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Flashcards in Dyslexia Deck (38):
1

Describe the Dual-route Model

The dual-route model proposes that:

- The first stage of reading (pre-lexical/peripheral stages) involves (viewer-based) basic processing of visual features, identification of character shapes (Recognition that basic visual features for a shape), identification of letters (is it a letter? allographs - recognise various forms) and reference to abstract letter identities/graphemic buffer (which letter is it? word-based)

- Following the visual processing, the written text is processed via two separate channels.

1. The sub-lexical/non-lexical route involves grapheme to phoneme conversion and is used by skilled readers in pronouncing unfamiliar words, or invented non-words. It DOES NOT involved recognising a letter string as a word, but DOES involved reading words using letter-to-sound rules in a left to right serial process.

Graphemic buffer holds in mind information of a word that has already been processed while the rest is processed (e.g., hold C, A... while processing T).

2a. The lexical-semantic route - Recognises familiar letter strings as words (via lexical retrieval - like a dictionary). Also retrieves the meaning of familiar word (Semantic route). (orthographic lexicon -> Lexical semantics -> phonological lexicon) "Reading via meaning"

2b. The lexical non-semantic route - recognises familiar letter strings as words (orthographic lexicon --> phonological lexicon) and retrieves their pronunciation (Without meaning). Direct access of spoken word form, bypassing meaning. [THINK SEMANTIC DEMENTIA!!]

2

Describe the triangle model

The triangle model is relatively simple containing 3 primary modules and connections between them: orthography (written form), meaning (semantics) and phonological (spoken form). Suggesting that a combination of orthographic, semantic (and contextual) information leads to pronunciation.

It proposes that the same mechanism subsumes reading of both irregular and non-words; whereby orthographic and semantic components feed the selection of phonological units for both word-types.

The ‘phonological impairment’ account of phonological dyslexia is based on this model. It proposes that non-words are particularly susceptible to damage at the phonological level because they do not activate the semantic component or orthographic-to-semantic connections as strongly as known words do. It also argues that phonological dyslexia must occur in the context of a more general phonological impairment!

3

What are some of the advantages of the dual-route model over the triangle model?

The triangle model is simplistic and does not explain the different types of dyslexia very well. The dual-route model has greater explanatory power for the various dyslexia types.

4

Define: Peripheral dyslexia

Deficit in the stages prior to dual routes (e.g., activating abstract letter identities in the graphemic buffer)

5

Define: Central dyslexia

Deficit in the dual-routes (lexical/non-lexical routes)

6

Define: Attention dyslexia

(Peripheral OR central; location of lesion in the dual-route model; presentations & types of errors associated with this type)

A peripheral dyslexia characterized by a disruption in 'perceptual grouping' whereby intact single word-reading, yet migration of letters between words (e.g., POT BIG HUT -> but, big, hut).

Knowing which letters go together with each word.

The current dual-route model does not account for this type - as the model deals mainly with single words.

7

Define: Letter-position dyslexia

(Peripheral OR central; location of lesion in the dual-route model; presentations & types of errors associated with this type)

Peripheral Dyslexia - Mis-ordering letters resulting in reading as a word with the same letters but in a different order.

More apparent in Hebrew as more 'migrate-able word'. Whereas in English, few migratable words, often able to read words even if unsure of letter order (e.g., elttr odrer).

8

Define: Neglect dyslexia

(Peripheral OR central; location of lesion in the dual-route model; presentations & types of errors associated with this type)

Peripheral dyslexia - 'neglect' = make errors on one side of words.

Can be stimulus-based (left or right side of a word) e.g., Quick -> quiet (and on the left OR right side of a word written backwards) [ prior to canonical representation]

Can be word-based: beginning/end (and at the beg or end of a word written backwards!) [allograph + level - word represented in canonical form]

Can co-occur with visual-spatial neglect. BUT NOT necessarily, can be reading specific.

9

Define: Phonological dyslexia

(Peripheral OR central; location of lesion in the dual-route model; presentations & types of errors associated with this type)

Central dyslexia - an impairment to the sub-lexical route. Familiar words are read better than unfamiliar words (or non-words).

Errors: tend to read non-words as a word that looks similar. e.g., cobe --> "Comb"
Can often name letters (B = bee), but not the letter sounds (B = Buh). Poor reading of 'less common' words (Susceptible to loss).

NOTE
Can be due to general phonological impairment (As proposed also by the triangle model!) But, can also be reading-specific.

10

Define: Surface dyslexia

(Peripheral OR central; location of lesion in the dual-route model; presentations & types of errors associated with this type)

Central dyslexia - damage to the lexical route. Unable reading irregular words.

