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Abstract:
Asymmetry of the planum parietale area in the brain was
measured with magnetic resonance morphometry in 18 dyslexic
children compared with a control group, matched for age,
handedness, gender, and IQ. The planum parietale includes part of
the inferior parietal lobe. Planum parietale asymmtry was
correlated with performance on a phonological processing task
(dichotic listening to CV-syllables), and an attention shifting
task (Posner's cue-target task). The MR measurements were made on a
Siemens 1.5T scanner with a 3-D FLASH sequence, with 128 images.
Significantly more dyslexic subjects had an abnormal planum
parietale asymmetry. Overall, the dyslexic subjects performed worse
than the control subjects on both the phonological and attention
tasks. However, the dyslexic subjects with abnormal planum
parietale asymmetry were particularly impaired on the phonological
task, but performed within the normal range on the attention test.
In contrast, a subgroup with normal planum parietale asymmetry were
significantly impaired on the attention test, but performed within
the normal range on the phonological task. It is argued that
dyslexia may involve a subgroup of children with normal brain
asymmetry and phonological skills, but who has attentional deficits
that prevents them from developing normal reading habits.
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