More specifically, since we performed a [123I]β-CIT scan at baseline, we cannot exclude the possibility that a change in SERT-to-DAT ratio occurs later in the course of the disease as a result of a slower progression of the degeneration of the serotonergic system compared to that of the dopaminergic system, particularly in patients that go on to develop dyskinesias. The gene discussed is SLC6A4; the disease is drug-induced dyskinesia.