Modified tau is present in younger nondemented persons: a study of subcortical nuclei in Alzheimer's disease and progressive supranuclear palsy.

Tau-positive neurons relating to neurofibrillary tangles and diffuse cytoplasmic stainings were quantitatively examined in the brains of 61 nondemented persons including 24 age-matched controls, 10 patients with Alzheimer's disease (AD) and 5 with progressive supranuclear palsy (PSP). In nondemented persons, the locus ceruleus (LC) was found to contain tau-positive neurons initially in persons in their 30s, whereas the hippocampus contained such neurons initially in persons in their 40s. The LC had a higher incidence and density than the hippocampus in almost all age classes. As neuronal tau accumulation is considered a histological change occurring with normal aging, the LC might be involved in the earliest aging in the normal brain. In AD there was conspicuous tau accumulation in the same sites which were vulnerable to tau accumulation in the age-matched controls. In PSP tau accumulated heavily in a set of sites different from the age-matched controls and AD. Thus, subcortical tau accumulation in AD is increased far more than that under normal aging process, while that in PSP is not simply in an increased state of the normal aging process.