Accumulation of paired helical filament tau contributes to neurodegeneration in Alzheimer's disease (AD). F-flortaucipir is a positron emission tomography (PET) radioligand sensitive to tau in AD, but its clinical utility will depend in part on its ability to predict cognitive symptoms in diverse dementia phenotypes associated with selective, regional uptake. We examined associations between F-flortaucipir and cognition in 14 mildly-impaired patients (12 with cerebrospinal fluid analytes consistent with AD pathology) who had amnestic (n = 5) and non-amnestic AD syndromes, including posterior cortical atrophy (PCA, n = 5) and logopenic-variant primary progressive aphasia (lvPPA, n = 4). Amnestic AD patients had deficits in memory; lvPPA in language; and both amnestic AD and PCA patients in visuospatial function. Associations with cognition were tested using sparse regression and compared to associations in anatomical regions-of-interest (ROIs). F-flortaucipir uptake was expected to show regionally-specific correlations with each domain. In multivariate analyses, uptake was elevated in neocortical areas specifically associated with amnestic and non-amnestic syndromes. Uptake in left anterior superior temporal gyrus accounted for 67% of the variance in language performance. Uptake in right lingual gyrus predicted 85% of the variance in visuospatial performance. Memory was predicted by uptake in right fusiform gyrus and cuneus as well as a cluster comprising right anterior hippocampus and amygdala; this eigenvector explained 57% of the variance in patients' scores. These results provide converging evidence for associations between F-flortaucipir uptake, tau pathology, and patients' cognitive symptoms.

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Tests of everyday action semantics were developed and piloted in a group of healthy adults (n = 53) and then administered to individuals with Alzheimer's disease (AD; n = 17) or Parkinson's disease dementia (PDD; n = 20). Relations between everyday action knowledge and everyday function were explored. Three action semantic tests were developed: Probe Test - 45 forced-choice questions regarding task sequences, objects, and steps; Picture Sequencing Test - sequential ordering of 4-5 cards depicting task steps; Script Test - open-ended verbal description of the steps required to complete everyday tasks. Cognitive tests, informant reports of functioning, and the Naturalistic Action Test (NAT), a performance-based test of function, also were administered to AD and PDD participants. NAT performance was scored for omission (failure to complete steps) and commission (inaccurate performance of step) errors. The AD and PDD groups performed worse than healthy participants on all action semantic tasks. AD and PDD groups significantly differed on only the Script Test - AD participants generated fewer correct steps. Performance on each of the action semantic tests significantly correlated with NAT omission errors. Only the Sequencing Test significantly predicted omissions, commissions, and informant report of everyday functioning. In sum, task knowledge is associated with omissions in everyday tasks and is impaired in both AD and PDD. The ability to accurately sequence task steps is associated with multiple aspects of everyday function and may be easily assessed with picture arrangement.

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