Week 6- Dyslexia Flashcards
Levels of causation of developmental disorders
Etiology
Neurobiology
Cognition
Behaviour symptoms
Dyslexia
Specific learning disability
Difficulties in single word decoding unexpected in relation to age or other cognitive abilities and the provision of effective classroom instruction
Typically resulting from a deficit in the phonological component of language
Language based disorder of neurological origin
Single cause theory of dyslexia
Influences are one directional
Genetic-Neurobiological-Cognition-Behaviour
Phonological deficit hypothesis
Interactive model pf dyslexia
Structure and function of the brain are altered by experience
Genetic-Nerurobiological, cognition and behaviour (all affected by environment)
Multiple deficit model
Concordance rate in twins
Monozygotic: 68%
Fraternal: 38%
Familial risk of dyslexia
When one parent has it odds increase with a factor 7 to 12
Neurons of relevance to dyslexia
Pyramidal cells: Long output dendrite, typical in motor system
Magnocels: Many connections, involved in fast info processing
Ectopia
One cause of dyslexia
When cells migrate too far and are no longer involved in their neural network
Migration
Neurons migrate to outer levels
During gestation (7 to 11 weeks)
Cognitive factors of relevance
Phonological insights
Phonological skills can be tested with the Foneem-deletietest or with auditory discrimination/categorisation tests (POP vs KOP)
Auditory discrimintaion/categorisation test
Speech continuum is presented in which sounds gradually change
At-risk children show a less steep identification curve than control children- Indicating poorer phonemic categorization
Rapid Automized Naming Task
presented with sheet of colours and
objects and the goal is to rapidly retrieve and name the presented stimuli. Some
are more challenging (i.e., stroop variation
Cognitive level conclusion in dyslexia
Phonological knowledge/skill is a core ability
Severity of cognitive deficits and peoples environment determine their reading skill
Behavioural level of dyslexia
Reading skill as measured via speed and accuracy
Diagnosis of dyslexia
Purely behaviourally based (even though causative factors at other levels)
Persistent reading and spelling disorder
with a basis in neurobiological elements that can not be explained by other factors
Ellis and Young’s Dual Route Model
Model of processing that influences all language skills
Direct route for the processing of words you are familiar with- Analysed visually and proceeds to visual input lexicon
If not familiar proceeds to grapheme-phoneme conversion (primarily early readers)
orthography
Incongruence between graphemes and phonemes
The more inconsistent a languages orthography, the more difficult it is to acquire the spelling system of that language
Processing speed
The ability to perform simple, repetitive cognitive tasks quickly and fluently
Reaction and decision speed
The speed of making very simple decisions or judgements when items are presented one at a time
Psychomotor speed
Speed and fluidity with which physical body movements can be made
Schneider and Mcgrew
Hierarchy of speeded abilities
General speediness in Striatum III
Four Stratum II broad factors- Broad psychomotor speed, broad decision speed, broad cognitive speed, retrieval fluency
Speeded abilities are differentiated by:
-Degree of info processing needed
-Complexity of info being processed
-Characteristics of the stimulus being used
Split CHC factor of Long term storage and retrieval into:
-Learning efficiency
-Retrieval fluency
Neuroanatomy of processing speed
Slow processing speed associated with lower white matter volume (ApoF-e2 allele)
Increased gray matter improves processing speed (DCD2 allele)
Acculturation knwoledge
Comprehension knowledge
Neuroanatomy of semantic memory
Damage to medial temporal lobe
