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Hippocampal atrophy, amyloid plaques, and neurofibrillary tangles are established pathologic markers of Alzheimer's disease. We analyzed the temporal lobes of 9 Alzheimer's dementia (AD) and 7 cognitively normal (NC) subjects. Brains were scanned post-mortem at 7 Tesla. We extracted hippocampal volumes and radial distances using automated segmentation techniques. Hippocampal slices were stained for amyloid beta (Aβ), tau, and cresyl violet to evaluate neuronal counts. The hippocampal subfields, CA1, CA2, CA3, CA4, and subiculum were manually traced so that the neuronal counts, Aβ, and tau burden could be obtained for each region. We used linear regression to detect associations between hippocampal atrophy in 3D, clinical diagnosis and total as well as subfield pathology burden measures. As expected, we found significant correlations between hippocampal radial distance and mean neuronal count, as well as diagnosis. There were subfield specific associations between hippocampal radial distance and tau in CA2, and cresyl violet neuronal counts in CA1 and subiculum. These results provide further validation for the European Alzheimer's Disease Consortium Alzheimer's Disease Neuroimaging Initiative Center Harmonized Hippocampal Segmentation Protocol (HarP).

Cell counts in the cholinergic nucleus basalis (NB), noradrenergic locus coeruleus (LC), dopaminergic substantia nigra (SN), and the serotonergic dorsal raphe nucleus (DRN) were assessed from primary-level reports in patients with Alzheimer disease (AD) and in controls. Sixty-seven studies that covered about 20 years were included in the meta-analysis. Effect sizes were computed as a standardized mean difference (d) in cell counts between AD and controls. Effect sizes were largest in magnitude for the NB (mean d=2.48, 33 studies, N=585), and the LC (d=2.28, 24 studies, N=545), then the DRN (d=1.79, 11 studies, N=234), and were smallest for the SN (d=0.61, 14 studies, N=440). In general, the overall effect size estimates for the four cell areas were reliable. Using effect size magnitude in the SN as a referent, cell loss was about three times greater in the DRN and four times greater in the NB and LC. Symptomatic drug treatment for AD might be beneficially directed toward ameliorating multiple neurotransmitter deficiencies, particularly cholinergic and noradrenergic.

Numbers of neurons in the nucleus basalis of Meynert were estimated in seventeen non-demented patients who died of chronic hepatic or cardiopulmonary disease. Neurons were counted at the site of maximal neuronal density (SMND). This site was chosen by reviewing serial sections around the decussation of the anterior commissure and appeared to be comparable in different individuals. No correlation between numbers of neurons and age could be found. It appears that no uniform neuronal loss occurs in the nucleus basalis with age. Taken together with biochemical studies of cerebral cortical choline acetyltransferase activity, these findings suggest that there is no overall change in cholinergic input to cerebral cortex with age.