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Abstract:
Abstract: Recent neuroimaging studies comparing processing of
relative clause sentences of varying complexity suggest that left
pars opercularis and pars triangularis activations reflect
increased syntactic complexity (Just et al., 1996; Stromswold et
al., 1996; Caplan et al., 1999). It has been argued that increased
processing difficulty in relative clause sentences is not only
caused by complex integration processes, but is also partly due to
involvement of working memory processes such as maintaining active
unintegrated linguistic constituents (Gibson, 1998). In an
event-related 3T fMRI study (EPI, 8 axial slices, TR=1s, TE=30ms),
we dissociated these two aspects of sentence processing.
Participants read indirect German WH-questions varying on the
factors syntactic complexity (i.e., subject vs. object questions),
and syntactic working memory costs (i.e., short vs. long syntactic
movement of the interrogative pronoun in the object question).
Syntactic memory costs were correlated with significant activations
in a network comprising deep left pars opercularis (BA44) and left
superior pars opercularis, as well as four foci along the left
middle temporal gyrus. In the syntactic complexity contrast none of
these areas showed significant activations. Our data suggest that
Broca's area plays a role in syntactic working memory during
sentence processing. Moreover, they demonstrate that activations
observed in Broca's area can not be attributed to syntactic
complexity as such but must be dissociated from syntactic working
memory processes.
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