Light micrograph of human brain tissue in Alzheimer's disease, showing a senile plaque (circular lesion at left), a characteristic histological feature of the disease. Alzheimer's disease is a form of progressive dementia; the brain is smaller than normal, with degenerative changes affecting the frontal and temporal lobes. Senile plaques are tangled masses of filaments & granules, often centred around an area of dark- staining amyloid protein. The main other feature of Alzheimer's disease is the formation of neurofibrillary tangles, masses of thickened filaments in the cytoplasm of neurons (nerve cells). Magnification: x130 at 35mm size.