Can the adult human brain grow new neurons and, if it could, would these new

neurons repair or even enhance its powers? These questions fascinate most

people because they concern human beings and the most distinctive organ

in humans, the brain. Unfortunately, they can be answered in multiple ways

depending on what is meant by “adult,” “brain” and “neurogenesis.” Over the

past two decades, whether and where the brain can show new growth has been a

source of controversy among brain researchers who have disagreed over the

evidence for claims of neurogenesis and over their implications and medical

applications. But in the popular media, expanded in online niches, the potential

for growing new brain cells is asserted enthusiastically, with chatty advice on

how to stimulate mental renewal and bright promises of cures for devastating

brain diseases.