| |
Abstract:
This paper reports a series of studies of syntactic
processing using positron emission tomography (PET) and event
related functional magnetic resonance imaging (er-fMRI). In all
experiments, we used a plausibility judgment task and contrasted
hemodynamic responses to sentences with more complex sentence
structures with responses to sentences with less complex syntactic
structures. Using PET, we found that regional cerebral blood flow
(rCBF) increased in Broca's area in young adults when the syntactic
differences pertained to the complexity of relative clause
structures (object vs subject relativized stuctures). This brain
region remained active in young adults when subjects made these
judgments with concurrent articulation to impede rehearsal. A
second syntactic contrast -- passive vs active structure -- did not
result in reliable increases in rCBF. In elderly subjects, the
contrast involving relative clauses led to activation in the
inferior parietal lobe. In many studies, midline frontal structures
also increased their blood flow. Using er-fMRI, we presented
sentences in slow RSVP form. We found that blood oxygenation level
dependent signal (BOLD signal) increased in the temporo-parietal
junction in young adults for plausible object- compared to
subject-relativized sentences at a time point that corresponds to
their viewing the relative clause. The results across all
experiments suggest that either task demands or subject factors
make for differences in the regions that show hemodynamic responses
to processing more complex syntactic structures
|
