adam buchwald new york university buchwald@nyu 18 june 2009
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Distinguishing phonetic processing and motor processing: Evidence from instrumental analysis of acquired speech impairment. DEPARTMENT OF COMMUNICATIVE SCIENCES AND DISORDERS. Adam Buchwald New York University [email protected] 18 June 2009. Spoken language production. - PowerPoint PPT PresentationTRANSCRIPT
Distinguishing phonetic processing and motor processing:
Evidence from instrumental analysis of acquired speech impairment
Adam BuchwaldNew York [email protected]
18 June 2009
DEPARTMENT OF COMMUNICATIVE SCIENCES AND DISORDERS
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Spoken language production
• Producing spoken language requires many levels and processes to be orchestrated– Lexical access in long-term memory; working
memory; articulatory planning and implementation
• Today: relationship between phonetic planning and motor programming– Guided by discussion of:
• Phonetic processing/impairment vs. motor processing/impairment in Apraxia of Speech
• Focus on: Consonant clusters
3
Phonetic plans & motor programs
• “Phonetic plan” ≡ sound structure representation–includes detail re: temporal overlap of gestures, phasing relations–gestural score in articulatory phonology (Browman & Goldstein, 1986,1988, et seq.)
• As in the output of phonetic encoding in some processing accounts (Levelt et al., 1999; Cholin et al., 2004, 2006)
• “Motor programs” ≡ detailed representation encoding temporal overlap of articulators
• Inter-articulator coordination
Are these created by separate systems?
What are the properties of impairment to these systems?
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Consonant clusters
• Syllables with onset clusters contain complex structure and phasing– Onset consonants are coupled to vowels (Browman & Goldstein, 1988;
Byrd, 1996)• Center of consonant timed to onset of vowel• Complicated by presence of a cluster; in English, center of cluster timed to onset of vowel
– Multiple possible ‘repairs’ (or simplifications)• Deletion; changing phasing relation; inserting a vowel
Questions regarding 2 different aphasic/apraxic speaker • How are the consonant clusters repaired?• What properties determine the nature of the repair?
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VBRBuchwald, Rapp & Stone, 2007
• 57, RH, F
• Suffered CVA at 51– large LH fronto-parietal
infarct involving posterior frontal lobe, including Broca's area, pre- and post-central gyri and the SMG
• Dysfluent spoken production, mainly single-word utterances
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VBR and schwa insertion
• Difficulty producing complex onsets– Produces consonant clusters with a vowel inserted
between the two consonants– e.g., bleed [bəlid]
• Robust pattern– Occurs with different modalities of presentation
(naming, repetition, reading)
• What is the nature of these errors?– Epenthesis vs. Articulatory (mis)timing
believe
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Epenthesis vs. Mistiming
Epenthesis
C1 C2
• Vowel inserted in gestural score
Gestural mistiming
C1 C2
• Consonant gestures mistimed–Audible release of C1
Open vocal tract
Target:
C1 C2
əə
onset
target release
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Ultrasound study
• Examine articulations to see whether inserted schwa is like lexical schwa
• Produce word pairs: bleed-believe– Matched on C1, C2, and stressed V
• Compare tongue contours – If epenthesis: inserted schwa = lexical schwa
– If mistiming: inserted schwa ≠ lexical schwa
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Inserted schwa = Lexical schwa
Back Tongue Position Front
Red – Inserted
Blue – Lexical
Within-category differences
EQUAL
across-category differences
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Consonant cluster repair: schwa epenthesis
• The inserted vowel is the result of epenthesis– Articulatory data from ultrasound: tongue contour of
inserted vowel similar to lexical vowel• Similar variability between vowels and within vowel types• Supported by acoustic data (duration, variability, co-
articulation)
• Systematic epenthesis repair of obstruent-sonorant clusters– Removes structural (and articulatory) complexity by
adding schwa to phonetic plan
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DLEBuchwald, Rapp & Miozzo, 2009
• 72 year old aphasic/apraxic speaker• Spoken production limited – short phrases; labored • Produces systematic consonant cluster errors in
deletion of /s/ from /s/-stop and /s/-nasal clusters
• Question: at what level does deletion take place? – Is deletion part of phonetic plan or does it occur during
generation of motor program?
smash mashsteer tier deer
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Phonetic errors vs. motor errors
• Phonetic planning precedes motor programming• If phonetic plan has no /s/, then the token has singleton onset
consonant and should be produced accordingly• If phonetic plan has /s/ and deletion occurs at motor level, then
timing should be appropriate for cluster– Compare tokens with deleted /s/ to singletons– Use acoustic properties of language to help with this
• /s/-stops: VOT in spin is closer to bin than pin• /s/-nasals: nasal duration in snail shorter than nasal in nail
– Paired comparisons of target clusters with singletons• e.g., speak vs. peak, beak• e.g., smash vs. mash
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Hypotheses
• Phonetic planning errors– Stops in deletions more similar to singleton voiceless stops
• Reflects /s/ being absent from phonetic plan
– Nasals in deletions same duration as singleton nasals• Reflects /s/ being absent from phonetic plan
• Motor programming errors– Stops in deletions more similar to singleton voiced stops
• Reflects /s/ being absent from phonetic plan
– Nasals in deletions shorter than singleton nasals• Reflects /s/ being absent from phonetic plan
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/s/-stop and singleton stop VOT
• What factors increase the likelihood of repair?
Labial Alveolar Velar
(s)-stop 27.5 44.4 68.5
voiceless 30.5 43.9 77.8
voiced 21.9 33.8 44.3
N 79 103 25
Labial Alveolar
Velar
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/s/-nasal duration
020406080
100120140
sN N
dura
tion
(in m
s)
• Nasal duration and VOT both reflect the production of a phonetic plan generated without an /s/
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Phonetic planning errors
• These two cases of apraxia both exhibit phonetic planning errors– Does not mean these are the only possible errors; just
happens to be the case here
• What to do with these errors?– Examine factors that influence the incidence and
nature of these errors to learn about phonetic planning system
– For each individual, we see effects of (relatively abstract) phonological representations on their errors
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Phonological effects: VBR
• VBR: epenthesis errors in obstruent-sonorant clusters– Words with C/j/ onset (e.g., cute) argued to have complex
vocalic diphthong (/ju/) rather than cluster
• If #Cw sequences (as in queen, quote) are clusters:– Should be repaired via epenthesis
• If #Cj as in cute, music are clusters:– Should be repaired via epenthesis, as other clusters
– Never repaired via epenthesis– Repaired via deletion: /kjut/ [kut]
cute music
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Phonological effects: DLE
• DLE: /s/-deletion in obstruent-obstruent and obstruent-nasal clusters– English has a few other obstruent-obstruent and
obstruent-nasal onsets (/∫/-initial)
• If DLE’s ‘repair’ can be expressed over natural classes, should similarly affect these sequences
– In addition, other sonority-based descriptions affect error rate – deletion very rare in /sl/ and /∫r/ clusters
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Summary and future directions
• Instrumental analyses of apraxic/aphasic speech can show errors of phonetic planning– Phonetic planning errors appear to be affected by phonological
properties, leading to systematic sound structure repairs
• Future work– Explore error systematicity as a way to determine whether errors
– Extend analyses to other impairments, particularly motor programming impairment and children with speech sound impairments (with HBK, CR)
– Incorporate other speech production instruments (EMMA? Real-time MRI?)
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Acknowledgements
Brenda Rapp
Maureen Stone
Michele Miozzo
Paul Smolensky
VBR
DLECettina Chiarelli
Cristina Sanchez