Different rates of neuronal degeneration: an exquisite variation of the 'Cascade' hypothesis.

This morphometric, quantitative and correlative multivariate study of the hippocampal formation in human brains from two distinct normal aging populations provides an additional support to the notion that neuritic plaques (NP) are an earlier stage of the pathological process underlying neurofibrillary tangle (NFT) formation. It is shown that the rate of transformation of NP-affected neurons into NFT-bearing neurons may vary remarkably between distinct populations. In addition, it is put forward that different rates of neuronal degeneration may be one of the explanations for the existence of conflicting hypotheses regarding pathogenesis of NP and NFT and the relationships of these important histological markers to psychical deterioration.