The brains of individuals who are cognitively normal show age-related changes that include
an overall reduction in the brain volume and weight and enlargement of the brain ventricles.
These changes are partly the result of nerve cell loss but accurate estimates of neuronal loss
are notoriously difficult to make. There is loss of synapses and dendritic pruning in the aged
brain but in selected areas rather than globally. Neurofibrillary tangles and senile plaques
are the neuropathological hallmark of Alzheimer's disease in which they are more abundant …