Introducing three genes corrects motor defects in monkeys.A potential gene therapy for Parkinson's disease can correct motor deficits in monkeys without causing the jerky, involuntary movements that often accompany long-term treatments for the disease. The approach is undergoing preliminary testing in a handful of human patients, who have all shown promising signs of improvement.At present, the most common remedy for Parkinson's disease involves replacing dopamine — the neurotransmitter that is depleted in patients with the disease — by administering the dopamine precursor levodopa, or L-DOPA. Most patients initially regain near-normal motor control, but after several years on L-DOPA the majority...