After injury, adult neurons regrow their long, signal-conducting axons to form connections called synapses with other neurons. But the regrown cells cannot conduct electrical signals properly. Michela Fagiolini and Zhigang He of Children's Hospital Boston in Massachusetts and their team studied mice with injured optic nerves. Deleting two genes that regulate neuronal growth, or boosting the production of two protein-growth factors, regenerated retinal axons that formed synapses in the brain, but did not improve vision. Treating the neurons with a compound that improves their conductivity helped them to work properly. This restored vision in six of the eight experimental animals.