The goal of the proposed research is to identify the areas of the brain that support the assignment of syntactic structure and the use of syntax to determine thematic roles using fMRI. The proposed research will test the hypothesis that the L IFG (Broca's area, BA 44 and 45, extending into 46/47) supports two aspects of the working memory system that is utilized during assignment of syntactic structure and interpretation of sentences - """"""""storage,"""""""" the storage of constituents in memory while they have yet to be assigned all their grammatical roles, and """"""""integration,"""""""" the assignment of thematic roles based on grammatical positions of noun phrases. We will test for the localization of these functions in two ways: using tasks that involve implicit syntactic and thematic processing, and using conjunction analyses in sets of tasks that involve explicit syntactic and thematic processing. We predict that increases in memory load (""""""""storage costs"""""""") and in computational load (""""""""integration costs"""""""") will lead to BOLD signal increases in L IFG in these tasks. The neural basis of syntactic processing is important to human health because syntactic structures are important to human communication. Syntax determines the relationships between words that allow sentences to convey information beyond what is conveyed by words alone (e.g., who is initiating an action, who receiving it, which adjectives are assigned to which nouns, and other relations between words). This propositional information is the source of much of the information stored in semantic memory, can be used in thinking logically, and serve the purpose of planning actions. Syntax allows the meanings of words to be combined in ways that do not correspond to likely events. This allows humans to think about possible events, not just react to events that have taken place or are likely to. The loss of the ability to use syntax to determine sentence meaning is thus a subtle but major problem for patients with stroke and other neurological diseases. By providing better information about what parts of the brain are involved in syntactic processing in normal individuals, this project will help clinicians identify patients at risk for such disorders, which can then be targeted in therapy.
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