Errors: 'regularisation errors' - Yacht --> Yatched (trying to use letter-to-sound rules). and this can lead to miscomprehensions (come -> kome -> kome your hair!) ERRORS reflect an over-reliance on non-lexical route due to impairment of lexical processes.

11

Define: non-semantic reading

(Peripheral OR central; location of lesion in the dual-route model; presentations & types of errors associated with this type)

A Central dyslexia - a semantic impairment - able to read aloud both regular and irregular words, but poor word comprehension. Unable to access semantic system.

Hyena -> "hyena, what the heck is that?"

12

Define: Deep dyslexia

(Peripheral OR central; location of lesion in the dual-route model; presentations & types of errors associated with this type)

Central (in theory), does not fit well within the dual-route model. (Theorized that both routes impaired)

ERRORS
- Unable/very impaired to read non-words
- [KEY FEATURE] makes semantic errors in reading single words (tandem -> cycle; cost -> money)
- Visual errors (Signal -> single; decree -> degree)
- Imageability affect / poor functor words.

Also:
- Visual-then-semantic errors (Sympathy -> orchestra; favour --> taste)
- Semantic errors also evident in spelling
- better reading of concrete than abstract nouns ('imageability effect")
- Poor at reading functor words.

Often arises when there is a large lesion.


THEORIES
1. Impairment to normal (left hemisphere) reading system (if so, then must have multiple impairments)

2. Reading occurs via a secondary right hemisphere reading system

13

Describe the 'errors' and dissociation (e.g., reading versus oral tasks) that are likely to be evident when the Character Shapes component of the dual-route model is damaged.

Basic processing of 'shape' clusters (e.g., components, such as a curved line, recognized as a shape)

IMPAIRED
- Also affects visual-processing of pictures
- If neglect is present, will be stimulus-bound (to each word)

ABLE
- Can do oral spelling

14

Localise the lesion Case 1:

IMPAIRED
- reading (80%)
- makes errors in letter identification (confusing 'd' and 'b', incorrectly identifying letters, particularly at the end of words e.g., sailor -> sailog)
- Poor visually cued word retrieval (sgF -> Fancy)

ABLE:
- Copy pseudoletters
- letter decision (Identify real letters versus non-letters)
- Recognition of oral spelling

LESION: Connectivity between allographs (identifying that something is a letter) and graphemic buffer/abstract letter identity (what letter is it, and holding this info in mind while processing other letters).

INTACT
- Basic visual features processing
- Character shapes visual processing
- Allographs (able to recognise it IS a letter, but not which one)
- Dual-route (central) processes (recognition of oral spelling)


15

If a child cannot read due to a sensory deficit or lack of learning oppourtunity (i.e., instructional casualty) - would this be termed a 'developmental dyslexia'?

No. Developmental dyslexia is difficulty acquiring reading skills normally. NOT due to a sensory deficit or instructional casualty.

16

Describe the process of acquiring the dual-route reading model (i.e., the development of reading)

1. Learn letters (visual forms)
2a. Learn letter-sound rules (phonics) B -> 'buh' starting with basic letters and then more complex rules
2b. Build Orthographic lexicon (irregular spelled and sight words)

Continues all your life!

17

Describe the three distinct functions that occur in the peripheral stages of reading.

* Identifies the abstract identity of letters [substages include: basic feature processing, visual letter representations first, allographs (is it a letter or not) followed by abstract letter identities! - letter names and sounds are accessed through abstract letter identities! [CASE ET])

* Encodes their position within the word

* when more than a single word is read, sets the attentional window that allows attention to be allocated to a single word (' letter to word binding' so letters don't get mixed up between words, keep track of separate words!)

18

Define: Letter ID dyslexia

(Common errors?, how would you test for it? can it be treated?)

Deficit in accessing abstract letter identities (can't identify letters, when spoken or read)

* Characterised by letter substitutions and omissions e.g., Cat - "Cap" (but need to check it isn't a misunderstanding of letter-to-sound words!).

CAUTION: this is also a normal stage in the development of reading! Most children go through this stage.

[Test it]:
- case matching (can they match upper and lower case letters).
- Letter/number decision (can they identify which are the real letters - i.e., test allographs)
- Psuedoletter copying (ensure it is not difficulty with basic feature mapping)

Treating with teaching of letter identifies and sounds -> quiet successfull! THEREFORE, intensive training (e.g., 'letter land') can lead to improvements.


