speech motor deficits in cerebral palsied children an acoustic perceptual approach n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Speech Motor Deficits in Cerebral Palsied Children: An Acoustic-Perceptual Approach PowerPoint Presentation
Download Presentation
Speech Motor Deficits in Cerebral Palsied Children: An Acoustic-Perceptual Approach

Loading in 2 Seconds...

play fullscreen
1 / 44

Speech Motor Deficits in Cerebral Palsied Children: An Acoustic-Perceptual Approach - PowerPoint PPT Presentation


  • 491 Views
  • Uploaded on

Speech Motor Deficits in Cerebral Palsied Children: An Acoustic-Perceptual Approach. 1 Department of Communication Disorders, University of Canterbury, Christchurch, New Zealand 2 Department of Physical Medicine and Rehabilitation, Chang Gung Memorial and Children Hospital, Taoyuan, Taiwan

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Speech Motor Deficits in Cerebral Palsied Children: An Acoustic-Perceptual Approach' - omer


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
speech motor deficits in cerebral palsied children an acoustic perceptual approach

Speech Motor Deficits in Cerebral Palsied Children: An Acoustic-Perceptual Approach

1Department of Communication Disorders, University of Canterbury, Christchurch, New Zealand

2Department of Physical Medicine and Rehabilitation, Chang Gung Memorial and Children Hospital, Taoyuan, Taiwan

3Department of Physical Therapy, Chang Gung University, Taoyuan, Taiwan

The 5th Asia Pacific Conference on Speech, Language and Hearing

Brisbane, Australia

July 9-13, 2007

Emily Lin, PhD1, Chia-Ling Chen, MD, PhD2, 3, & Chao-Chin Lee, BSLT1

research question
Research Question
  • What are the acoustic measures useful for detecting incorrect speech productions in children with cerebral palsy?
why acoustic measures
Why Acoustic Measures?
  • Acoustic recording is non-invasive.
  • Acoustic signal is
    • Objective/instrumental
    • A link between speech production and perception, allowing for assessment of:
      • Placement/movement of articulators (e.g., tongue) or vocal tract configuration
      • Speech intelligibility
purpose of the study
Purpose of the Study
  • To identify acoustic measures sensitive to changes of speech motor control in cerebral palsied children related to the perception of speech production errors
cerebral palsy cp
Cerebral Palsy (CP)

Definition (Blaire & Watson, 2006):

  • a disorder of movement or posture
  • related to static (non-progressive) abnormality in the brain
  • acquired early in life (before or after birth; when the brain is still immature and developing)

Prevalence:

  • 1 (Cerebral Palsy Society of New Zealand, 2000) or 2 (Platt & Pharoah, 1995; Blair, 2001; Hagberg, Hagberg, Beckung & Uvebrant, 2001)per 1000 live births.
motor signs of cp
Motor Signs of CP
  • Rigidity
  • Flaccidity
  • Spasticity (increased rigidity in a group of muscles)
  • Ataxia (poor coordination)
  • Dyskinesia (jerky motion)
  • Athetosis (weak but controllable movement)
  • Tremor
  • Chorea (involuntary uncontrollable movements of body and face along with marked incoordination of limbs)
aetiology of cp
Aetiology of CP

(Little, 1862)

Birth Asphyxia

Birth Asphyxia

(Denhoff, 1976; Blair & Stanley, 1997; Hagberg et al., 2001)

Intrauterine viral infections e.g. Rubella & Cytomegalo-virus (CMV)

Intrauterine viral infections e.g. Rubella & Cytomegalovirus (CMV)

Low gestation age

(Denhoff, 1976;

Hagberg & Mallard, 2000;

Blair & Stanley, 1993; Stanley, 1997)

Maternal thyroid abnormalities

Low Apgar scores

(Nelson & Ellenberg, 1981)

Cerebral

Palsy

(Risk Factors)

(Blair & Stanley, 1993; Stanley, 1997)

Perinatal exposure: Methyl mercury

Multiple gestation

(Amin-Zaki, Majeed, Elhassani et al., 1979; Stanley, 1997)

