M4, T2, Types of dyslexia and explaining dyslexia via word recog models

Question 1

Dyslexia

Answer 1

Dyslexia – reading deficit/problems
Acquired Dyslexia – reading problems and deficits due to brain injury or damage
Developmental Dyslexia – failing to meet age relevant reading standards with normal intellectual functioning and educational opportunities for reading

Question 2

Earliest cases of dyslexia

Answer 2

• Dejerine (1891) patient with dyslexia and dysgraphia, (i.e., deficit in reading and spelling/writing respectively) due to infarction in left parietal lobe
• Dejerine (1892) patient demonstrated a dissociation between reading and writing
• Patient could write well but could not read printed words aloud or for comprehension
• He could therefore not read things he had written

Question 3

Types of dyslexia

Answer 3

Peripheral dyslexias: affect early stages in word recognition
visual analysis of letters or words

Central dyslexias : affect deeper processes
- grapheme-phoneme conversion
- orthographic input lexicon
- semantic access

Question 4

Types of peripheral dyslexia

Answer 4

• neglect dyslexia
• pure alexia
• letter position dyslexia
• attentional dyslexia

Question 5

Neglect dyslexia, Brain (1941)

Answer 5

• Right hemisphere damage (parietal lobe) -> unilateral neglect
• Patient does not attend to left side of space

Neglect Dyslexia – described by Brain (1941)
- Neglect dyslexia patient does not read left/right half page or word (Haywood & Coltheart, 2000)
- Not a consequence of unilateral neglect, can co-occur with unilateral neglect
- Errors for reading printed words – failure to identify part of/portion of word, page of text

Question 6

Neglect dyslexia - examples

Answer 6

Neglect Dyslexia Left side
liquid -> squid
cage -> rage
yellow -> pillow

Neglect Dyslexia Right Side
book -> boot
milk -> mill
pen -> pet

Question 7

Neglect dyslexia - defining symptoms (errors)

Answer 7

• Errors are spatially determined visual errors consistently in left/right side of a word -> a neglect point in visual word reading
• All letters correct on preserved side
• Letters incorrect on the neglected side
• Errors – very similar to original word in length
• reading deficit occurs due to difficulty in specification of the word at the level of visual orthographic analysis

Question 8

Pure alexia

Answer 8

• Letter-by-Letter Reading or Alexia without Agraphia
• Writing and spelling unaffected
• Reading printed words is problematic
• Brain damage/lesion typically located inferior portions of occipital lobe bordering on temporal lobe in left hemisphere also damage to posterior portion of corpus callosum

Question 9

How pure alexia presents

Answer 9

• Can identify letters
• Reads words aloud - say one letter at a time – defining symptom
  CHAIR -> C…H…A…I…R -> “chair”
• Patient names (or misname) some or all of the letters before a response is made
• If patient can name all letters, then will correctly say word
• Response times increase as word length increases (e.g., 10 seconds per letter within a word)
• Occasionally patient can name short words without spelling e.g. ball
• Role of letter confusability in pure alexia reading ability
  X, J vs C, G, Q

Question 10

Pure alexia and the word recog model

Answer 10

• Brain damage results in problem with early visual processing letter features
• Impaired visual orthographic analysis
• Word information going to reading system is noisy

Question 11

Letter position dyslexia

Answer 11

• Primary error – letter transposition e.g., broad -> board
• Migration or transposition letters tend to be within word not initial or final letters
• Patient data Hebrew readers – lot of possible transposition words compared to English
• Correct letter identification but position coding of letters problematic
  jugde vs. judge
• deficit at visual orthographic analysis

Question 12

Attentional dyslexia

Answer 12

• Person can read a single letter or a single word in isolation but cannot read the same word or letter if it is shown with items of the same type
• Between-word letter migration errors – letter in one words appears within the other word
  -> Presented with WIN FED says FIN FED
  -> BFXQL asked to identify centre letter, says F or Q not X
• Problem with narrowing attention
• Deficit letter to word binding

Question 13

Attentional dyslexia - brain stuff and particular region of word recog model

Answer 13

• Exact location of brain lesion unknown but patients typically have damage to posterior left-hemisphere including subcortical structures
• Difficulty with the visual specification of the word at the visual orthographic analysis level

Question 14

Types of central dyslexia

Answer 14

• surface dyslexia
• phonological dyslexia
• direct-route dyslexia (lexical non-semantic reading)
• deep dyslexia

Question 15

Surface dyslexia

Answer 15

• Regular words read better than irregular words
  -> MINT FEAR VS PINT BEAR
• Preserved regular word and nonword reading
• Many patients worse at reading nonwords than matched real words
• Errors
  -> Regularisations (yacht, sew)

Question 16

Surface dyslexia - impaired pathways

Answer 16

• intact grapheme-phoneme conversion rules
• impairment of lexical route to reading aloud
  -> Orthographic Input Lexicon
  -> Orthographic Input Lexicon to Semantic System
  -> Orthographic Input Lexicon output to the Phonological Output Lexicon

Question 17

Phonological dyslexia

Answer 17

• Poor or flawed nonword reading
• Problems reading new words
• Nonwords might be read as visually similar words
  SOOF -> soot
• OK for well known (familiar) words
• Impaired sub-lexical (non-lexical) route to reading aloud

Question 18

Phonological dyslexia - impairment pathways

Answer 18

Impaired sub-lexical (non-lexical) route to reading aloud
-> impaired grapheme-phoneme conversion module
-> impaired access to the grapheme-phoneme conversion module
-> impaired output from the grapheme-phoneme conversion module to the phonological output buffer

