sl6003 3.1 underlying deficits and diagnosis 2012

Aileen WrightSL6003 3.1 2012

A Model of speech processing and underlying deficits in speech

sound disorders

Obligatory Reading• Differential Diagnosis of phonological

disorders in Dodd (2005)

Learning objectives

Describe the stages and routes used in processing speech in Duggierala & Dodd’s modelDescribe what happens if different parts of the model break downExplain the underlying deficits in each category in Dodd’s classification of speech sound disordersExplain the consequences of the underlying deficits for the child’s speechBe able to differentially diagnose the type of speech sound disorder from an analysis of speech

The McGurk effect

• http://www.youtube.com/watch?NR=1&v=I1XWDOwH47Y

Evidence: how do you account for this?• Children are taken in by the McGurk effect (Dodd & McCormack 2008)• Children can usually recognise spoken word pairs that they are unable

to differentiate in production• Children can imitate nonsense words• Children can sometimes pronounce real words better in imitation than

in spontaneous speech• Children’s speech errors are characterised by consistent errors that can

be elegantly explained by phonological processes/realisation rules, e.g. postconsonantal sonorants delete, e.g. traintein, blue bu, new nu, twintin

• Children sometimes suppress processes in new words, but processes remain in a few very early acquired words

• Children sometimes produce a word correctly, then later start using a less accurate production

Comparison of Stackhouse & Wells and Duggirala & Dodd models

Duggierala & Dodd’s model

Abstract plan. Drives phonetic program that

sets up motor specs

Mental processes that derive artic. Instructions from abstract plan. Includes phonetic specification of phonemes. Assembles the gestural targets (articulatory instructions) into correct sequence in real time, taking into account the context, e.g. assimilations and the appropriate intonation for a question form.

peripheral production of speech at the level of the vocal tract. Gestures required for accurate pronunciation are produced in

form of overt muscular action

Stored plans for high frequency

utterances

Realisation rules:A set of mental processes that govern the construction of a phonological plan

Knowledge about rules of phonological system, eg legal vs illegal consonant combinations

Pragmatic knowledge, rules of social interaction

Analyse incoming data from both modalities to form phonological system

Where the meaning of the word is stored: Mouse small rodent, long tail, eats cheese, lives in hole..

Stored entries of words recording how they sound:Mouse /maʊs/. Contain enough information for a heard word to be recognized as distinct from other similar-sounding words (e.g. TAP vs CAP; CAP vs CAT).

Justification of model (Dodd & McCormack 1995)

Evidence: errors are consistentAcross the board change happens when a process is suppressedPhonological therapy generalises to untreated targets

McGurk effect

Socio-linguistic variation in speech eg “gay speech”

Munson, B. & Babel, M. 2007. Loose Lips and Silver Tongues, or, ProjectingSexual Orientation Through SpeechLanguage and Linguistics Compass 1/5 :416–449,

Processing routes

Input of linguistic knowledge (constraints) to realisation rules

McGurk effect

Repetition of non-words/unknown words

Input from both modalities

Ready made phonological plans for known words

Levels of breakdown on the model (Dodd & McCormack 1995)

Visually impaired children make more errors of place of

artic, rather then manner, unlike non VI

CPD children showed no preference for legal over illegal words: Performed worse on PA tasks than

other gps. lack of knowledge of rules of phon. system?

IC children performed worse in receptive and expressive vocab than Control, PD and

CPD: impaired ability to access full forms of words?

IC gp worse than other 3 on non-verbal motor (tracing) and verbal motor (learning

non words) tasks

IC children made more phonological than phonetic errors: phonological planning deficit rather

than phonetic programmingDelayed gp showed no specific deficit. Just slightly behind controls on all tasks

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YES

• Deficits in auditory processing • Tallal & Piercy 1973, 1974,1975

• Children with SLI/dyslexia have difficulties with fast temporal processing of tones

NO

• Coady, Kuender, Evans 2005• No difficulty if normal speech used rather than

synthetic sound• children distinguish minimal pairs they do not

produce

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3.1 Speech sound disorders

Why Speech disorders? Perceptual deficits

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Why speech disorders?: Cognitive-linguistic impairment:

Lexical deficits?

• Children with inconsistent disorder are poorer in expressive vocab. tests:

• Difficulty word-finding, accessing phonological shape of word?

• Impaired ability to access full specifications of words inconsistent word production

Impaired rule derivation

ability?

• Difficulty abstracting knowledge from mental lexicon about nature of phonological system

• E.g. knowledge of phonological legality: Children with consistent disorder show no preference for legal over illegal nonsense names• Suggests deficit in deducing constraints inherent

in native phonological system• E.g. phonological awareness: Children with

consistent disorder show difficulty with recognising rhyme and alliteration

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Why speech disorders? Output processing

Impaired ability to generate

phonological plans

• Motor accuracy test: tracing • Inconsistent group performed worse

than other gps• Nonsense word learning • Inconsistent group performed worse

than other gps• Suggests inconsistent group have

motor planning problem not specific to speech

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Why speech disorders? Motor execution

Impaired ability to generate phonetic

plans?

• mental processes that derive precise articulatory instructions for the pronunciation of a word from an abstract phonological plan

• Inconsistent gp: more phonological than phonetic errors, therefore no evidence for this

Motor execution

impairment

• Anatomical anomaly, muscle disfunction

• Degree?

