Information processing of
reading
Geschwind’s disconnection:
isolation of visual regions from
language regions
Visual stimulus
DOG
PERIPHERAL
DOG
Visual analysis
4 legs, animal, bark
/dog/
Semantics/meaning
Pronunciation/phonology
CENTRAL
Visual Cognition
Pure alexia
Visual Cognition
Visual Word-Form Area (VWFA)
• Dejerine 1892
» alexia with agraphia
» alexia without agraphia
Visual Cognition
Petersen et al. (1992)
Devlin et al. (2006)
Visual Word-Form Area (VWFA)
Bilateral activation: VWFA
Vinckier et al. (2007)
McCandliss et al. (2003)
N170 waveform for letter strings
Experience dependence: VWFA
English readers
Bentin et al. (1999)
Hebrew readers
Baker et al. (2007)
Hallmark sequential reading
Maturation of VWFA
6000
5000
4000
al av
3000
c av
2000
1000
(6.4-11.6 yrs old)
0
Three Letters
Turkeltaub, Eden et al. (2008)
Pure alexic
Pure alexia
Impairment in word recognition in premorbidly literate adults
8000
Left occipitotemporal lesion
7000
−
No general language impairment
−
Rely on sequential “letter-by-letter” strategy
RT (ms)
−
9000
6000
DK
EL
MC
PA
PD
OL
468
810
5000
4000
•
−
Seven Letters
Visual Cognition
Lesions to VWFA

Five Letters
451
280
329
3000
2000
1000
12
0
3
4
Visual Cognition
5
6
Number of letters
7
8
Very surprising
Serial encoding
2000
• Patients can do lexical decision and make
semantic judgements at brief exposure
duration
EL
1800
Control BR
– Too brief for sequential processing to account for this
5th percentile BR
1600
RT (in msecs)
95th percentile BR
1400
• Even patients who can barely recognize
letters seem to do better at this
1200
1000
• Also show ‘higher order influences on
performance
800
1
2
3
4
5
– Right hemisphere output?
– Residual reading in normal system?
Serial position in string
Visual Cognition
Visual Cognition
Evident in eye movements too
Higher order effects?
controls high
controls low
12.5
hemianopics high
controls
hemianopics low
hemianopics
LBL high
LBL
LBL low
b. imageability
a. frequency
5
2.5
0
1
2
3
4
5
word length
6
7
8
12.5
12.5
10
10
number of fixations
7.5
number of fixations
number of fixations
10
7.5
5
5
2.5
2.5
0
0
short
Visual Cognition
7.5
long
word length
Visual Cognition
short
long
word length
Think Interactive Activation Model
Visual Cognition
Behrmann et al. (1998, Cog. Neuropsych.)
Plaut (1999, Cog. Sci.)
Domain generality
Linear effect of visual complexity
Pure alexia
Reaction Time (ms)
Visual Complexity
Same-different matching
+
Same/different matching
Linear effect: Words and Symbols
Therapeutic intervention
Visual Cognition
Black and white line drawings
Reducing serial position effects
3000
2500
MA
RT (in msecs)
DK
2000
IS
DS
MW - central
1500
MW - left
controls
1000
500
Low
High
Visual complexity
Visual Cognition
Visual Cognition
But still a letter-by-letter - alas
Impaired reading in “surface” dyslexia
• Brain damage to left temporal lobe (stroke, head injury, or degenerative disease)
in premorbidly literate adult
• Severe impairment to semantics, or to mapping from semantics to phonology
• Word reading accuracy influenced by frequency and consistency:
Patient
MP
KT
Correct Performance
HFR LFR HFE LFE
95
98
93
73
100
89
47
26
%Reg’s
90
85
NW
95.5
100
• Exception words produce regularization errors:
DEAF ⇒ “deef”
FLOOD ⇒ “flude”
SAID ⇒ “sayed”
GONE ⇒ “goan”
BROAD ⇒ “brode”
STEAK ⇒ “steek”
SHOE ⇒ “show”
SEW ⇒ “sue”
ONE
⇒ “own”
SOOT ⇒ “suit”
• Nonword reading accuracy is normal
• Word and nonword naming latencies are normal
Visual Cognition
Information processing of
reading
Deep dyslexia
• Inability to read pronounceable nonwords
• Error types in word reading
DOG
Visual stimulus
PERIPHERAL
DOG
Visual analysis
Semantic
Visual
Mixed Visual-and-Semantic
Visual-then-Semantic
Morphological/Derivational
Function-word Substitution
RIVER ⇒ “ocean”, CHEER ⇒ “laugh”
WAS ⇒ “saw”, SCANDAL ⇒ “sandals”
TROUBLE ⇒ “terrible”, JOLLY ⇒ “joy”
SYMPATHY ⇒ “orchestra”, via symphony
LOVELY ⇒ “loving”, NEARER ⇒ “near”
FOR ⇒ “and”, FROM ⇒ “with”
• Part-of-speech effects
4 legs, animal, bark
Semantics/meaning
nouns > adjectives > verbs > function-words
• Concreteness/imageability effects
concrete > abstract, abstract ⇒ visual errors
/dog/
Pronunciation/phonology
input, central, output
CENTRAL
Visual Cognition
• Subvarieties based on location of damage within semantic pathway
Dual-route theory of word reading
A connectionist framework for word reading
• Systematic spelling-sound knowledge takes the form of grapheme-phoneme
correspondence (GPC) rules (e.g., G ⇒ /g/, A E ⇒ /A/)
• Applying GPC rules produces correct pronunciations for regular words (GAVE)
and nonwords (MAVE), but incorrect pronunciations for exception words (HAVE)
• Exception words therefore require a separate lexical look-up procedure
Traditional “dual-route” model
of word reading
• Separate Semantic and Phonological pathways
• Entire system participates in processing all types of items
Connectionist framework for word reading
• Separate Semantic and Phonological
Coltheart et al. (2001, Psych. Rev.)
pathways
• Sublexical Route encodes systematic
• Entire system participates in
spelling-sound knowledge by GraphemePhoneme Correspondence (GPC) rules
processing all types of items
– Necessary for pronouncing novel
“pseudowords” (e.g., RINT)
• Lexical Route encodes whole-word
spelling-sound correspondences
– Necessary for overriding GPC
rules to pronounce “exception”
words (e.g., PINT)
• Semantic Route plays limited role
Surface dyslexia
• Normal pseudoword reading
• Regularize exception words
Phonological/Deep dyslexia
• Relatively intact word reading
• Very poor pseudoword reading