Alzheimer's disease. Light micrograph of a section through the brain of a patient suffering from Alzheimer's disease. Senile plaques (large red circles, for example at centre) are a feature of Alzheimer's. The nerve cells (neurones) in the brains of sufferers degenerate and die, causing a deterioration in brain function. The plaques form when material from dying nerve cells accumulates around protein. Neurofibrillary tangles, twisted fragments of protein within the neurones, also form. These prevent the neurones from processing sensory information. This is the outer layer (cortex) of the occipital lobe at the base of the brain. Magnification unknown.