[CASE: ET]
* 7 year old boy
*poor at naming letters (6/26 lower, 7/26 upper)
* poor at giving letter sounds (5/26 lower)
* poor at letter writing (5/26 lower, 3/26 upper)
* UNABLE TO MATCH uppercase and lowercase (46%)
THEREFORE, hasn't acquired abstract letter identities (CAN'T tell A and a are the same letter)

19

Define: Letter position dyslexia

(Common errors? how would you test for it?)

Deficit in processing letter order, but normal processing of abstract letter identities. i.e. mixing up letter order! (more easily noticed in Hebrew due to high numbers of migratable words!)

[Common errors:]
*Transposition of letters within a word e.g., tired -> tried
*Normal on MOST tests of single word/non-word reading (unless you have a specific list designed to pick up transposition errors!! i.e., migratable words)
*Spelling is often poor
*Often parent/teacher concern picks up on these kids.

[Test it]:
- migratable (anagram LetPos on motif) words e.g., trail/trial (where the letters, when rearranged, could make another valid word!)





Note that normal readers make few errors on migratable words!. Normal readers make few errors (4 transposition, 2 word errors 1 non-word error) of these words - LPD may make transposition errors on nearly all migratable words!

20

Define: Attentional Dyslexia (developmental)

(Common errors? How would you test for it? Treatment?)

When reading more than a single word (sentences or word pairs) letters migrate between words e.g., fig tree -> fig free.

[Error profile:]
*Single word reading normal
*Letters migrate between words (sentences or word pairs)
*Identifies individual letters ok! (can recognise A and case match A-a)

Test it:
- Can match case (abstract letter IDs ok)
- Can identify real vs fake letters (allographs ok)
- Single word versus word-pair

[Treatment:] A little cut out window can be used to help attend to only one word at a time!

21

Why are 'clean' cases of central dyslexias difficulty to find in developmental dyslexia?

(i.e., more likely to find 'mixed' lexical/sub-lexical, dyslexia?)

Because the stages of reading are developing together and depend on each other to some extend - you often find difficulties in both the lexical and sub-lexical routes.

e.g., difficulty with letter-to-sound rules may impede acquisition into the lexical. ...It may also lead to similar errors in spelling! - so may also present with spelling difficulties. [but there is lots of debate about whether lexicons are shared etc]

HOWEVER, there are cases where children do present with a 'pure' phonological or surface dyslexia.

22

LF, a yound boy, has particular difficulty reading irregular words outloud indicative of a 'surface dyslexia'. Additional investigations indicated that his deficit isn't just in reading words aloud, he also has difficulty:

Determine which of two same-sounding written words meets a certain criteria e.g., which is the vegetable? Been or Bean

And has difficulty identifying which is a real-word from words that would sound alike (lexical decision): e.g., which is a word 'worry, wurry, warry'

Based on this information, localise the deficit to a specific module in the lexical route.

The difficulty on written (non-verbal tasks) suggests that the task IS NOT just related to phonological ouput i.e., it must be earlier.

Difficulty in the first task (which is the vegetable) requires semantics. (i.e., errors must be here or earlier!) [#this could also be tested using other non-reading semantic tasks like picture naming!!)

Difficulty in the second task (lexical decision) require the orthographic input lexicon. (i.e., 'which of these written words is in my lexicon?)

This suggests that the issue is that he hasn't acquired all the words he needs in his ORTHOGRAPHIC INPUT LEXICON!

23

a 13 YO girl with a reading age of 6, demonstrated semantic errors in single word reading ('boy -> man; clock -> watch) as well as:
*difficulty reading non-words
*poor at function words
*shows effects of imageability

What might be the developmental dyslexia present here?

Authors suggested it was a 'developmental deep dyslexia'.

Authors suggested this may have been due to a failure of sub-lexical route, reliance on lexical-route which was also flawed.

24

SUMMARY

In developmental dyslxia, how would you test for (Also expected errors):

0. Issue with abstract letter identification
1. Letter position dyslexia?
2. Attentional dyslexia
3. Phonological dyslexia
4. Surface dyslexia (And its components!)
5. deep dyslexia

0. Abstract letter IDs: Case-matching (A-a), also substituion errors 'Cat' read as 'Cap' (poor letter ID, but be careful as may also be a phonological error!)

1. Letter position: Migratable words

2. Attentional: Word pairs (they are ok on single words), also look for errors where letters migrating between words with good single word reading.

