Stem cells that are naturally present in the brains of finches were induced to replace lost cells and restore the birds’ ability to sing their distinctive song. “Our results represent the restoration of a brain circuit involved in a complex learned behavior,” says Jeffrey Macklis, associate professor of neurology in the Division of Neuroscience at Harvard Medical School. “It is a step toward doing the same thing in mammals.” Mammals include humans, and Macklis sees the future possibility of using such approaches to treat damage done by spinal cord injuries, strokes, and degenerative conditions such as Huntington’s and Alzheimer’s diseases. Even keeping normal brain cells healthy, and thus slowing aging, is not out of the question.