Rett syndrome is a rare neurodegenerative disorder that almost exclusively affects girls. It is typically diagnosed in babies between six and 18 months of age, when the first symptoms begin to appear.

In her time at Duke, Khanh Vien figures she's dissected close to 10,000 fly brains. For her Ph.D. she spent up to eight hours each day peering at baby flies under the microscope, teasing out tiny ...