P2–127: Is verbal episodic memory in elderly individuals with amyloid deposits preserved through altered neuronal function?

Approximately 30% of the elderly come to autopsy with significant cerebral amyloid pathology but the mechanisms that enable intellectual preservation in individuals supposedly on the path to ADare not yet fully understood. In the present study we explored the inter-relationships between amyloid deposition, glucose metabolism and cognitive performance in 81 cognitively normal elderly (mean age: 75 ± 7, MMSE: 29 ± 1). Subjects were divided into low-amyloid (n=53), intermediate-amyloid (n=13) and high-amyloid (n=15) groups as defined by their [11 C]PIB status. To assess glucose metabolism in highly vulnerable AD regions, pons normalized standardized uptake value ratios of [18 F]FDG images we extractedusing a MetaROI mask that includes theposterior cingulate cortexand bilateral angular and inferior temporal gyri . Previously validated factor scores for verbal and visual episodic memory, semantic memory, working memory and executive functioning were used to evaluate cognitive performance in detail. Linear regression analysis, adjusted for age, education and APOE, showed an association between precuneus [11 C]PIB retention and compositie MetaROI [18 F]FDG uptake at trend level (b: 0.21, p=0.10)that became significant after additional adjustment for cortical gray matter volume (b: 0.28, p<0.05). Precuneus [11 C]PIB was negatively correlated with visual episodic memory (b: -0.30, p<0.05), but this finding did not survive adjustment for age, education and APOE genotype. Across all subjects, composite and regional [18 F]FDG uptake were not associated with cognitive performance. Within the intermediate-amyloid group, however, verbal episodic memory performance correlated positively with composite(b: 0.68) andright (b: 0.80)andleft (b: 0.68)angular gyrus [18 F]FDG uptake (all p<0.05).