SPCH3106 Lecture Notes - Lecture 5: Pure Alexia, Dyslexia, Grapheme
Module 5 Part 1 Reading & Writing
Written Communication – Background
• Orthographic language systems - word is basic unit
• Alphabet scripts
• “grapheme” = the letter or letters corresponding to a single phoneme
• Grapheme to phoneme conversion varies between language system
Reading – 3 routes
• Lexical semantic route : regular words, irregular words
• Lexical non-semantic : regular words, irregular words, but keeping in mind , this route
bypasses SS
• Non-lexical : regular words , non words
SO: Regular words – 3 routes irregular words -2 routes non-words – 1 route
Visual Orthographic Analysis
Two theories of pattern recognition:
1. Template matching – we have, stored in our brains , a template for all familiar patterns
2. Feature comparison – letters can be recognised in terms of distinctive features or common
elements ie, as combinations of vertical, horizontal, oblique and curved lines
The McClelland & Rumelhart Model (1981)
Interactive activation model of written word recognition.
Involves:
1. Feature detection
2. Abstract letter detection
3. Abstract word detection
VOA- helps us to recognise what we
are looking at are letters, not some
random blocks on page with no
linguistic code
Is there a representation in my OIL? Is it a
word or not a word?
Reading Disorders
5 main types:
• Visual alexia
• Pure alexia
• Surface alexia
• Deep alexia
• Phonological alexia
Visual Alexia
• Breakdown at the VOA
• Errors:
o Visually similar
Eg. Lend -> Land Calm -> claim
Pure Alexia (aka. Alexia without agraphia)
• Suggestion that impairment is in VOA and/or connection between VOA and OIL
• Letter by letter readers / letter naming eg. A-p-p-l-e
• Words/nonwords reading is very slow and effortful
• Reading time increases with word length
• No difficulties recognising spelled word or saying the word once it is recognised.
• Roughly 50% of patient with PURE ALEXIA also show characteristics of SURFACE DYSLEXIA
Surface Alexia
• VOA is intact, result of eficit in OIL
• May be required to use the non-lexical OTPC route to read words aloud.
• Can use non-lexical route to sound out words letter by letter
• What does this mean for :
o Regular words : should generally be okay, they can sound those words
o Irregular words: becomes problematic, because cannot be pronounces accurately
via non-lexical route
o Non-words: should be able to sound out word because non-lexical route is intact
o Pseudo-homophones: patients are sounding these words out from their non-lexical
route and think they sound like real-words. Basing on how these words sound
instead of how these words are actually spelt
*** need to gain access to OIL, to decide whether a word is real-word or not
• Frequency effects
• Length effects
• Errors:
o Regularisation errors: diseased -> deceased head -> heed steak-> steek
o Visual errors
o Misapplication of letter/sound rules eg. rage -> rag
Deep Alexia
• All the routes for reading are impaired.
Peripheral dyslexias
Central dyslexias
Document Summary
Written communication background: orthographic language systems - word is basic unit, alphabet scripts, grapheme to phoneme conversion varies between language system (cid:862)graphe(cid:373)e(cid:863) = the letter or letters (cid:272)orrespo(cid:374)di(cid:374)g to a si(cid:374)gle pho(cid:374)e(cid:373)e. Lexical semantic route : regular words, irregular words. Lexical non-semantic : regular words, irregular words, but keeping in mind , this route bypasses ss: non-lexical : regular words , non words. So: regular words 3 routes irregular words -2 routes non-words 1 route. Voa- helps us to recognise what we are looking at are letters, not some random blocks on page with no linguistic code. Involves: feature detection, abstract letter detection, abstract word detection. 5 main types: visual alexia, pure alexia, surface alexia, deep alexia, phonological alexia. Visual alexia: breakdown at the voa, errors, visually similar. Basing on how these words sound instead of how these words are actually spelt.
