"It would be ironic if the shortfall in a same gene brokered the path to brain disease or rejuvenation," says Nottebohm, who is Dorothea Leonhardt Professor and head of the Laboratory of Animal Behavior. "But naturally replaced neurons may hold the key to understanding processes of neurodegeneration."
The results appear in the May 23 Early Edition issue of Proceedings of the National Academy of Sciences.
The potential medical implications of the study came as a surprise to the researchers. They set out to answer fundamental questions about the small number of brain neurons that can be replaced when they die: Are these cells similar to other neurons that are not replaced in adult life? Or, in terms of which genes are "turned on," are they marked as transient?
Nottebohm's laboratory has pioneered the study of the brain pathways controlling how songbirds learn to sing. A discrete region of the brains of songbirds, known as the high vocal center, controls their singing behavior. It was in this brain region that, more than 20 years ago, Nottebohm discovered new neurons being born in adult birds, overturning the conventional wisdom that all neurons in vertebrates are created by birth or soon after.
In the new study, the researchers looked at cells in the high vocal center region of the brains of 19 zebra finches, a kind of songbird native to Australia that has long been used in studies of birdsong. Since replaceable neurons sit side-by-side with neurons that are not replaced, the first step was to label the two kinds of cells in order to tell them apart.