Getting older usually means becoming increasingly forgetful, but for some of us it will mean much more than simple absent-mindedness. For millions of older people worldwide, advancing age can also mean the beginning of a steady decline in mental faculties that is characteristic of the devastating neurodegenerative deterioration in Alzheimer's disease. This form of senile dementia is a burden not only for the patient, because of the debilitation that the condition causes, but also for the families of sufferers, who must dedicate increasing time and resources to caring for their affected loved ones. The cost to society is also staggering, currently about £23 billion in Britain annually, and projected to rise to £50 billion by 2038 1 . Thus understanding what causes the neurodegeneration and how to treat it is a major priority for biomedical researchers. This research is dominated by the use of animals to study changes in the brain during development of the disease.