Credit: CENTRE JEAN PERRIN, ISM / SCIENCE PHOTO LIBRARY

Caption: Series of coloured sagittal positron emission tomography (PET) scans through the brain of a 78 year old man with frontotemporal dementia. These images show a diffuse atrophy (shrinkage) of the cortical and subcortical areas at the front of the brain. The colour-coded scans show metabolic activity from low (blue) to high (red, pink and white). PET scanning utilises an injected radioactive tracer to reveal variations in metabolic activity in the brain. Frontotemporal dementia is a rare form of dementia that causes behavioural changes and language difficulties.