(Nelson & Grether, 1999)

Iodine deficiency

Male gender:

1.9:1 to 0.99:1 (M:F)

(Blair & Stanley, 1997)

(Pharoah, Buttfield & Hetzel, 1971)

speech characteristics of cp
Speech Characteristics of CP

↓ Speech Intelligibility

↓ Speech Naturalness

(Kent, Netsell, & Abbs, 1978)

  • Prosody
  • Slow rate
  • Arythmatic

(Hixon & Hardy, 1964)

(Andrews, 1999)

(Hardy, 1961; Kent & Netsell, 1978)

speech pattern in cp
Speech Pattern in CP
  • Dysarthria* is often found in CP speech
    • Frequency of dysarthria in CP: 31%-88%

* Dysarthria is characterized by centralized vowel articulation as well as reduced articulatory precision for fricatives and affricates (Ansel and Kent, 1992)

  • Highly variable: Pattern and severity depends on the underlying pathophysiology
    • Spastic CP: low pitch, hypernasality, pitch breaks, breathy voice, excess & equal stress (Workinger & Kent, 1991)
    • Athetoid CP:irregular articulatory breakdowns, inappropriate silences, prolonged intervals and speech sounds, excessive loudness variation, voice breaks

(Yorkston, Beukelman, Strand, & Bell, 1999)

slide11
Formants 1 (F1) & 2 (F2):

Critical to vowel perception (Peterson & Barney, 1952)

F1 relates to tongue height & F2 to tongue advancement (Kent et al., 1999)

Related to overall speech intelligibility (Turner, Tjaden & Weismer, 1995; Ansel & Kent, 1992; Liu, Tsao & Kuhl, 2005; Liu, Tseng & Tsao, 2000; Whitehill & Ciocca, 20)

Vowel Space (F1-F2 Plot)

vowel working space speech intelligibility
Vowel Working Space & Speech Intelligibility

Cerebral Palsy (CP)

Multiple Sclerosis (MS)

Amyotrophic Lateral

Sclerosis (ALS)

Normal Speakers

Parkinson’s Disease (PD)

  • Tjaden & Wilding (2004)
    • MS (N=15), PD (N=12) & controls (N=15)
    • Corner vowels: /i/, /a/, /ӕ/ & /u/ in habitual, loud & slow (passage)
    • Perceptualanalysis & Acoustic analysis
    • Size of vowel working space area & speech intelligibility seems to be unrelated in MS group
    • Tjaden & Wilding (2005)
    • Weismer, Martin, Kent & Kent (1992)
  • Turner, Tjaden & Weismer (1995)
  • Weismer, Laures, Jeng, Kent & Kent (2000)
  • ALS (N=10) & controls (N=19)
  • Corner vowels: /ӕ/, /a/ & /u/ in habitual & fast speaking rate
  • Perceptual analysis & Acousticanalysis
  • Increased rate resulted in reduced vowel working space, but no change in speech intelligibility
  • Weismer, Jeng, Laures, Kent & Kent (2001)
  • Tjaden, Rivera, Wilding & Turner (2005)
  • Weismer et al. (2001)
  • PD (N=10), ALS (N=10) & controls (N=19);
  • Corner vowels: /i/, /ӕ/, /a/ & /u/ in habitual rate & intensity;
  • Perceptual analysis & Acoustic analysis;
  • Vowel working space reduced (no significance for PD); correlated with speech intelligibility (reduced in both groups)
  • Tjaden & Wilding (2004)
  • Tjaden et al.(2005)
  • Liu et al. (2005)
    • Mandarin speakers with CP (N=20) & controls (N=10);
    • Corner vowels: /i/, /a/ & /u/ in habitual speaking rate;
    • Perceptualanalysis & Acoustic analysis;
    • Significant correlation between vowel working space & speech intelligibility
  • Fourakis (1991)
  • Healthy individuals (N=8 )
  • 9 vowels in different rate & stress
  • Vowel working space was largest during slow stressed speech
  • Bradlow, Toretta & Pisoni (1996)
    • Healthy individuals (N= 20)
    • Vowels: /i/, /a/ & /oʊ/ in habitual speaking rate
    • Perceptualanalysis & Acousticanalysis
    • Increased vowel space area were positively correlated with increased intelligibility
summary of literature review
Summary of Literature Review
  • Spastic type is most prevalent in CP.
  • Dysarthria is a common feature in CP speech.
  • Involuntary abnormal prosodic pattern can be an indication of speech motor deficits.
  • Acoustic-perceptual studies revealed a positive relationship between vowel space and speech intelligibility in CP, suggesting that vowel space may be a useful acoustic measure for detecting speech motor difficulties.
hypothesis
Hypothesis
  • Acoustic difference between incorrectly and correctly produced speech sounds can be used to detect subtle articulatory changes and reflect loss of phonemic contrast (and thus compromised speech intelligibility).
research design
Research Design
  • Subjects as own controls
  • Compare error rates in producing different phonemic contrasts
  • Describe the temporal and spectral characteristics of the acoustics of the incorrectly produced vowels and consonants
method
Method
  • Convenience sampling:
    • Cerebral Palsied Children referred to the Department of Pediatric Rehabilitation at Chang-Gung Memorial Hospital (Tao-Yuan, Taiwan) in 2005
  • Subject Selection:
    • Inclusion criteria:
      • Cerebral palsied children
      • Native speakers of Mandarin
    • Exclusion criteria:
      • Mental retardation
      • Hearing impairment
      • Cognitive and sensory impairment
      • Epilepsy
subjects
Subjects
  • Age: 7 – 15 years
  • 1 female (spastic quadriplegia*) and

