Degenerative adversarial neuroimage nets for brain scan simulations: Application in ageing and dementia

•We implemented a new deep learning framework capable of synthesising realistic and accurate 4D brain MRI in ageing and Alzheimer’s disease.•We proposed a sequence of memory-efficient techniques designed to improve model stability, reduce artefacts, and improve individualization.•Synthesised T1w MRI scans contain only minor structural differences with real data, and have minimal noise/texture artefacts.•Synthesised MRI scans were diagnostically indistinguishable from real scans.•Synthetic MRI can be used for: i) data augmentation, ii) model validation and iii) understanding biological/disease mechanisms in the brain.