Whether or not we grow new brain cells as adults has been the subject of an ongoing and often contentious debate. Now, evidence suggests that we can. This could help answer one of neuroscience's most controversial questions and has sparked some speculation that the process could be exploited to treat conditions like depression and Alzheimer's disease. New neurons form via a process called neurogenesis in children, as well as in adult mice and macaques. This involves stem cells repeatedly giving rise to so-called progenitor cells that proliferate to form immature neurons that later become fully developed. Prior studies on human adults have identified stem cells and immature neurons in the hippocampus.

Will a regular exercise routine and a healthy diet keep your brain young? It depends on your genes. People who have certain forms of genes that play a key role in brain ageing seem to respond better to healthy lifestyle interventions. These make it "more likely that exercise or adhering to a Mediterranean diet will have a greater impact on your cognitive ageing," says Sandrine Thuret at King's College London. Cognitive ageing is thought to rely on neural stem cells in the brain's hippocampus which continue to produce new neurons throughout life, and are thought to play an important role in forming new memories.