They often use the word ‘stutter’ to describe the experiences of… – Difficulty ‘getting speech started’ – sound, syllable and word repetitions – But not preceded by premonition of difficulty (unlike stuttering)

25 Stuttering following L-dopa medication for Parkinson’s Disease (Anderson et al 1999) Patient (M,44) asked to tell fairy stories. %SS rated by 2 raters, blinded to the conditions. See also Koller (1983) - severe worsening during “on” periods in case 3.

26 Hypokinetic dysarthria – Conclusions Disfluencies characteristically associated with Parkinson’s disease have some superficial resemblances to stuttering. Alm’s (2004) Dual-Premotor theory posits similar mechanisms. However, the subjective experience appears to be different… – Parkinson’s patients benefit from learning to consciously control aspects of speech that would normally be automatic. – stuttering becomes worse if PWS attempt the same sort of conscious control Return of childhood stuttering in Parkinson’s disease may be associated with use of L-dopa medication.

27 Hyperkinetic Dysarthrias - Too Much Movement The basal ganglia have two functions… 1.They provide the necessary background muscle tone upon which supports voluntary actions – cortical output 2.In conjunction with the Cerebellum, they inhibit unwanted cortical output. In Hyperkinetic dysarthrias, there is a loss of this inhibition.

28 Hyperkinetic Dysarthrias – Etiologies (Duffy 2005) Antipsychotic drugs Large genetic/ hereditary component e.g. Huntington’s disease

29 Hyperkinetic Dysarthrias – Athetosis (slow writhing movements) e.g. Cerebral Palsy – Tics (stereotypical co-ordinated movements under partial voluntary control) e.g. Tourettes Syndrome – Chorea (rapid non-stereotypic body-part movement) – Tremor – Dystonias (slow, excessive contraction of antagonists) e.g. Spasmodic Dysphonia – Myoclonus (involuntary “lightening-like” jerks) – Dyskinesias (e.g. tardive dyskinesia)

30 Stuttering and Cerebral Palsy Paine (1962) – found stuttering in 7 out of 78 CP children ≈ 9% prevalence. All were over 14 years. Type of CP was not specified. Rutherford (1939) reviewed 32 children with athetotic and 27 with spastic CP. – 3 out of 32 with athetotic CP stuttered (and a further 3 had previously stuttered) ≈ 10% +10% – 0 out of 27 with spastic CP stuttered (one had previously) 0% +3% Numbers too low to be certain, but suggestive that stuttering is associated with athetotic CP... Not spastic CP

31 Laryngeal tension in PWS (Smith et al. 1996) AWS have a lower thyroarytenoid and cricothyroid operating range during conversational speech, AWS’ disfluencies did not produce relatively high activation levels. Smith et al. reject the claim that adults with a history of chronic stuttering routinely produce excessive levels of intrinsic laryngeal muscle activity.

32 Stuttering and Tourettes syndrome (Ludlow & Loucks, 2003) 45% of people with TS report having stuttered as a child (Ludlow 1993) (also co-occurs with ADHD, dyslexia, OCD) TS and stuttering often found in the same family. Both conditions improved by dopamine blockers. Symptoms are intermittent – remission and relapse the norm. Mostly males (3:1 ratio) Symptoms in both conditions preceded by premonition

33 Ataxia: impairment of the cerebellar control circuit the cerebellum... coordinates sequences of muscle contractions for skilled motor behaviour. – times the components of movement, – scales the size of muscle actions, Integrates auditory and proprioceptive feedback (allows online corrections) Cooperates with the basal ganglia control circuit

34 Ataxia – general symptoms Incoordination Errors in speed, range, force, timing, & direction of movements Hypotonia (especially a decrease in resistance to passive movement) slow voluntary movements, Dysmetria (poor judgement of space and time) Impaired language processing (Duffy,2005, p166)

35 Ataxic Dysarthria Most evident in Articulation and Prosody – Imprecise articulation, dysprosody, Irregular articulatory breakdowns, Inappropriate silences Slow rate vowel distortions, excess/equal stress, excess loudness variations May sound like the speaker is drunk

36 Ataxic Dysarthria – Etiologies (Duffy 2005) Mainly hereditary e.g. MS e.g. Alcoholism, Valium use

37 Ataxia and drunkenness Alcohol temporarily impairs cerebellar function. Many symptoms of drunkenness are symptoms of ataxia. Motor performance of people with ataxia is strongly influenced by even small amounts of alcohol.

38 Stuttering and drunkenness Stuttering is – often relieved by drunkenness – Sometimes exacerbated by drunkenness Two factors – Poorer speech quality (ataxic dysarthria) – Less concern/awareness about speech quality

39 Stuttering - a maladaptive response to an underlying deficit? It seems that the relationship between stuttering and dysarthria is not straight forward... Many people with severe dysarthria do not stutter. Stuttering fluctuates... And is strongly influenced by the speaker’s perceptions of the speaking situation. Rather than being the immediate consequences of dysarthria. stuttering-like disfluencies may be the symptoms of stutterers’ attempts to avoid the symptoms of dysarthria.

40 Stuttering and the dysarthrias Conclusions At least some people who stutter have underlying impairments of – fine motor control – Proprioception They may have mild hyperkinetic or ataxic dysarthria In those people, most likely, stuttering is a symptom of adaptation to those underlying impairments A symptom of trying to speak more clearly/accurately than they are really able.

41 Stuttering and the dysarthrias Conclusions Perhaps different impairments underlie stuttering in different PWS. In some it may be dysarthria, In others, there may be an underlying language-formulation, or motor-programming deficit. Whatever the case, the net result is a relatively poor quality of speech. But it is likely that stuttering only arises when they make a conscious effort to speak ‘better’.

42 Stuttering and the dysarthrias further thoughts PWS are faced with having to make a trade-off Fluency vs Accuracy Choosing accuracy results in stuttering – Lots of disfluencies Choosing fluency results in poorer speech quality – Less precise articulation, – more speech errors For each speaking situation, the needs are different. – But it is likely that, in many situations, PWS would benefit if they paid less attention to accuracy and more attention to fluency.

43 Thank you

44 The Edinburgh Disfluency Group References


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