[W6] - CH17 Flashcards
The Neuroanatomical Circuitry of Reading
Dyslexic readers show two slower and more inefficient pathways compared to skilled readers, who have one quicker pathway for this.
Skilled readers activate the quicker, more rapid and automatic pathways to decipher words in print [VENTRAL STREAM - lower]
- Primarily situated in the posterior/back parts of the brain, along the interface
of the occipital and temporal lobes, in the fusiform gyrus.
- Processes words at the lexical level.
- Has further assistance from the insular cortex when automatically
processing unusual spellings of words
Dyslexics rely on different pathways [DORSAL STREAM - upper]
- Use compensatory mechanisms which are slower and less efficient, to
assist with word recognition skills
- Frontal activation
- Over rely on breaking down each word into its phonological core
The Parieto-Temporal System vs. the Occipito-Temporal Pathway
Parieto-temporal system: Essential for phonetic decoding in reading
- Initially analysing a word, pulling it apart by phonemes, and linking the
letters to sounds
- Angular gyrus and supramarginal gyrus are activated in this area
- Children learning to read initially use this system almost exclusively
Occipito-temporal pathway: Becomes more active as children become more
skilled at reading
- Insular cortex is involved in automatically recognizing words in print
and along with the occipito-temporal lobe, plays a key role in reading
fluency
- Uses a whole word approach to reading
- Words are automatically recognised by sight and don’t need to be
deconstructed phonetically in the parieto-temporal system
- When it is activated, an exact neural form of the word is retrieved along
with the words spelling, pronunciation and meaning
- Allows reading to become more fluent and automatic because
words are recalled quickly by sight rather than relying on
sounding out words every time.
[3rd pathway for phonemic decoding in Broca’s Area]
How the language disorders (aphasias) relate to reading abilities
Broca’s aphasia => good reading comprehension. Poor oral reading. Agrammatical speech equates to agrammatical writing. Failure to understand grammar when listening equates to failure to do so while reading.
Conduction aphasia => poor reading skills. Often make semantic paraphasia errors (saying synonyms for some of the words read) when reading aloud.
Transcortical sensory aphasia => reading aloud here is adequate. But poor reading comprehension.
The 4 General Subtypes of Reading Disorders
- Dysphonetic dyslexia
- Surface dyslexia
- Mixed dyslexia
- Reading comprehension deficits
Pure Alexia (word blindness/ alexia without agraphia)
Prevents a child from
reading.
- Caused by lesions in the visual pathways that prevent visual info from
reaching the extrastriate cortex within the occipital lobe - Cannot read but can recognise words spelled aloud to them, if word
was previously learned - Cannot use either the whole-word OR phonetic approaches because
they don’t get the initial visual information to process. - If child has previously learned to read and write and has acquired pure
alexia due to brain damage, the child will be able to write some words,
even in the absence of reading.
Dysphonetic Dyslexia (phonological dyslexia)
Reading disorder where a
person can read familiar words but has difficulty reading unfamiliar words or
pronounceable non-words.
- Phonological reading is required when a reader is presented with a
nonsense word or a new word that is not yet learned - Children with this disorder over-rely on memorizing whole words as they are
visualized in space because they CANNOT SOUND OUT (phonetically) the
word
Surface dyslexia (dyseidetic dyslexia)
Reading disorder where a person can
read words phonetically but has difficulty reading irregularly spelled words by
the whole-word method.
- ‘Surface’ is used because the error is made based on what the word
looks like on the “surface” rather than its meaning! - Usually caused by a lesion in the left angular gyrus
- Difficulty memorizing a whole word
- Characterized by an over-reliance on phonetically sounding out almost every word - which slows down reading fluency and can adversely affect reading
comprehension [i.e., they can read words that have regular spelling (bat, fist, chin) but have
difficulty reading words with irregular spelling (pint, yacht)]
Mixed Dyslexia (spelling/word-form)
Ability to read a word using a whole word
AND phonetic approach is disrupted, but visual pathways remain intact.
Individual letters can be recognized, so the word is read by reading these letters individually.
