A new gene therapy targeting the small brain region where dopamine neurons reside, the substantia nigra, substantially boosts the benefits of the drug levodopa in Parkinson's. The therapy restored the ability of these neurons to convert levodopa to dopamine. Scientists also showed how damage to the powerplants inside dopamine-releasing neurons triggers Parkinson's. The findings may help identify humans in the earliest stages of Parkinson's disease, develop therapies to slow disease progression and treat late-stage disease.