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Abstract:
Electrocortical event-related potential studies have shown
topographically-distinct, temporally-restricted activation
depending on the specific sentence agreement. We investigated the
contribution of left inferior frontal (IFC) and left
posterior-superior temporal regions (PSTC) in syntactic and
semantic components of sentence agreements with event-related BOLD
fMRI in 13 young healthy right-handed subjects. Half of the
randomly ordered sentences were coherent and half contained
violations, equally divided among phrase structure, morphology,
verb subcategorization and semantic (selection restriction)
agreements. Subjects completed five runs of sentences by pressing
one button when an error was detected, and another button at a
sentence-terminal prompt if no error was detected. A random-effects
analysis was conducted with SPM windowed temporally to monitor
brain activation at early and late points following an agreement.
Only correct judgments were considered. Soon after
subcategorization violations, left IFC, left angular gyrus,
bilateral medial frontal, and right insula were recruited; later
activation included only frontal regions. Morphological violations
elicited bilateral medial frontal and right IFC early, but later
recruited left IFC. For phrase structure violations, medial and IFC
involvement was bilateral during both time windows. Morphological
and phrase structure violations additionally recruited left PSTC
over both time windows. Semantic violations also maintained left
PTSC and bilateral medial frontal activation during both time
windows. The neural basis for grammatical violations is
heterogeneous anatomically and temporally.
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