The human body is a tireless gardener, growing new cells throughout life in many organs--in the skin, blood, bones and intestines. Until the 1980s most scientists thought that brain cells were the exception: the neurons you are born with are the neurons you have for life. In the past three decades, however, researchers have discovered hints that the human brain produces new neurons after birth in two places: the hippocampus --a region important for memory--and the walls of fluid-filled cavities called ventricles, from which stem cells migrate to the olfactory bulb, a knob of brain tissue behind the eyes that processes smell. Studies have clearly demonstrated that such migration happens in mice long after birth and that human infants generate new neurons. But the evidence that similar neurogenesis persists in the adult human brain is mixed and highly contested. [More]




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