Alzheimer's disease: maintenance of neuronal and synaptic densities in frontal cortical layers II and III.

Neuronal loss and alterations of the cortical neuropil were previously described on necropsic material from patients with senile dementia of the Alzheimer type, and the results compared to age-matched case controls. In frontal cortex biopsic material from our patients with Alzheimer's disease, the numerical densities of neurons and synapses were not significantly different from controls, indicating that changes in the highest cognitive functions might not depend on a generalized loss of neurons and synapses and that quantitative morphological differences may exist between Alzheimer's disease and senile dementia of the Alzheimer type.