Aging is associated with declines in multiple components of the dopamine system including loss of dopamine-producing neurons, atrophy of the dopamine system’s cortical targets, and reductions in the density of dopamine receptors. Countering these patterns, dopamine synthesis appears to be stable or elevated in older age. We tested the hypothesis that elevation in dopamine synthesis in aging reflects a compensatory response to neuronal loss rather than a nonspecific monotonic shift in older age. We measured individual differences in striatal dopamine synthesis capacity in cognitively normal older adults using [18F]Fluoro-l-m-tyrosine positron emission tomography cross-sectionally and tested relationships with longitudinal reductions in cortical thickness and working memory decline beginning up to 13 years earlier. Consistent with a compensation account, older adults with the highest dopamine synthesis capacity were those with greatest atrophy in posterior parietal cortex. Elevated dopamine synthesis capacity was not associated with successful maintenance of working memory performance overall, but had a moderating effect such that higher levels of dopamine synthesis capacity reduced the impact of atrophy on cognitive decline. Together, these findings support a model by which upregulation of dopamine synthesis represents a mechanism of cognitive resilience in aging.

Little is known about the association between personality and Alzheimer's disease (AD) biomarkers, and existing results are inconsistent. We aimed to determine whether personality was associated with ␤-amyloid (A␤) accumulation in cognitively normal aging. One hundred twenty-nine participants were included in this cross-sectional study. Personality was measured with the Big Five Inventory (BFI) and brain A␤ deposition was assessed with [ 11 C] Pittsburgh compound B (PiB)-positron emission tomography (PET) imaging. Conscientiousness scores had a negative association with global PiB distribution volume ratio (DVR) in all participants after adjusting for age, sex, education, and vascular risk factors (␤[SE] ϭ Ϫ0.19[0.09], 95% confidence interval [CI: Ϫ0.35, Ϫ0.02], p ϭ .031), while agreeableness, extraversion, neuroticism, and openness had no association with global PiB DVR. Assuming the relative stability of personality traits, these findings suggest that conscientiousness may protect against A␤ accumulation in cognitively normal aging through mechanisms that are as yet unknown.

Difficulty retrieving proper names is common in older adults, coinciding with the accumulation of aggregated proteins in mid-life. We investigated the ability of healthy older adults to retrieve the names of famous faces in relation to positron emission tomography measurements of amyloid-β plaques and tau neurofibrillary tangles. More tau in the left fusiform and parahippocampal gyrus was related to reduced proper name retrieval performance and this effect was potentiated by amyloid-β. These findings provide an explanation for a common complaint of older adults and link proper name retrieval to neural systems involved in face perception, memory, and naming.

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