neural basis of reading Flashcards
writing system can be described in 2 dimensions
alphabetic vs logographic
transparent vs opaque orthography
transparent orthograph
1 to 1 mapping
each symbol = same sound
e.g., Italian and Kana
opaque orthography
no strict ways of saying each letter
e.g., English
Toy model steps
1) identify visual features
2) recognise as a letter
3) recognise word
4) know semantic meaning of word
is reaction time faster and more accurate for words or pseudowords
words
Support for toy model - Hulk et al (2006)
Ps asked word or non-word (lexical decision) ERPs calculated difference orthographic structure - 90ms word frequency - 110ms semantic coherence - 160ms
evidence against toy model
if was correct - would expect word recognition time to increase as word length increases - not the case
word superiority effect
can read words even when partially covered
top-down contributions
some knowledge of words stored (psychology = visual lexicon, neuroscience = visual word form area)
Monscieur C
stroke in fusiform area (Visual word form area)
could see letters but not recognise words
Visual Word Form Area (VWFA) - connections or more?
originally considered to be connections of neural fibres carrying info to and from occipital cortex
now considered more than just connections as strokes near by to not cause alexia - which they would if just connections
instead= specific part of word processing
Visual word form brain area
fusiform area
left occipital temporal ventral area
if VWFA only on left hemisphere
YES
Cohen et al (2002)
- presented visual stimuli to different hemifields (words, consonant strings and checkerboard)
- stimuli activated opposite visual cortex
- words activated left VWFA regardless of hemifield
split brain patients can’t process words in which hemisphere
LEFT
- when presented in right hemifield - left hemisphere can pass info to VWFA
- when presented in left hemidield - right hemisphere can pass info to VWFA
new name for VWFA
Prince and Delwin (2003)
- also active in naming objects, colours and pictures and when blind people read braille
- left ventral occipital area
VWFA - hierarchial progressive feature analysis
strongest > whole word forms > letter patterns > low- level features
explains why may be involved in other things
imagine visual word when name it?
pure alexia
damage to visual word form area
- word blindness
- can’t recognise words
- reading time directly proportional to length of word
- longer to recognise a and A as same letter
attentional dyslexia
damage to parietal lobe - involved in visuospatial attention
- difficulty separating constituent letters and words
- o = easier than bottle, bottle = easier than sentence
- letter migration error (Win Fed > Fin Fed) - can’t suppress
- intrusion of distractors - everything blurred
- attentional filter deficit - can’t suppress distractors
neglect dyslexia
damage to parietal lobe - involved in visuo-spatial attention
- letter substitution errors on one side - contralateral to lesion
- ignore one half of word - (Clock > block)
- spatial reference deficit
which dyslexia affects VWFA
pure alexia
which dyslexia affects visuo-spatial attention
attentional and neglect
peripheral dyslexia
difficulties in visual system rather than reading
- pure alexia, attentional dyslexia, neglect dyslexia
surface dyslexia
damage to pronunciation
- can read regular and non-words fine - difficulty with irregular
- problems with phonological or lexicon knowledge
- better with high frequency irregular words - but still bad
- damage to temporal lobe (speech processing takes place and phonological lexicon located)
phonological dyslexia
damage to GTP converter
- damage to posterior part of temporal lobe
- can read regular and irregular words better than non-words
- can’t do 1 to 1 mapping of letter to sound = no knowledge to help read non-words
- difficulty with rhyme judgement
- perceive words fine
deep dyslexia
damage to semantic memory and GTP converter
- can read regular and irregular words better than non-words
- semantic errors - say dog when read cat
- derivational errors - change verbs to nouns
- better at reading concrete than abstract nouns - semantic error
- damage to temporal lobe - especially anterior part (where semantic memory = stored)
