Light micrograph of senile (neuritic) plaques showing amyloid core. Alzheimer's disease causes a decrease in brain volume, due to the degeneration and death of nerve cells, and the surface of the brain is often more deeply folded. Tangled protein filaments (neurofibrillary tangles) occur within nerve cells and patients also develop brain lesions of beta- amyloid protein. Alzheimer's disease accounts for most cases of senile dementia. Symptoms include memory loss disorientation, personality change and delusion. It ultimately leads to death. Magnification: 250x.