OBJECTIVE: Differentially worse performance on category versus letter fluency suggests greater semantic versus retrieval difficulties. This discrepancy, combined with reduced episodic memory, has widespread clinical utility in diagnosing @entity195 ( @entity195 ). Our objective was to investigate whether changes in semantic processing, as measured by the discrepancy between category and letter fluency, was detectable in preclinical @entity195 : in clinically normal older adults with abnormal b-amyloid (Ab) deposition on positron emission tomography (PET) neuroimaging. METHOD: Clinically normal older adults (mean Mini Mental State Exam (MMSE) score = 29) were classified as Ab+ (n = 70) or Ab- (n = 205) using Pittsburgh Compound B-(PET) imaging. @entity1 completed letter fluency ( @entity24344 ; word generation to letters F-A-S) and @entity8408 ( @entity8408 ; word generation to animals, vegetables, fruits) annually (mean follow-up = 2.42 years). The effect of Ab status on fluency over time was examined using linear mixed models controlling for age, sex, and education. To dissociate effects related to semantic ( @entity8408 ) versus retrieval processes ( @entity8408 and @entity24344 ), we repeated models predicting @entity8408 over time, controlling for @entity24344 and likewise for @entity8408 controlling for @entity24344 . RESULTS: At baseline, the Ab+ group performed better on @entity24344 compared with the Ab- group but comparably on @entity8408 . Longitudinally, the Ab+ group demonstrated greater decline on @entity8408 compared with the Ab- group (p = .0011). This finding remained significant even when covarying for @entity24344 (p = .0107). Ab+ @entity1 similarly declined compared with Ab- @entity1 on @entity24344 (p = .0112), but this effect became insignificant when covarying for @entity8408 (p = .1607). CONCLUSION: These findings provide biomarker validation for the greater specificity of declines in category versus letter fluency to underlying @entity195 pathology. Our results also suggest that changes in semantic processing occur earlier in the @entity195 trajectory than previously hypothesized. (PsycINFO Database Record

Biomarker Validation of a Decline in Semantic Processing in Preclinical XXXX .

@entity1 :: ('9606', 'Species') :: ['participants', 'Participants'] @entity24344 :: ('MESH:C535950', 'Disease') :: ['FAS'] @entity8408 :: ('MESH:D013064', 'Disease') :: ['CAT', 'category fluency'] @entity195 :: ('MESH:D000544', 'Disease') :: ['AD', "Alzheimer's disease"]
@entity195 :: (MESH:D000544,Disease) :: ['Alzheimer's Disease']