5 males (2 spastic quadriplegia & 3 spastic diplegia*)

*Quadriplegia: four limb involvement with unsymmetrical

severity on two sides;

Diplegia: four limb involvement with symmetrical severity on

both sides and with the lower limb involvement usually more severe than the upper limb

subject s task
Subject’s Task
  • Read a list of 140 Mandarin 2-word phrases [CV(N)-CV(N)]* containing minimal pairs contrasting consonants (21), vowels (16), and tones (4)
    • Each of the 140 items was read twice in a sequence
    • Words were presented in the form of orthography with phonemic transcription on the side.
    • Examples:

“ratio”: /pi3 li4/ “grain of rice”: /mi3 li4/

* C = consonant; V = vowel; N = nasal

recording procedure
Recording Procedure
  • Subject seated in a quiet room and asked to perform subject’s task, with the recording device in place.
    • Microphone placed 15 cm from the lips
    • Direct digitization (Sampling rate: 44KHz)
    • No modeling was provided
listeners and listener s task
Listeners and Listener’s Task
  • Two native Mandarin speakers trained in the field of speech pathology
  • Error Identification Task:
    • Listen to acoustic signals played back through a computer sound card and speakers
      • One 2-word phrase at a time
      • Repeated listening allowed
    • Circle, on the word list, vowels, consonants, and tones perceived to be incorrectly produced
    • Perform the task individually, being blind to the CP type
    • Repeat the whole session a second time (for reliability analysis)
acoustic measurement
Acoustic Measurement
  • Temporal measures:
    • Syllable length
    • Consonant length
    • Vowel length
  • Formant analysis of vowels (Baken, 1987) :
    • Formant 1 frequency (F1)
    • Formant 2 frequency (F2)
  • FFT spectral moment analysis of consonants (Forrest, Weismer, Milenkovic, & Dougall, 1988):
    • Moment 1 (M1): mean
    • Moment 2 (M2): standard deviation
analysis software
Analysis Software
  • TF32(copyright: 2000 Paul Milenkovic)
    • Time lengths of individual vowels & consonants
    • F1 & F2 frequencies: LPC (Linear Predictive Coding) algorithm
  • PRATT(copyright: 2005 Paul Boersma & David Weenink)
    • Moment analysis
reliability
Reliability
  • Perceptual identification of production errors:
    • Intra-judge total reliability:
      • Consonant: 88.4%, 92.4%
      • Tone: 86.7%, 84.9%
      • Vowel: 81.5%, 84.7%
    • Inter-judge total reliability:
      • Consonant: 85.4%
      • Vowel: 80.6%
      • Tone: 65.6%
  • Acoustic measurement:

