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DOI: 10.1177/0891988706291079 Alzheimers Disease and the Aging BrainDepartment of Neurosciences, University of California, San Diego, rterry{at}ucsd.edu The frequencies of each of the several types of dementia are enumerated, showing that Alzheimers disease is present in about 80% of cases. Cerebral changes associated with cognitively normal aging include shrinkage of large cortical neurons but not a significant loss of total neuronal number. Nevertheless, the population density of synapses measured by confocal microscopy does decline significantly in normal aging. The classical lesions of Alzheimers disease are neuritic plaques and neurofibrillary tangles, and their frequency correlates with declining cognitive measures. Although amyloid is prominent in plaques, it is probably not the agent of destruction. That role seems to be held by Aß oligomers. The strongest structural correlate with cognitive tests is synapse loss, which is probably caused by Aß oligopeptides in the terminal axons and dendrites. (J Geriatr Psychiatry Neurol 2006;19:125-128)
Key Words: Alzheimers disease neuritic plaques neurofibrillary tangles autopsy amyloid peptide
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