Dyslexia Flashcards
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!!]
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!
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.
Define: Peripheral dyslexia
Deficit in the stages prior to dual routes (e.g., activating abstract letter identities in the graphemic buffer)
Define: Central dyslexia
Deficit in the dual-routes (lexical/non-lexical routes)
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.
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).
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.
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.
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.
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?”
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)
- Reading occurs via a secondary right hemisphere reading system
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
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)
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.
