unlocking the nature of the phonological–deep dyslexia ... · unlocking the nature of the...

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