. Increased prefrontal activation in amyloid positive cognitively normal individuals during successful episodic memory encoding. Human Amyloid Imaging 2011 Meeting Abstracts. 2011 Jan 15;

Abstract:

Objective: To compare brain activation during successful memory encoding between young and old subjects, and to investigate relationships between brain activation and Abeta deposition within elderly subjects.

Methods: Twenty-six old subjects were scanned with PIB-PET and fMRI, and 14 young subjects underwent fMRI (mean age: young = 23.4[3.4]; old = 74.6[6.4]). Distribution volume ratios were extracted using Logan plotting and global PIB index values were used to classify old subjects into PIB+ and PIB- groups. During the fMRI task, 200 outdoor images were presented (4.4s each) and subjects indicated whether water was present. A post-scan recognition task with 100 foils was used to assess performance and sort data into 4 trial types (high confidence hits, low confidence hits, high/low confidence misses, and non-water response trials). Trial types were entered as covariates and contrast images between high confidence hits and misses were used in higher-level random effects models within each age group (p Results: Significant bilateral activation was present in lateral occipital/parietal, inferior temporal, parahippocampal/ fusiform and prefrontal cortices. Young subjects showed greater activation than old subjects across many posterior regions, and trends were present for reduced activation in PIB+ compared to PIB- old subjects. Furthermore, PIB+ subjects showed significantly increased prefrontal cortex (PFC) activation relative to PIB- subjects (young = PIB+ > PIB-).

Conclusions: These data extend previous work in aging by showing relationships between Abeta and brain activation during successful memory encoding. We found that increased PFC activation was specific to elderly subjects with high Abeta deposition, suggesting that preservation of the PFC may be necessary to remain cognitively normal in the presence of Abeta.

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