Measure-remeasure reliability (20% data):

      • Consonant length: 97.9
      • Syllable length: 94.9%
      • Vowel length: 93.7%
      • Speech Moment 1: 95.4%
      • Speech Moment 2: 93.1%
      • F1: 82.6%
      • F2: 73.3%
results

100

Sub1

Sub2

80

Sub3

Sub4

Percent

Sub5

60

correct

Sub6

(in %)

40

20

0

Consonant

Vowel

Tone

Type of Phoneme

Results
  • Consonants exhibited the lowest rate of correct productions.
distribution of consonant errors
Distribution of Consonant Errors
  • Frequency of correct production lower than 40%:
    • / /, / /, / /, / / (retroflex): Subjects 1 to 4
    • /ts’/ (aspirated affricate): Subjects 2 and 6
speech moments 1 2
Speech Moments 1 & 2
  • Incorrect consonants cluster more together in the M1-M2 plot than their correct counterparts.
    • M1 & M2 were lower for incorrect consonant production involving frication or affrication.
    • M1 & M2: When produced correctly, retroflexed tend to have lower M1 & M2 than their

non-retroflexed counterparts. But incorrect productions were inconsistent.

    • M1: When produced correctly, un-aspirated plosives were lowered than their aspirated

counterparts. But incorrect productions were inconsistent.

vowel space
Vowel Space
  • Vowels following incorrectly produced consonants exhibited a more
  • compressed vowel space than those following correctly produced consonants.
consonant length
Consonant Length
  • Incorrectly produced consonants (n = 98) were significantly longer than
  • correctly produced ones (n = 618) in both first-word/syllable (T =43284.5,
  • p < 0.001) and second-word/syllable positions (T = 65669, p < 0.001).
vowel length
Vowel Length
  • Incorrectly produced consonants (n = 98) were found to be associated with
  • vowels significantly shorter than vowels in correctly produced consonants
  • (n = 618) only in the first-word/syllable position (T = 29378, p = 0.003) but
  • not in the second-word/syllable position (T = 56302, p = 0.567).
summary
Summary
  • Error Patterns:
    • No difference between diplegia & quadriplegia
    • Mostly consonant errors (esp. frication, affrication, retroflex)
  • Acoustic characteristics of incorrect production:
    • Consonant:
      • Consonant length prolonged
      • Retroflexed consonants:

- M1 contrast inconsistent

      • Fricatives and affricates:
        • Lower M1: suggesting a more posterior tongue placement
        • Lower M2: suggesting less diffusion of frication noise
summary continued
Summary - continued
  • Vowels following incorrect consonants:
    • Vowel length shortened
    • Vowel space compressed, suggesting
      • Production: more restrained vocal tract shaping
      • Perception: less speech intelligibility
clinical implications
Clinical Implications
  • Temporal and spectral measures are useful for detecting subtle changes in speech motor control.
  • The found impact of an incorrect consonant on the vowel immediately following it suggests that vowel manipulation (e.g., change in length or extent of jaw opening) may help compensating for the loss of vowel clarity as well as overall speech intelligibility (i.e., reversing the adverse effect with anticipatory coarticulation).
follow up
Follow-up
  • Increased sample size
  • Effect of facilitation strategies (rate, overarticulation)
  • Listening task effect: blinded phonemic (especially tone) transcription task vs. error identification task with known phonemic representations
  • Effect of spectral analysis software
conclusion
Conclusion
  • Spastic CP exhibits mostly consonant errors, which are associated with a compressed vowel space.
  • Tone errors may be a secondary problem for CP children but this requires further studies examining the effect of listening task.
  • A selection of temporal and spectral measures are useful for differentiating correct and incorrect productions by CP children.
acknowledgement
Acknowledgement
  • Fiona Yip, BSLT, Department of Communication Disorders, University of Canterbury
slide36

References

Ackermann, H., Hetrich, I., & Hehr, T. (1995). Oral diadochokinesis in neurological dysarthrias. Folia phoniatrica et logopaedica, 47, 15-23.

