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These diagrams represent PET scans that contrast DA levels in a Parkinson patient’s brain before, and 28 months after, implantation.
Research from “Bilateral Fetal Mesencephalic Grafting in Two Patients with Parkinsonism Induced by 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyradine (MPTP),” by H. Widner, J. Tetrud, S. Rehngrona, B. Snow, P. Brundin, B. Gustavii, A. Bjorklund, O. Lindvall, and J. W. Langston, 1992, New England Journal of Medicine, 327, p. 151.