While the mainstay of treatment for PD remains levodopa, which restores brain dopamine levels, its chronic use is fraught with several problems, including loss of drug efficacy, erratic (on-off) responses, and abnormal hyperkinetic movements such as levodopa-induced dyskinesia, a common motor complication related to dopamine transporter loss and abnormal connectivity in the putamen13,14. This evidence concerns the gene SLC6A3 and Parkinson disease.