Dementia Information What happens to the brain in Alzheimer's disease? Our brains are responsible for everything we do, think or feel and it keeps all this functioning by passing messages to different areas of our brain responsible for different things. The message is sent along networks of brain cells via chemical messengers. If these networks are disrupted, the messengers can't get through to deliver their instructions and the brain gradually stops working properly. In Alzheimer's disease problems are thought to be caused by protein deposits called plaques and tangles that slowly develop over time. Plaques appear as disc-like collections of debris around a central core of a protein called amyloid and tangles are bundles of abnormal fibre-like material (called tau) that look like balls of string. As more and more of these plaques and tangles develop they cause brain cells to die and the brain to become smaller than normal.