CEREBRAL-CORTEX PATHOLOGY IN AGING AND ALZHEIMERS-DISEASE - A QUANTITATIVE SURVEY OF LARGE HOSPITAL-BASED GERIATRIC AND PSYCHIATRIC COHORTS

In order to explore the relationships between the involvement of speci fic neuronal populations and cognitive deterioration, and to compare t he hierarchical patterns of cortical involvement in normal brain aging and Alzheimer's disease, over 1200 brains from elderly subjects witho ut cognitive deficits, as well as from patients with age-associated me mory impairment and Alzheimer's disease, were examined. Our results su ggest that the neuropathological changes associated with normal brain aging and Alzheimer's disease affect select cortical circuits at diffe rent points in time. Extensive hippocampal alterations are correlated with age-associated memory impairment, whereas substantial neurofibril lary tangle formation in neocortical association areas of the temporal lobe is a prerequisite for the development of Alzheimer's disease. De spite several lines of evidence involving amyloid deposit in the patho genesis of Alzheimer's disease and Down's syndrome, our observations i ndicate that there is no correlation between senile plaque densities a nd degree of dementia in both disorders. In contrast to younger elderl y cases, in the ninth and tenth decades of life, there is a differenti al cortical involvement in that parietal and cingulate areas are early affected in the course of Alzheimer's disease, and neocortical senile plaques densities are strongly correlated with the severity of dement ia. Moreover, Alzheimer's disease symptomatology is characterized in t hese very old patients by high neurofibrillary tangle densities in the anterior CA1 field, but not in the entorhinal cortex and inferior tem poral cortex. These observations are discussed in the light of the hyp othesis of global corticocortical disconnection and with respect to th e notion of selective neuronal vulnerability in Alzheimer's disease. ( C) 1997 Elsevier Science B.V.