Amin-Zaki, L., Majeed, M. A., Elhassani, S. B., Clarkson, T. W., Greenwood, M. R. & Doherty, R. A. (1979). Prenatal methylmercury poisoning: clinical observations over five years. American Journal of Disease in Childhood, 133(2), 172-177.

Ansel, B. M., & Kent, R. D. (1992). Acoustic-Phonetic Contrasts and Intelligibility in the Dysarthria Associated with Mixed Cerebral Palsy. Journal of Speech and Hearing Research, 35, 296-308.

Baken, R. J. (1987). Clinical Measurement of Speech and Voice. Austin, Texas: Pro-ed.

Bax, M. (1964). Terminology and classification of cerebral palsy. Dev. Med. Child Neurol, 6, 295-297.

Bradlow, A. R., Toretta, G. M., & Pisoni, D. B. (1996). Intelligibility of normal speech I: Global and fine-grained acoustic-phonetic talker characteristics. Speech Communication, 20, 255-272.

slide37

Bellaire, K., Yorkston, K. M., & Beukelman, D. (1986). Modification of breath patterning to increase naturalness of a mildly dysarhtria speaker. Journal of Communication Disorders, 19, 271-280.

Blair, E. (2001). Trends in cerebral palsy. Indian Journal of Pediatrics, 69(5), 433-438.

Blair, E. & Stanley, F. (1997). Issues in the classification and epidemiology of cerebral palsy. Mental Retardation and Developmental Disabilities Research Reviews, 8 (3), 184-193.

Blair, W. & Watson, L. (2006). Epidemiology of cerebral palsy. Seminars in Fetal & Neonatal Medicine, 11, 117-125.

Cerebral Palsy Society of New Zealand (2007). Cerebral Palsy. Retrieved April, 3, 2007, from http://www.cpsoc.org.nz/CP/index.htm#prelev

Chao, Y. R. (1948). Mandarin primer. Cambridge Harvard University Press.

Collins, S., Markova, I., & Murphy, J. (1997). Bringing conversations to a close: the management of closings in interactions between AAC users and 'natural' speakers . Clinical Linguistics & Phonetics, 11(6), 467-493.

Colver, A. F. & Sethumadhavan, T. (2003). The term diplegia should be abandoned. Arch. Dis. Child, 88, 286-290.

slide38

Denhoff, E. (1976). Medical Aspects. In W. M. Cruickshank (Ed.), Cerebral palsy: A developmental disability (3rd ed., pp. 29 - 71). New York: Syracuse University Press.

Dromey, C. (2000). Articulatory kinematics in patients with parkinson disease using different speech treatment approaches. Journal of Medical Speech-Language Pathology, 8(3), 155-161.

Finley, W. W., Niman, C. A., Standley, J., and Wansley, R. A. (1977). Electrophysiolgoica behaviour modification of frontal EMG in cerebral-palsied children. Biofeedback and Self-Regulation, 2, 59-79.

Fourakis, M. (1991). Tempos, stress, and vowel reduction in American English. The Journal of Acoustical Society of America, 90(4), 1817-1827.

