Aging of the Brain
aging the brain undergoes a number of changes. Cell numbers decrease
continuously and the amount of dendritic branching of cortical neurons
decreases. The number of amyloid plaques increases. Despite
these changes, there is remarkably little effect on cognitive function.
Alzheimer's disease is not a direct consequence of the normal effects of
aging. Rather, the disease should be seen as an abnormal consequence
of these changes. For example, amyloid plaques are commonly found
in the brains of aged individuals. However, it may be the reaction
to the presence of amyloid (ie., the generation of neuritic plaques, in
which dystrophic neurites and gliosis are seen to occur around the amyloid
deposit) which starts the pathogenic cascade.