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IC‐P‐087: Antisaccades in Alzheimer's disease using fMRI
Author(s) -
Wright Sarah,
MacAskill Michael
Publication year - 2012
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2012.05.120
Subject(s) - antisaccade task , saccade , psychology , intraparietal sulcus , frontal eye fields , neuroscience , prefrontal cortex , eye movement , dorsolateral prefrontal cortex , posterior parietal cortex , neuropsychology , saccadic masking , cognition , functional magnetic resonance imaging , audiology , cognitive psychology , medicine
Background: Alzheimer’s disease (AD) with early onset often presents with a distinct cognitive profile, potentially reflecting a different distribution of underlying neuropathology. The purpose of this study was to examine the relationships between age and both in vivo fibrillary amyloid deposition and glucose metabolism in AD. Methods: Dynamic [11C] Pittsburgh compound-B (PIB) (90 minutes) and static [18F]fluorodeoxyglucose (FDG) (15 minutes) scans were obtained in 100 AD patients and 20 healthy controls. Parametric non-displaceable binding potential images of [11C]PIB and standardized uptake value ratio images of [18F]FDG were generated using cerebellar grey matter as reference tissue. Nine [11C]PIB negative patients were excluded. The remaining patients were categorized into younger (n 1⁄4 45, age: 56 6 4) and older (n 1⁄4 46, age: 69 6 5) groups, based on the median age (62) at time-of-diagnosis. Results: Younger patients showed more severe impairment on visuo-spatial function, attention and executive function composite scores (P <0.05), while we found a trend towards poorer memory performance for older patients (P 1⁄4 0.11). Repeated measures ANOVA showed no main effect of age for [C]PIB or [F]FDG, suggesting that overall, the extent of amyloid deposition or glucose hypometabolism did not differ between groups. Regional distributions of [C]PIB and [F]FDG (both p for interaction<0.05) differed between groups, however, largely due to increased [C]PIB binding and decreased [F]FDG uptake in the parietal cortex of younger patients (both P <0.05). Linear regression analyses showed negative associations between visuo-spatial functioning and parietal [C] Pittsburgh compound-B binding for younger patients (standardized b: -0.37) and between visuo-spatial functioning and occipital binding for older patients (standardized b: -0.39). For [F]fluorodeoxyglucose, associations were found between parietal uptake with visuo-spatial (standardized b: 0.55), attention (standardized b: 0.39) and executive functioning (standardized b: 0.37) in younger patients, and between posterior cingulate uptake and memory in older patients (standardized b: 0.41, all P <0.05). Conclusions: These in vivo findings suggest that clinical differences between younger and older AD patients are not restricted to topographical differentiation in downstream processes, but may originate from distinctive distributions of early upstream events. As such, increased amyloid burden, together with metabolic dysfunction, in the parietal lobe of younger AD patients may contribute to the distinct cognitive profile in these patients.