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Abstract:
Previous research suggests two anatomical reading disability
phenotypes: one for phonological deficit (PD) and one for
comprehension deficits (CD). College students with PD had marked
cerebral and cerebellar asymmetries and duplications of
Heschlís gyrus, while college students with CD tended to
have relatively smaller symmetrical hemispheres and plana. Children
with oral receptive language impairment (LI) share anatomical
characteristics with CD. When seven anatomical measures of brain
size and asymmetry were weighted and combined into one anatomical
risk factor score for 170 adults and children, 67% PD students fell
in the bottom quartile (anatomical PD phenotype) while 75% CD and
67% LI students fell in the top quartile (anatomical LI phenotype).
In a new sample of 22 children receiving reading remediation, the
10 children with an anatomical LI phenotype had severe receptive
language impairments (CELFIII: 69 +/- 18). The 12 remaining
children had significantly higher oral language (p < .001) and
reading scores (p < .05). Only 3 of these 12 had an anatomical
PD phenotype. We speculate that small symmetrical cortical maps are
a risk factor for poor receptive language. Marked asymmetries and
duplicated gyri may allow the development of protective lateralized
cortical specialization but increase the risk for mismatched
auditory, visual and motor maps and phonological deficits. Reading
disorders with different anatomical phenotypes may have different
etiologies. (R01s DC2922 & HD36461).
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