Is senile dementia of the Alzheimer type (SDAT) the end result of aging of the brain (serial or aging-related model) or the result of some other mechanism that runs in parallel to normal aging (parallel or age-related model)? This question can be answered by comparing variables that measure biological aging (aging-dependent variables, ADVs) of normal individuals and of SDAT patients. If the serial model applies, the values of the ADVs of SDAT patients should be at the upper end of the normal ADV curves. In control individuals the power of the alpha band in the 2-Hz flash-stimulated EEG at the posterior head regions increased with age, while the power of the delta band in the resting EEG at the anterior head regions decreased. In SDAT patients the ADVs were significantly different from normal and opposite to the trend of normal aging, supporting the parallel model and suggesting that the pathogenesis of SDAT is different from normal aging.