I've long said that repairing and sustaining the brain is a vital goal for longevity, and that we will see overcoming myriad neurodegenerations as the greatest challenge to healthy life extension two or three decades from now. Progress is being made, however, as reported by ScienceAlert : "neuroscientists have identified the stem cell population responsible for production of neurons, and the mechanism which drives this process. ... For the first time, we've been able to identify a mechanism that's able to regulate production of nerve cells, a step that's crucial to our understanding of memory and learning. The same mechanism helps regulate growth of healthy brain tissue, so identifying this process is essential for the development of therapeutics to treat conditions such as dementia. ... With this knowledge, we are well placed to further develop our understanding of the basic mechanisms that regulate the generation of healthy, new nerve cells in the brain. Our long-term goal is to develop new therapies whereby nerve cells can be generated to replace those lost or damaged in disease or trauma."