Hagberg, B., Hagberg, G., Beckung, E. & Uvebrant P. (2001). Changing panorama of cerebral palsy in Sweden. VIII. Prevalence and origin in the birth year 1991-94. Acta Paediatrica, 90(3), 271-277

Hagberg, H. & Mallard, C. (2000). Antenantal brain injury: aetiology and possibilities of prevention. Seminars in Neonatology, 5(1), 41-51

Hardy, J. C. (1983). Cerebral Palsy. New Jersey: Prentice-Hall, Inc.

slide39
Hunter, L., Pring, T., & Martin, S. (1991). The use of strategies to increase speech-intelligibility in cerebral-palsy - an experimental evaluation. British Journal of Disorders of Communication, 26, 163-174.
  • Jeng, J.-Y. (2000). Intelligibility and acoustic characteristics of the dysarthria in mandarin speakers with cerebral palsy. University of Wisconsin-Madison dissertation.
  • Jeng, J.-Y., Weismer, G., and Kent, R. D. (2006). Production and perception of Mandarin tone in adults with cerebral palsy. Clinical Linguistics and Phonetics, 20, 67-87.
  • Kent, R. D. (1993). Vocal tract acoustics. Journal of Voice, 7 (20), 97-117.
  • Kent, R. D., Weismer, G., Kent, J. F., Vorperian, H. K., & Duffy, J. R. (1999). Acoustic studies of dysarthric speech: Methods, progress, and potential. Journal of Comminication Disorders, 32, 141-186.
  • Kleinow, J., Smith, A., Ramig, O. L. (2001). Speech motor stability in IPD: Effects of rate and loudness manipulations. Journal of Speech, Language, and Hearing Research, 44(5), 1041-1051.
  • Levitt, S. (1995). Treatment of Cerebral Palsy and Motor Delay, (2nd ed.). Oxford: Blackwell.
slide40
Li, C. N. & Thompson, S. A. (1977). The acquisition of tone in Mandarin-speaking children. Journal of Child Language, 4, 185-200.
  • Little, W. J. (1969). On the influence of abnormal parturition, difficult labour, premature birth and asphyxia neonatorum on the mental and physical conditions of the child, especially in relation to deformities. Archives of Neurology, 20(2), 218-&.
  • Liu, H.-M., Tsao F-M., and Kuhl P. K. (2005). The effect of reduced vowel working space on speech intelligibility in Mandarin-speaking young adults with cerebral palsy. Journal of the Acoustical Society of America, 117, 3879-3889.
  • Liu, H.-M., Tseng, C.-H., and Tsao, F.-M. (2000). Perceptual and acoustic analysis of speech intelligibility in Mandarin-speaking young adults with cerebral palsy. Clinical Linguistics and Phonetics, 14, 447-464.
  • Milstein, C. F. & Watson, P. J. (2004). The effect of lung volume initiation on speech : a perceptual study. Journal of Voice, 18(1), 38-45.
  • Monsen, R.B. (1976). Normal and reduced phonological space: The production of English vowels by deaf adolescents. Journal of Phonetics, 4, 189-198.
  • Moore, C. A., & Scudder, R. R. (1989). Coordination of jaw muscle activity in parkinsonian movement: Description and response to traditional treatment. In K. M. Yorkstonm, & D. R. Beukelman (Eds). Recent advances in clinical dysarthria (pp. 147-164). Austin, TX: ProEd.
slide41
Nelson, K. B., & Ellenberg, J. H. (1981). Apgar Scores as Predictors of Chronic Neurologic Disability. Pediatrics, 68(1), 36-44.
  • Nelson, K. B. & Grether, J. K. (1999). Causes of cerebral palsy. Current opinion in pediatrics, 11(6), 487-491.
  • Pennington, L., Goldbart, J., & Marshall, J. (2004). Interaction training for conversational partners of children with cerebral palsy: a systematic review. International Journal of Language and Communication Disorders, 39 (2), 151-170.
  • Peterson, G., & Barney, H. (1952). Control methods used in a study of the vowels. The Journal of the Acoustical Society of America, 32, 693-703.
  • Pharoah, P. O., Buttfield, I. H. & Hetzel, B. S. (1971). Neurological damage to the fetus resulting from severe iodine deficiency during pregnancy. Lancet, 1(7694), 308-310.
  • Platt, M. J. & Pharoah, P. O. D. (1995). Epidemiology of cerebral palsy. Current Paediatircs, 5, 151-155.
  • Portnoy, R. A., and Aronson, A. E. (1982). Diadochokinetic syllable rate and regularity in normal and in spastic and ataxic dysarthric subjects. Journal of Speech and Hearing Research, 47, 324-328.
  • Rackensperger, T., Krezman, C., Mcnaughton, D., Williams, M. B., & D’Silva, K. (2005). “When I first got it, I wanted to throw it off a cliff”: The challenges and benefits of learning AAC technologies as described by adults who use AAC. Augmentative and Alternative Communication, 21(3), 165-186.
slide42