Direct Dyslexia
Language disorder caused by brain damage in which the
person can read words aloud without understanding them.
- Similar to transcortical sensory aphasia. The child can repeat what is said
to them but cant comprehend the meaning or produce meaningful
speech on their own (except words are written not spoken)
Semantic dyslexia/ Deep dyslexia
Making semantic errors during reading
- Rely on visual and semantic cues, while minimizing phonetic decoding
- Reading abstract words is difficult because of impaired phonetic
decoding and difficulty conjuring up a visual image of the word
Reading Achievement Items From the Neuropsychological
Processing Concerns Checklist for Children and Youth (NPCC-3)
Reading Decoding Difficulties:
* Over-relies on sounding out most words when reading; even familiar words.
* Over-relies on memorizing what words look like rather than
sounding them out.
* Substitutes words that sound like the target word (e.g., reading pear for bear).
* Substitutes words that mean the same as the word being read, but not the
word itself (e.g., reading truck for car)
Reading Comprehension Difficulties:
* Difficulty understanding what is read.
* Difficulty identifying main elements of a story.
* Appears distracted while reading.
* Misses important details while reading.
Attitudinal Issues:
* Avoids reading activities.
* Appears anxious/uptight/nervous while reading.
* Shows no interest in reading for information or pleasure.
Integrated SNP/CHC Model Classifications of Reading
Achievement
Broad:
Reading Achievement
Second-Order: (3)
- Reading Summary Indices.
- Basic Reading Skills.
- Reading Comprehension Skills.
Third-Order:
Basic Reading Skills =
- Phonological Decoding.
- Orthographic Coding.
- Morphological/syntactic Coding
Learning Disabilities Associated with Language Disorders
- Dysgraphia
- Dyslexia
- Oral Impairments
Subtypes of Dyslexic Dysgraphias
Dysphonetic Dysgraphia:
- Cannot sound out words and write them phonetically
- Phonetic decoding skills are impaired
- Supramarginal gyrus located at junction of temporal and parietal lobes is
affected
Surface/Orthographic Dysgraphia:
- Need to sound out words because they cant visually remember whole words
- Can spell regular words and write pronounceable nonsense words
- Angular gyrus plays an important role in the orthographic assembly of words.
Mixed Dysgraphia:
- Can copy written text and form letters correctly.
- Make phonological errors in spelling and orthographic errors based on faulty
sequential arrangement of letters.
- Left inferior parietal lobes interfacing with the temporal and occipital lobes and
angular and supramarginal gyrus are impaired.
Executive Dysgraphia:
- Involves the quality of the written product
- Poor organization and planning skills, lack of attention to proper grammar and
syntax, poor elaboration of details in writing.
- Includes cognitive functioning deficits which impact writing
Subtypes of Graphomotor Dysgraphias
Apraxia: Variety of motor skill deficits in which child has very little control over
skilled motor movement.
Development Coordination disorder (DCD): Brain regions impaired include Premotor cortex, supplemental motor cortex, basal
ganglia, cerebellum.
Developmental dyspraxia: Difficulty in the planning and execution of
a voluntary motor act. Brain regions impaired include Premotor cortex, supplemental motor cortex, motor
strip.
Ideomotor dyspraxia: Failure to carry out a motor act or gesture in response
to a verbal command. Brain regions impaired include Left superior frontal gyrus, Exner’s area, left
supplementary motor cortex area.
Ideational dysgraphia:
- Inability to perform a series of gestures due to a loss of plan of action for
movement
- Trouble planning a written assignment and organizing their thoughts in a
sequential manner
- Can perform motor acts in isolation but cannot string a series of motor acts
together (i.e., can write b alone but not in the word ball)
- Writing is slow, laborious and characterized by frequent erasures or self-
corrections.
- Brain region impaired: Left superior parietal lobe
Constructional Dyspraxia: Inability to construct/produce and/or regulate written language production due to deficits
with the Spatial Constraints of letter and word production
- Visual aspect of writing is a right-hemispheric function.
- Poor writing skills often related to failure to obey spatial constraints coupled
with a lack of consistency.
- Brain region impaired: Right posterior parietal lobe