Question 19

Phonological dyslexia - impaired grapheme-phoneme conversion module

Answer 19

• Non-word reading is non-existent
• Learning to read new words is non-existent via sounding out

Question 20

Phonological dyslexia - impaired (slowed) output from the grapheme-phoneme conversion module to the phonological output buffer

Answer 20

Some phonological dyslexics better at reading nonwords when these are pseudo-homophones (nonwords that sound like real words e.g. brane) than when they are non-words unlike a real word (e.g. frane)

Question 21

Phonological dyslexia - impaired input into grapheme-phoneme conversion

Answer 21

• Some non-words have one-to-one mapping between letters and sounds (graphemes and phonemes) e.g. trov
• Some non-words have a letter that must be combined to form a sounds (phoneme) e.g., thoo, which is graphemic parsing
• If there is a problem (noise) in the letter information coming into the Grapheme-Phoneme Conversion module phonological dyslexics will have more problems with non-words that need graphemic parsing

Question 22

Direct-route dyslexia

Answer 22

• also known as lexical-nonsemantic reading
• patient does not know the meaning of the word
• patient can still read printed irregular words aloud

Question 23

Deep dyslexia

Answer 23

• First systematic study – Marshall & Newcombe (1966)
• Typically an acquired reading impairment
• Cases of developmental Deep Dyslexia in the literature
• Defining symptom semantic error in reading aloud
• Symptoms of Deep Dyslexia typically unvarying across cases

Question 24

Deep dyslexia - symptoms when reading aloud

Answer 24

• Semantic errors
• Visual errors
• Visual-then-semantic errors
• Morphological errors
• Very poor non-word reading
• Imageability effect in reading words
• Content word reading better than function word reading
• Function word substitutions

Question 25

Deep dyslexia - semantic errors

Answer 25

Key symptom Tandem -> cycle Cost -> money Decay -> rubbish

Question 26

Deep dyslexia - visual errors

Answer 26

Visual errors Signal -> single Decree -> degree Visual-then-semantic errors Sympathy (symphony) -> orchestra Favour (flavour) -> taste Charter (chart) -> map

Question 27

Deep dyslexia - morphological errors and poor nonword reading

Answer 27

Morphological errors (derivational errors) Edition -> editor Courage -> courageous Very poor nonword reading (nonsense words) Wux -> don’t know Nol -> no idea

Question 28

Deep dyslexia - imageability effect

Answer 28

Better at reading concrete than abstract words - Better at saying 'butter' and 'windmill' than 'grief' and 'wish' - Errors abstract words -> visually related imageable words

Question 29

Deep dyslexia - content v function words

Answer 29

Content words (nouns, verbs, adjectives) Function words (was, quite, of) Function word errors Was -> with If -> yet Quite -> perhaps Yes -> small words are the worst

Question 30

Deep dyslexia - spelling and writing

Answer 30

- Spelling and writing may be impossible - If spelling and writing possible then symptoms are equivalent to those listed for reading printed words aloud - Majority of patients with deep dyslexia show all of these symptoms

Question 31

Explanations for deep dyslexia

Answer 31

Impairment(s) to the normal left hemisphere reading system through many different locations of damage OR Reading occurs via a secondary right hemisphere reading system

Question 32

Deep dyslexia and the left hemisphere reading model part 1

Answer 32

- Damage Grapheme-phoneme conversion– inability to read non-words - Damage Semantic System - semantic errors, and imageability effect - Damage Orthographic Input Lexicon- visual errors - Impaired connection between orthographic input lexicon and phonological output lexicon – poor word reading and function word errors

Question 33

Deep dyslexia and the left hemisphere reading model part 2

Answer 33

- Damage to connection between semantic system and phonological output lexicon – patient correctly understands a printed word but makes a semantic error reading it - Damage to component syntactic system processes prefixes and suffixes (morphological errors)

Question 34

Deep dyslexia and right hemisphere hypothesis

Answer 34

- If the left hemisphere cannot complete (orthography, semantics or phonology) then the right hemisphere reading system must take over -> Coltheart (1980, 2000) Deep Dyslexia is a loss access in the Orthographic Input Lexicon in the left hemisphere (cannot read printed words) Deep Dyslexic reads “words” - via Orthographic Input Lexicon in the Right Hemisphere - Activates semantic system representation in the Right Hemisphere - Information from Right Hemisphere semantic system sent to the Phonological Output Lexicon in the Left Hemisphere (needed to say word aloud) *look up image

Question 35

Explaining deep dyslexia errors via the right hemisphere reading

Answer 35

- Grapheme-Phoneme conversion non-existent in right hemisphere - nonword reading errors - Imageability effect - visual field studies show better performance for concrete than abstract words in right hemisphere - Semantic errors made in patients with no left hemisphere - Semantic errors may also result from incorrect target selection being transferred to left hemisphere or incomplete semantic word representation to start with - Function words are poorly represented within the right hemisphere

Question 36

Deep dyslexia and right hem reading, syntactic processing and visual errors

Answer 36

Syntactic processing in right hemisphere not as good as left hemisphere - morphological errors May also explain the visual errors – poorer word representation in right hemisphere and therefore visually close word is selected as target words

Question 37

Deep dyslexia relevant brain regions (Coltheart, 2000)

Answer 37

- Coltheart (2000) imaging study relevant areas include: - Orthographic processing – left occipital and occipitotemporal regions - Semantic processing – border between superior and middle temporal gyrus, areas BA21 and BA22 (Left Hemisphere) - Phonological output – left hemisphere frontal operculum *look up images (3)