Accumulation of Intraneuronal Amyloid-β is Common in Normal Brain

Intraneuronal amyloid-β (iAβ) accumulation has been demonstrated in Alzheimer disease (AD). Although extracellular amyloid plaques composed primarily of aggregated amyloid-β are one of the main pathological features of AD, functional characterization of iAβ is still lacking. In this study, we identified the normal distribution of iAβ through an analysis of hippocampal sections from a series of over 90 subjects with diverse antemortem clinical findings. In addition to AD cases, iAβ in pyramidal neurons was readily and reproducibly demonstrated in the majority of control cases. Similar findings for controls were made across all ages, spanning from infants to the elderly. There was no correlation of iAβ between gender, postmortem interval, or age. While the possible pathophysiological significance of iAβ accumulation in AD remains to be elucidated, careful examination of iAβ found in the normal brain may be informative for determining the biological role of iAβ and how this function changes during disease. Current findings support a physiological role for iAβ in neuronal function over the entire lifespan.