Rutherford, B. R. (1944). A comparative study of loudness, pitch, rate, rhythm, and quality in speech of children handicapped by cerebral palsy. The Journal of Speech Disorders, 9(3), 263-271 .

Rutherford, B. R. (1950). Give Them a Chance to Talk: Handbook on Speech Correction for Cerebral Palsy. Minneapolis, Minnesota: Burgess Publishing Co.

Stanley, F. J. (1997). Prenatal determinants of motor disorders. Acta Paediatrica, 422, 92-102.

Tjaden, K., & Liss, J. M. (1995). The role of listener familiarity in the perception of dysarthric speech. Clinical Linguistics & Phonetics, 9(2), 139-154.

Tjaden, K., Rivera, D., Wilding, G., & Turner, G. S. (2005). Characteristics of the lax vowel space in dysarthria. Journal of Speech Language and Hearing Research, 48(3), 554-566.

Tjaden, K., & Wilding, G. E. (2004). Rate and loudness manipulations in dysarthria: acoustic and perceptual findings. Journal of Speech, Language and Hearing Research, 47(4), 766-783.

Tse, J. K.-P. (1978). Tone acquisition in Cantonese: a longitudinal case study. Journal of Child Language, 5, 191-204.

slide43
Turner, G. S., Tjaden, K., & Weismer, G. (1995). The influence of speaking rate on vowel space and speech intelligibility for individuals with amyotrophic lateral sclerosis. Journal of Speech and Hearing Research, 38, 1001-1013.
  • Watson, P. J., Ciccia, A. H., & Weismer, G. (2003). The relation of lung volume initiation to selected acoustic properties of speech. The Journal of teh Acoustical Society of America, 113(5), 2812-2819.
  • Weismer, G., Laures, J. S., Jeng, J., Kent, R. D., & Kent, J. F. (2000). Effect of speaking rate manipulations on acoustic and perceptual aspects of the dysarthria in amyotrophic lateral sclerosis. Folia Phoniatrica et Logopaedica, 52(5), 201-219.
  • Weismer, G., Martin, R. Kent, R. D. & Kent, J. F. (1992). Formant trajectory characteristics of males with amyotrophic lateral sclerosis. The Journal of the Acoustical Society of America, 91(2), 1085-1098.
  • Whitehill, T. L., & Ciocca, V. (2000). Speech errors in Cantonese speaking adults with cerebral palsy. Clinical Linguistics & Phonetics, 14( 2), 111-130.
  • Wohlert, A. B., & Hammen, V. L. (2000). Lip muscle activity related to speech rate and loudness. Journal of Speech, Language, and Hearing Research, 43, 1229-1239.
  • Wolfe, W. G. (1950). A comprehensive evaluation of fifty cases of cerebral palsy. Journal of Speech and Hearing Disorders, 15, 234-251.
slide44

Yorkston, K. M., & Beukelman, D. (1981). Ataxic dysarthria: Treatment sequences based on intelligibility and prosodic considerations. Journal of Speech and Hearing Disorders, 46, 398-404.

Yorkston, K. M., Beukelman, D. R., Strand, E. A., & Bell, K. R. (1999). Management of Motor Speech Disorders in Children and Adults. Austin, TX: Pro-ed.

Yorkston, K. M., Hammen, V. L., Beukelman, D. R., & Traynor, C. D. (1990). The effect of rate control on the intelligibilityy and naturalness of dysarthria speech. Journal of Speech and Hearing Disorders, 55, 550-561.