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Consistent phonological disorder

Underlying deficit: rule abstraction/pattern recognition

Learning which contrasts are relevant in the ambient language

Determining the statistical patterns in the ambient language so they can efficiently segment continuous speech into word-sized units

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Inconsistent speech disorderHolm, Crosbie & Dodd (2007) Differentiating Normal Variability from Inconsistency in Children's Speech: Normative Data International Journal of Language & Communication Disorders, v42 n4 p467-486

Underlying deficit: phonological planning

i.e. generating a plan that specifies the sequences of consonants and vowels to be produced. • Underspecified or degraded

phonological plans. May be due to:

• having inaccurate phonological representations,

• problems accessing accurate phonological representations

• difficulty setting up the phonological plan.

Incomplete phonological plan leads to inadequate phonetic programmes with articulatory parameters that are too broad. • neural messages that sequence

speech movements provide imprecise instructions.

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Conclusions: underlying deficit

Articulation Disorder

Motor execution

impairment

Delayed:

no specific deficit

Consistent disordered:

cognitive-linguistic deficit:

impaired ability to derive and organise knowledge about nature of ambient phonological system

Inconsistent disordered:

Difficulties with phonological

planning

Degraded phonological

representations, or difficulty

accessing them

Motor planning difficulty

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Conclusions

Skills are inter-related: impairment of one will effect others

Differing impairment profiles indicates areas of general impairment that guide further Ax and intervention

Surface speech error patterns can be described in different ways, but description has limited explanatory power

For profound understanding of speech disorders:

• Different profiles require different patterns of impairment• More generic mental abilities may underlie some kinds of speech disorder

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Diagnosis & the Speech Processing Model

• difficulties in phonetic programming or motor execution

Articulation:

• no apparent specific deficits in speech processing chain. Little behind control on all tasks.

Phonological Delay:

• often have phonological awareness difficulties, indicates a linguistic impairment in deriving knowledge about their language system

Consistent Disordered:

• difficulties with phonological planning

Inconsistent:

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Differential Diagnosis: Articulation disorder

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3.1 Speech Sound Disorder - classification

• Organic ( dysarthria)• Structural anomaly( cleft palate)• Functional articulation disorder

Three types

• Child cannot produce the sound.• Differential diagnosis requires a stimulability probe

Inability to produce a sound in isolation, or in any phonetic context. Same production in spontaneous production as on imitation

• In this case, child may be stimulable for correct sound, but has habituated the wrong sound

OR sound is distorted (not another phoneme) e.g. lateralised /s/, nasal fricative for /s/

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Differential Diagnosis: Phonological delay

• Chronologically mismatched pattern of errors• 6mths+ delay is significant• Changing system or frozen system- monitor for 3mths

or home programme• Child may catch up by themselves• 5 years+: frozen system: not likely to change without

intervention, so needs therapy

The child’s phonological error patterns are those which occur during normal development, but at least some are typical of younger children

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Differential Diagnosis: Consistent Phonological Disorder

• Variety of syllable structures and stress patterns is restricted

• May have developmental patterns also• Only one non- developmental error means disorder• Often have phonological awareness difficulties

Use of non-developmental error patterns (atypical, disordered, unusual, idiosyncratic)

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Differential Diagnosis: Inconsistent Phonological Disorder

• Produce same word in multiple error forms• Not correct/incorrect: maturing system

• Lack of stability in phonological system• Indicates a pervasive speech disorder• Difficulties in phonological planning

At least 40% variability e.g. when asked to name 25 pictures on 3 occasions

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Differential diagnosis: (Dodd et al 2002)

Inconsistent phonological disorder vs.developmental verbal dyspraxia (DVD)• Inconsistent phonological disorder is frequently mis-diagnoses as DVD• Differences:

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Developmental Verbal Dyspraxia Inconsistent Phonological Disorder

Difficulties producing many sounds in isolation

Are able to produce most sounds in isolation

Frequent difficulties with oro-motor skills

Have age appropriate oro-motor skills

Imitation worse than spontaneous production

imitation better than spontaneous productions

More variable productions in different contexts

High degree of inconsistent productions of the same lexical item in the same context- 40%

Characterisation of a SSD• Josh (4:11) presents with an inconsistent phonological disorder and some

developmental processes. Inconsistency is 56% and PCC on the DEAP is 44%. Where he uses them, he is fronting velars and //, and he is gliding /r/ /w/. Other than this his phoneme inventory is age appropriate. He uses 1, 2 and some three syllable words. He produces /l/ blends but no other clusters. Intelligibility is severely reduced for all listeners.

• Mary (3:6) presents with a phonological delay characterised by final consonant deletion of all consonants except nasals and stopping of all fricatives and affricates. She is also using the age-appropriate processes of weak syllable deletion, cluster reduction and gliding of /r//w/. PCC on the DEAP is 62%. Intelligibility is severely reduced for all listeners.

• Paddy (3:11) presents with a consistent phonological disorder characterised by a very limited inventory of consonants (p, b, m ….) and structures (CV, VC, VCV), Word initially all fricatives are produced as /h/. PCC on the DEAP is 57%. Intelligibility is severely reduced for all listeners.

• Aoife (4:11) presents with a mild phonological delay characterised by cluster reduction of all /s/ clusters. She also has an articulation difficulty with //. Otherwise her inventory of phonemes and structures is age appropriate. PCC on the DEAP is 86%. The delay is resulting in reduced intelligibility for unfamiliar listeners.

sl6003 3.1 underlying deficits and diagnosis 2012

Education