CALT Neurobiology of Reading and Dyslexia 5 — Questions and Answers
Question 1: Which gene has been most extensively linked to neuronal migration anomalies and susceptibility to dyslexia in GWAS and candidate gene studies?
- FOXP2
- DCDC2 (Correct answer)
- CNTNAP2
- SHANK3
Correct answer: DCDC2
DCDC2, located on chromosome 6p, is one of the most replicated dyslexia candidate genes and is thought to affect neuronal migration in reading-relevant cortical areas.
Question 2: Cortical ectopias and neuronal migration anomalies found post-mortem in brains of individuals with dyslexia are most densely concentrated in which region?
- Right frontal motor cortex
- Left perisylvian language regions (Correct answer)
- Bilateral occipital poles
- Right parietal-occipital junction
Correct answer: Left perisylvian language regions
Post-mortem studies by Galaburda and colleagues found microgyria and ectopias predominantly in left perisylvian regions critical for language and reading.
Question 3: Functional MRI studies comparing dyslexic and typical readers during rhyme judgment tasks most reliably show underactivation in which region?
- Left inferior frontal gyrus (Broca's area)
- Right superior temporal sulcus
- Left temporoparietal junction (Correct answer)
- Bilateral premotor cortex
Correct answer: Left temporoparietal junction
The left temporoparietal junction (including the angular gyrus and supramarginal gyrus) is consistently underactivated in dyslexic readers during phonological tasks like rhyme judgment.
Question 4: The 'dual-route' model of reading predicts that individuals with phonological dyslexia have a selective deficit in which reading pathway?
- Lexical-semantic route for irregular word reading
- Sublexical phonological route for nonword decoding (Correct answer)
- Direct visual route for whole-word recognition
- Orthographic route for high-frequency words
Correct answer: Sublexical phonological route for nonword decoding
Phonological dyslexia is characterized by a specific breakdown of the sublexical route, impairing the ability to decode unfamiliar words and pseudowords by letter-sound rules.
Question 5: Diffusion tensor imaging (DTI) studies most consistently reveal reduced fractional anisotropy in dyslexic readers within which white matter tract?
- Corticospinal tract
- Left arcuate fasciculus and superior longitudinal fasciculus (Correct answer)
- Cingulum bundle
- Right uncinate fasciculus
Correct answer: Left arcuate fasciculus and superior longitudinal fasciculus
Reduced fractional anisotropy—indicating less coherent white matter microstructure—is most reliably found in the left arcuate and superior longitudinal fasciculi in dyslexic readers.
Question 6: Neurobiological research on reading intervention outcomes in children with dyslexia has shown that effective phonological training can produce which type of brain change?
- Permanent structural thickening of the corpus callosum
- Increased activation in left hemisphere language regions approaching typical reader patterns (Correct answer)
- Selective strengthening of right occipital pathways only
- Reduction in overall cerebral blood flow during reading
Correct answer: Increased activation in left hemisphere language regions approaching typical reader patterns
Multiple neuroimaging studies show that successful phonological intervention in children with dyslexia produces increased left hemisphere activation that more closely resembles typical readers.
Question 7: The 'phonological core deficit' model proposes that the primary neurobiological impairment in dyslexia involves which specific process?
- Imprecise neural representation and manipulation of phonemes (Correct answer)
- Deficient visual processing of letter shapes
- Impaired working memory storage capacity
- Abnormal serotonergic modulation of attention
Correct answer: Imprecise neural representation and manipulation of phonemes
The phonological core deficit model, supported by extensive neuroscientific evidence, holds that dyslexia stems from imprecise or 'fuzzy' phonological representations at the neural level.
CALT Neurobiology of Reading and Dyslexia 5
Which gene has been most extensively linked to neuronal migration anomalies and susceptibility to dyslexia in GWAS and candidate gene studies?