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Unlocking the Nature of the Phonological–Deep Dyslexia Continuum:
The Keys to Reading Aloud Are in Phonology and Semantics
Jenni Crisp and Matthew A. Lambon Ralph
Reading Models The Dual Route Model The Triangle Model of Reading (Coltheart) (Seidenberg and McClelland)
Dyslexia
Acquired Developmental
Acquired Dyslexia
Peripheral Central ► Neglect ► Deep ► Letter by Letter ► Phonological ► Attentional ► Surface ► Visual
Surface Dyslexia
• Impairment in the visual
input lexicon
• Reading through grapheme-
phoneme conversion
• More accuracy in reading
orthographically regular words
than irregular (e.g. listen)
• Errors reflect typical pronunciation ( e.g. PINT mint)
The Primary Systems Hypothesis (Patterson & Lammbon Ralph, 1999)
Surface Dyslexia:
Semantic impairment
produces impairment
in a predictable range
of language and non-
language activities
What about phonological
and deep dyslexia?
Phonological Dyslexia
►Central Feature – Lexicality Effect
Impairment in grapheme-phoneme
► No problem in semantics
• Cannot read pseudowords /
can read familiar words
• Some visual (badge – bandage)
and derivational errors (edition/or)
• Some effect of part of speech
(functors < verb < adj < nouns)
• Some effect of imageability (abstract<concrete)
Deep Dyslexia
► Impairment in grapheme-
phoneme conversion
► Central feature - Semantic errors
• Semantic paralexias (sergeant /soldier)
• Visual (badge – bandage) and
derivational errors (edition – editor)
• Abolished or very poor reading of
pseudo words
• Effect of part of speech (functors<verb <adj <nouns)
• Effect of imageability (abstract<concrete)
Acquired Dyslexia Surface Phonological Deep dyslexia dyslexia dyslexia
A continuum?
► Do phonological dyslexia and deep dyslexia simply reflect different degrees of impairment?
► What is their possible overlap?
► Is there a continuum in which deep dyslexia is the end point?
phonological dyslexia deep dyslexia
The Continuum Hypothesis
Friedman (1996) A review:
• 5 patients evolved from deep to phonological dyslexia during course of recovery
• Semantic parlexias were first symptoms to change
• Nonword reading was last symptom to change BUT no complete recovery occurred
More Evidence For Continuum Hypothesis
Friedman (1996)
A review of 11 published case reports showed:
• a consistent progression of symptoms
• an order in which reading symptoms emerged
Friedman’s Severity-based Succession
Patient Poor Nonword Visual Nouns> Noun> Concrete> Semantic Reading Errors Functors Verbs Abstract Errors
Expected Pattern Severe Mild Unexpected Patterns
Two coexisting impairments?
Two deficits (Friedman 1996):
• disruption of the orthographic
phonological connections
→ phonological dyslexia
• a semantic impairment accounts
for the remaining dyslexia symptoms
Assessing the notion of phonological-deep dyslexia
• Current literature was dominated by single case studies.
• This study used a case series of phonological-deep dyslexics (the largest to date).
Research Questions
1. How strong is the link or overlap between phonological and deep dyslexia?
2. Is phonological - deep dyslexia accompanied by phonological / semantic deficits?
3. Can it be demonstrated that the degree of these impairments predicts the patients’ dyslexia symptoms?
4. Can the symptoms associated with their reading deficits be elicited in nonreading tasks as the Primary Systems Hypothesis would predict?
Participants
12 dyslexics (10 M, 2 F)
(10 aged matched controls)
Participants
From 40 to 83 years (Mean
age 59.4, SD 11.4))
Age
Between 6 and 156 (Mean 53
months, SD 47.2)
Months post onset (cere-
brovascular accident)
Limited – Left hemisphere
infraction confirmed in 8 cases
Structural scanning
Assessments
The first 12 participants demonstrating at least one of the following in reading aloud were chosen for this study:
• a lexicality effect
• an imageability effect
• production of semantic paralexias
For each participant:
• 29 assessments
• 6-10 testing sessions
• One hour a session
Assessments in exploring the phonological–deep continuum
Reading aloud:
• matched lists of high and low imageability/ frequency words
• matched lists of words with varying syllable length
• matched lists of regular and irregular words
• words of different grammatical classes
• inflected/ affixed words
• nonwords
Assessing Semantic and Phonological Impairment
Assessing semantics:
• Synonyms judgment tests
• Word picture matching
• Semantic association
• Picture naming
Assessing phonology:
• phonological manipulation tasks
• rhyme judgment
• rhyme production
• word and nonword repetition
• delayed word and nonword repetition
Basic orthographic and phonological recognition:
