The Edinburgh Disfluency Group
http://edgwiki.wikidot.com/
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
Stuttering and the Dysarthrias
Paul Brocklehurst
University of Edinburgh
June 2011
Talk for Scottish dysfluency SIG
Funded by
The Economic and Social Research Council
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
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
West (1929)
“A neurological test for stutterers”
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
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
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)
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?
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
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)
•
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)
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)
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
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.
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)
Dysarthria Types
Type
Locus
(Duffy 2005)
Primary Deficit
Flaccid
Lower motor neurons
Weakness
Spastic
Upper motor neurons
Spasticity
Hypokinetic
Basal ganglia control circuit
Rigidity, distorted
sensory awareness
Hyperkinetic
Basal ganglia control circuit
Involuntary movements
Ataxic
Cerebellar control circuit
Incoordination
Unilateral UMN
Unilateral UMN
Weakness; spasticity
Mixed
More than one
More than one
Dysarthria Types
Type
Locus
(Duffy 2005)
Primary Deficit
Flaccid
Lower motor neurons
Weakness
Spastic
Upper motor neurons
Spasticity
Hypokinetic
Basal ganglia control circuit
Rigidity, distorted
sensory awareness
Hyperkinetic
Basal ganglia control circuit
Involuntary movements
Ataxic
Cerebellar control circuit
Incoordination
Unilateral UMN
Unilateral UMN
Weakness; spasticity
Mixed
More than one
More than one
Hypokinetic Dysarthria – Etiologies (Duffy 2005)
Infectious
Toxic/metabolic 1% Other
1%
2%
Undet.
4%
Traumatic
1%
Multiple
4%
Vascular
9%
e.g. Parkinson’s
Disease
Degenerative
78%
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. armswing 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
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
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.
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)
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.
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.
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.
Hyperkinetic Dysarthrias – Etiologies (Duffy 2005)
e.g. Huntington’s disease
Degenerative
9%
Vascular
1%
Traumatic
1%
Toxic/metabolic
Antipsychotic
12%
drugs
Infectious
1%
Other
6%
Unknown
67%
Large genetic/ hereditary
component
Multiple
3%
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”
– Dyskinesias (e.g. tardive dyskinesia)
jerks)
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
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.
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
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
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)
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
Ataxic Dysarthria – Etiologies (Duffy 2005)
Inflamm.
Toxic/Metabolic 4%
5%
e.g.
Tumor
Alcoholism,
3%
Multiple
1% Other
1%
Valium use
Degenerative
36%
Demyelinating
17%
Mainly
hereditary
e.g.
MS
Undet.
15%
Traumatic
5%
Vascular
13%
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.
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
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.
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.
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’.
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.
Thank you

The Edinburgh Disfluency Group
http://edgwiki.wikidot.com/
References