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Approximately 30% of healthy persons aged over 75 years show A[beta] deposition at autopsy. It is postulated that this represents preclinical Alzheimer's disease (AD). We evaluated the relationship between A[beta] burden as assessed by PiB PET and cognitive decline in a well-characterized, non-demented, elderly cohort. PiB PET studies and cognitive tests were performed on 34 elderly participants (age 73 [plus or minus] 6) from the longitudinal Melbourne Healthy Aging Study (MHAS). Subjects were classified as being cognitively "stable" or "declining" by an independent behavioural neurologist based on clinical assessment and serial word-list recall scores from the preceding 6-10 years. Decline was calculated from the slope of the word-list recall scores. A[beta] burden was quantified using Standardized Uptake Value normalized to cerebellar cortex. Ten subjects were clinically classified as declining. At the time of the PET scans, three of the declining subjects had mild cognitive impairment, one had AD, and six were declining but remained within the normal range for age on cognitive tests. Declining subjects were much more likely to show cortical PiB binding than stable subjects (70% vs. 17%, respectively). Neocortical A[beta] burden correlated with word-list recall slopes (r = -0.78) and memory function (r = -0.85) in the declining group. No correlations were observed in the stable group. A[beta] burden correlated with incident memory impairment and the rate of memory decline in the non-demented ageing population. These observations suggest that neither memory decline nor A[beta] deposition are part of normal ageing and likely represent preclinical AD. Further longitudinal observations are required to confirm this hypothesis. (Contains 4 tables and 4 figures.)

The ε4 polymorphism of the APOE gene confers a substantially increased risk of developing Alzheimer's disease. However, the influence of the ε4 allele on age-related cognitive functioning is more contentious. Previously, we demonstrated relatively little evidence for a role of the ε4 allele on baseline cognitive performance in older adults in the Australian Imaging, Biomarkers and Lifestyle (AIBL) Study of Ageing (Foster et al., 2013). We here investigated whether the APOE ε4 allele influenced cognitive status over time when the AIBL cohort was studied longitudinally over a 3-year period. The AIBL neuropsychological test battery was administered at baseline, after 18 months and again after 36 months. Participants comprised 764 Healthy Controls and 131 Mild Cognitively Impaired individuals enrolled in the AIBL Study of Ageing. We compared individuals within each group with and without an ε4 allele. Healthy Controls with an ε4 allele manifested a modest acceleration in cognitive decline over 36 months on measures of verbal episodic memory. By contrast, Mild Cognitively Impaired individuals with an ε4 allele showed increased cognitive decline across a range of cognitive tasks, putatively reflecting early cognitive signs of Alzheimer's disease. Given the long prodromal period that has been noted in late onset Alzheimer's disease, we suggest that these findings are consistent with a prodromal account rather than a phenotypic account of ε4-related cognitive ageing., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Scopolamine-induced deficits in cognitive and motor processes have been widely demonstrated in animals and humans, although the role of acetylcholine in working memory is not as well understood. This study examined the role of acetylcholine neurotransmission in visuospatial short term and working memory using the Groton Maze Learning Test (GMLT). The GMLT is a computerized hidden maze learning test that yields measures of component cognitive processes such as spatial memory, working memory, and visuomotor function, as well as their integration in trial-and-error problem solving. Healthy older adults were administered scopolamine (0.3 mg subcutaneous), the acetlycholinesterase inhibitor donepezil (5 mg oral), scopolamine with donepezil, or placebo. Compared to placebo, low-dose scopolamine led to performance deficits on all measures of the GMLT. The greatest scopolamine-induced deficits were observed in errors reflecting working memory processes (e.g., perseverative errors d=-2.98, and rule-break errors d=-2.49) and these impairments remained robust when statistical models accounted for scopolamine-related slowing in visuomotor speed. Co-administration of donepezil partially ameliorated scopolamine-related impairments and this effect was greatest for measures of working memory than short-term memory. By itself, donepezil was associated with a small improvement in visuomotor function. These results suggest that scopolamine disrupts processes required for rule maintenance and performance monitoring, in combination with visuomotor slowing and sequential location learning.