These questions have plagued scientists for a long time, but time is something that the aging brain has little of. First of all, the cells in the brain are different from cells in other parts of our body. Unlike skin cells or muscle cells, which multiply in days or weeks, brain cells never divide after birth. However, what all of the cells in your body have in common is a limited life span (except for cancer cells). Generally, this life span is determined by the number of times a cell divides before it dies. While anti-aging theories of resetting our genetic time clocks may increase the number of times a cell divides and therefore prolong the life of a cell, this method would not solve the problem of brain cell death. Once brain cells are lost, they cannot be replaced. Thus, when the cells of the most vital organ in our body die, it affects us significantly.
