Although many investigators have reported that speech and language are affected in Alzheimer's disease (AD), the precise characterization of these abnormalities has proven difficult. The consensus is that semantics are profoundly disturbed with a relative preservation of syntax. Nonetheless, conflicting results have been obtained in studies attempting to identify the semantic problem in AD patients. The discovery of a consistent abnormality would aid in early diagnosis and differential diagnosis. A semantic marker could also be followed overtime and help to resolve questions of whether language abnormalities can be used to identify a subtype of AD patients with early onset and/or positive family history. The many studies investigating semantics of Ad have failed to consider the role of sentence accent in creating meaning. They have identified abnormalities of work retrieval fluency, but even these studies have not shown whether fluency is generally abnormal in AD patients (i.e., abnormal in more than one test) or whether such test abnormalities are related to abnormalities of conversational speech. The proposed study will focus on word-retrieval fluency and sentence accent in the speech of AD patients. We will use multiple tests of fluency to determine whether this defect is generalizable and to confirm that AD patients perform worse than normal controls. We will perform discourse analysis on speech samples from a semi-structured interview looking at the use of sentence accent for marking new and recoverable information in conversation. Normally, sentence accent helps to maintain the """"""""thread of a conversation"""""""" by indicating what material is new or important and therefore contributes to a sense of coherence in conversation. We expect that Ad patients will show abnormal cohesive use of sentence accent compared to controls. We have also designed a computer-assisted paradigm for testing the manipulation of sentence accent and the appropriateness of sentence accent in cued responses. We hop to identify a marker of the semantic abnormality in Ad speech that correlates with disease severity and helps to explain the impression of incoherent speech in these patients, as well as explaining some of the earlier inconsistent findings.
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