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Abstract:
Previous functional neuroimaging studies have not yet reached
agreement on the brain regions that are involved in phonological
processing. The discrepancies across studies may have resulted from
task differences or other aspects of experimental design. The
present study used functional magnetic resonance imaging to compare
three different phonological tasks in the same 12 individuals.
Three phonological tasks that are good predictors of reading skill
were used: (1) sound elision (SE), (2) word segmentation (WS), and
(3) rhyme judgement (RJ). Phonological tasks using real words were
contrasted to single word reading within the same functional run.
To avoid the acoustic scanner noise and to allow subjects to
generate overt responses to visually presented words, we employed a
"behavior interleaved gradient" technique during the acquisition of
whole-head fMRI data. Preliminary results revealed involvement of
inferior frontal, inferior parietal, and temporal areas. In
particular, the left posterior superior temporal region (posterior
to primary auditory cortex) was involved in all three tasks.
Comparisons among phonological tasks suggest that SE and WS
involved left inferior frontal regions more so than RJ. RJ, in
turn, engaged parietal and extrastriate areas more extensively than
WS and SE. Although these findings suggest a common neural
substrate for phonological processing among tasks that predict
reading skill, each phonological task also has a unique neural
signature dictated by both the phonological and cognitive demands
of the task.
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