• upper and lowercase letter matching tasks
• visual recognition of degraded letters
• auditory discrimination of nonword minimal pairs
Results & Discussion
1. How strong is the link or overlap between phonological and deep dyslexia?
Max LR MM RJ RS AB NS MR BN TJ PG TH DB Controls Score (Normal cutoff)
Age(years) 58 58 40 64 83 51 72 52 60 66 48 61
Months postonset 156 120 18 31 14 96 28 42 68 28 31 6
1. Word Reading
Imageability + Freq. List
All items 96 13 25 36 42 64 66 69 70 71 73 86 88
High Imageability 32 11 21 24 26 29 31 31 30 28 28 32 31
Low Imageability 32 0 1 3 4 15 14 14 17 20 16 28 26
PALPA 31
High Imageability 40 16 21 24 25 33 37 37 34 39 31 40 39 39.9 (39.4)
Low Imageability 40 0 2 1 13 18 27 26 27 32 27 37 39 39.5 (38.1)
2. Semantic Battery30 10 20 8 24 22 29 24 30 28 27 29 29
3. Monaghan &Ellis 2002
Consistent 36 3 4 9 25 29 28 27 24 25 27 32 36 35.8
Inconsistent 36 1 4 10 13 21 19 23 17 20 21 31 29 34.8
Max LR MM RJ RS AB NS MR BN TJ PG TH DB Controls Score (Normal cutoff)
Age(years) 58 58 40 64 83 51 72 52 60 66 48 61
Months postonset 156 120 18 31 14 96 28 42 68 28 31 6
4. PALPA part of speech
Total 80 3 7 17 30 57 47 66 70 64 58 74 79 79.7 (78.5)
Nouns 20 1 4 5 7 12 14 16 19 18 17 18 20
Verbs 20 1 1 6 13 17 12 17 18 17 13 19 19
Adjectives 20 1 2 3 5 14 14 17 18 14 16 20 20
Functors 20 0 0 3 5 14 7 16 15 15 12 17 20
5. PALPA 34
Morph complex 30 1 1 7 13 18 12 24 23 24 23 24 29
Non Word Reading
6. PALPA 36 24 2 0 2 8 13 7 8 11 2 9 6 14 22.9 (19.9)
Derived (2) 30 0 0 1 7 10 4 4 7 3 7 6 21 29.3 (27.4)
Derived (1a) 48 0 0 0 9 16 3 4 8 0 4 11 19 45.7 (42.9)
• There is a link between phonological and deep dyslexia
• Despite variation, there is overlap in dyslexic symptoms
• There is no sensible dividing line
• Deep dyslexia can be viewed as an extreme version of phonological dyslexia.
• Minimal evidence for symptom succession
Results & Discussion
2. Is phonological - deep dyslexia accompanied by phonological / semantic deficits?
• Reading deficit accompanied by impaired phonology in all cases
• As phonological tasks become more taxing, accuracy declines
• Insensitivity of word repetition to phonological impairment
• Reading deficit accompanied by impaired semantics in many cases
• Insensitivity of picture matching to semantic impairment
Results & Discussion
3. Can it be demonstrated that the degree of these impairments predicts the patients’ dyslexia symptoms?
Correlations of the four dyslexic symptoms against phonological and semantic measures
Imageability Effect Semantic Paralexias
Lexicality Effect Poor Nonword Reading
Correlation positive - as ph. skills diminish (effects reduce as ph. scores improve) Less positive - with better scores on synonym judgment
No correlation No correlation Correlation r=.56, p=.04 Strong – blending & segmentation Weak – other measures
Phonolo-gical skill
Correlation (effects increase with greater semantic deficit) No correlation with WPM or picture association task
Negative with synonym judgment (effects increase with greater semantic deficit)
Correlation Stronger as synonym judgment improved (effects diminish with increasing semantic impairment) No correlation with WPM or picture association task
No correlation Semantic skill
These findings suggest:
• Words are read correctly because activation of
phonology is boosted by their meaning
• If interaction is affected, semantic boost for word reading is diminished and reading accuracy reduces (vice versa)
• Negative correlations between semantic status and imageability effect/ semantic error suggest pathological semantic representations
• Performance of participants reflects a combination of impairments in the systems as well as in their interaction – consistent with the primary systems hypothesis
Results & Discussion
4. Can the symptoms associated with their reading deficits be elicited in nonreading tasks as the Primary Systems Hypothesis would predict?
Investigating the influence of delay on
repetition
Imageability Effect Lexicality Effect
a small but significant effect (p=.02)
a significant effect (p<.001)
Immediate repetition
a significant effect (p=.002)
a significant effect (p=.005)
Delayed Repetition
• Symptoms in the reading domain are found in
the nonreading tasks as well (repetition).
Research Questions 1. Is there a strong overlap between phonological and
deep dyslexia?
Yes
2. Is phonological - deep dyslexia accompanied by phonological and semantic deficits?
Yes
3. Can it be demonstrated that the degree of these impairments predicts the patients’ dyslexia symptoms?
Yes
4. Can the symptoms associated with their reading deficits be elicited in nonreading tasks as the Primary Systems Hypothesis would predict?
Yes
Summary of the relationship between acquired dyslexias
Limitations of Study
• Participants – individuals with mild or severe deficits were excluded.
• There was no information regarding what each participant was considered – phonological or deep dyslexic.
• No scanning images provided. Description of lesions for each participant could have provided valuable information
• Should be re-conducted longitudinally – checking recovery for each patient