Can we, as adults, grow new nerve cells? There's still some confusion about that question, as this is a fairly new field of research. For example, I was talking to one of my colleagues, Robert, who is an oncologist, and he was telling me, "Sandrine, this is puzzling. Some of my patients that have been told they are cured of their cancer still develop symptoms of depression." And I responded to him, "Well, from my point of view that makes sense. The drug you give to your patients that stops the cancer cells multiplying also stops the newborn neurons being generated in their brain." And then Robert looked at me like I was crazy and said, "But Sandrine, these are adult patients -- adults do not grow new nerve cells." And much to his surprise, I said, "Well actually, we do." And this is a phenomenon that we call neurogenesis.