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Abstract:
The Words-and-Rules theory (WR) posits that different mental
processes underlie regular and irregular past tense formation:
regular forms are rule-generated (add -ed), whereas irregular forms
are retrieved from memory. These mental processes are hypothesized
to engage distinct neural mechanisms. The goal of the present study
was to localize and differentiate the neural substrates of regular
and irregular past tense generation. 16 normal right-handed native
English speakers underwent event-related fMRI. Subjects viewed
regular and irregular verb stems and responded covertly, either
reading the stem or producing its past tense form. Random effects
analysis revealed that past tense generation relative to stem
reading for regular verbs elicited greater activation in the
posterior extent of the left Inferior Frontal Gyrus (IFG), BA 44.
For irregular verbs, this comparison revealed differential
responses in the left IFG, BA 44/45, and the left Middle Frontal
Gyrus, BA 9/46. These results are consistent with a version of WR
that posits frontal lobe activity during both application and
inhibition of a rule. Specifically, BA 44 activity may correspond
with application of the affixation rule, whereas BA 9/46 activity
may correspond with its inhibition. BA 44/45, which has been
implicated in selectional processes, may reflect selection of the
appropriate irregular past tense form among memorized
alternatives.
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