Gloria Waters

Effects of Syntactic Structure and Propositional Number on Patterns of Regional Cerebral Blood Flow

Positron emission tomography (PET) was used to determine regional cerebral blood flow (rCBF) as a function of the syntactic form and propositional density of sentences. rCBF increased in the left pars opercularis, part of Brocas area, when subjects processed syntactically more complex sentences. There were no differences in rCBF in the perisylvian association cortex traditionally associated with language processing when subjects made plausibility judgments about sentences with two propositions as compared to sentences with one proposition, but rCBF increased in infero-posterior brain regions. These results suggest that there is a specialization of neural tissue in Brocas area for constructing aspects of the syntactic form of sentences to determine sentence meaning. They also suggest that this specialization is separate from the brain systems that are involved in utilizing the meaning of a sentence that has been understood to accomplish a task.

PET studies of syntactic processing with auditory sentence presentation.

Sixteen subjects made plausibility judgments regarding auditorily presented cleft object and cleft subject sentences (It was the actress that the award thrilled; It was the award that thrilled the actress). rCBF increased in Brocas area, pars triangularis, when subjects processed the syntactically more complex cleft object sentences. The results are consistent with previous experiments using written materials and suggest that an increase in rCBF in Brocas area is associated with processing syntactically more complex sentences.