3. Phonological: Nonwords (can also test letter-sound knowledge! B -> Buh; and blending C-A-T -> CAT)

4. Surface: Irregular words, lexical decision (can identify real vs fake written words), semantics (picture or word semantic matching), spoken word-production to pictures also look for regulisation errors (reading the way a word looks, suggest reliance on sub-lexical route)

5. Deep: both irregular and non-words, but particularly function words (and if ; low imagenability); also look for semantic errors (man -> boy)

25

What is the MAIN problem when trying to identify the 'cause' of dyslexia?

Dyslexia is not ONE THING. It is unlikely that 'one thing' is the underlying cause for every variety of dyslexia.

26

In regards to the 'cause/s' of various dyslexias, what is a proximal cause? and what is a distal cause?

Proximal cause: part of cognitive system responsible for performance (localisation within cognitive model) - arguably most important for treatment!

Distal cause: Factor involved in developement of current state of systme (how/why did it come to be this way?)

27

Describe the 'phonological awareness (and auditory temporal processing) hypothesis of phonological dyslexia

The theory that some cases of phonological dyslexia (difficulty readining non-words/with letter-sound rules) is underlined by a general difficulty in phonological awareness and/or temporal processing.

Unlikely to be true for ALL dyslexias, or ALL phonological dyslexias!.



#additional notes:
It is not clear whether phonological awareness leads to good reading (E.g., drop in phonological awareness in normal children when first learning how to read). On the other hand, there is some evidence that early awareness of phonemes is particularly predicitve of later reading skill. (unsure whether letter-sound rules help phonological awareness or vice versa!)

[how might auditory temporal processing lead to phonological dyslexia]:
Auditory temporal processing (difficulty with rapid temporal processing, possible due to a cellular difference) might lead to subtle speech perception difficulties --> phonological awarness deficit --> poor non-lexical skills (phonological dyslexia).

e.g., study: Auditory temporal processing - poor readers asked to discriminate sequences of tones e.g., high low/low high; they were the same as controls at slower rates, much worse at rapid rates THEREFORE ? deficit in rapid temporal processing!

CAUTION: when children are around school age they often have good phonological awareness, then learning to read can result in a change/reduction in their performance on phonological awareness tasks (corruption) e.g., pitch/rich

28

What is phonological awareness?

Phonological awareness is knowledge of sound rules and affects spoken language!:
*Take the /K/ sound for CAT (phonmeme deletion)
*What rhymes with POT? (rhyme)
*say the sounds of SKIN in reverse (reversal)
* What does /t/, /i/, /p/ say? (blending)
* Say the syllables of PENCIL. (syllabification)

29

Do children (Developmental) with surface dyslexia usually show deficit in phonological awareness?

Not usually.

30

What are some of the proposed causes of developmental surface dyslexia? (3 theories)

1. Visual memory deficit - perhaps the children are not remembering the visual representations of the words (and not building a lexicon) - but mixed evidence! (some evidence in difficulty recall of visual patterns, but others not!)

2. Verbal working memory - ability to hold and manipulate items in memory for a short time. Hypothesized to be required for storing and blending letter sounds into words - BUT improving WM does not seem to improve dyslexia.

3. ?Attention - possible link between ADHD and dyslexia (commonly co-occur) - HOWEVER, study found double dissociations found between attention deficits and dyslexia, suggesting these are independant skills.

31

Briefly outline the evidence that dyslexia has a genetic component.

When comparing twins, reading problems more likley to co-occur in identifcal twins (versus fraternal) and MORE co-occurance for phonological dyslexia.

Parent with dyslexia increases risk for child, unclear precisely why.

Lots of work still to be done in this area!!

32

Summarise the proposed causes for developmenta 'phonological' and 'surface' dyslexia.

Developmental phonological dyslexia tends to show
- subtle auditory deficits
- language processing deficits
- strong genetic influence

Developmental surface dyslexia tends to show
- no clear associated deficits across group
- delay pattern (still acquire some over time)
- Lower genetic influence

33

How might you test the phonological output?

If it is deficient there will be a spoken language deficit. (think of it as the phonological loop - test with repetition)

Test with non-word repetition and look for length effects.

34

How would you treat letter ID dyslexia?

Treat with practice of letter identifications - e.g., letter lands "Hi I am Harry Hat Man...."

35

How would you treat letter position coding?

Finger tracking
Treating associated spelling difficulties (if present)

36

How would you treat lexical processing?

Practice of sight word recognition (increase the lexicon)

37

How would you treat non-lexical processing?

Phonics approach (E.g., jolly phonics, multilit, understanding minds program)

38

How would you treat poor comprehension?

Practice via spoken language
- vocabulary
- reciprocal teaching (clarify, summarise, predict, question generation).
- visualising verbalising