Brain imaging plays an increasingly important role in experimental medicine for dementia by providing biomarkers for diagnosis, prognosis, patient stratification and monitoring treatment response. Imaging can also provide insights into mechanisms of risk and resilience for neurodegeneration. The Translational Neuroimaging Group investigate brain ageing in both health and disease. We have demonstrated that people at increased risk of later developing Alzheimer’s and Parkinson’s disease have particular ‘signatures’ of brain activity. I will introduce some of the methodology and describe how the techniques are being used to improve our understanding of brain ageing.