Figure 1.

A-B: Schematic of task apparatus and the choice RT reaching task. C: Histologic immunolabeling for tyrosine hydroxylase (TH) revealed the depletion of dopaminergic innervation from the right striatum of both animal G (top) and I (bottom). D: Immunolabeling for TH (brown) and Nissl staining (magenta) demonstrate a marked reduction in TH labeling in the right lateral SNc of both animal G (top left) and I (bottom left). Note that TH labeling in the more medial right ventral tegmental area (VTA) was relatively preserved following the ICA MPTP administration. Inset panels (right) provide higher-magnification views of matching regions of the left and right lateral SNc (red dashed rectangles) and evidence the depletion of TH-label from the right lateral SNc. E: Densities of TH-positive somata in the SN (black bars) and VTA (gray bars), shown ad a percentage relative to the corresponding regions in the healthy control monkey L. Both animal G (top) and I (bottom) showed a selective depletion of TH-positive neurons in the right SN, while the left SN and both VTAs remained relatively preserved.

F-H: Behavioral measures of task performance for both animals before and after MPTP administration (green and magenta, respectively). Both animals performed the task in a highly stereotyped fashion with short RTs (F), MDs (G), and return durations (H) prior to MPTP administration. RT and MD were slowed significantly following MPTP. H: Following MPTP, both animals displayed an extremely prolongation of the time required to return the hand to the start position. The experimenter intervened and assisted return movements if they were not initiated by the animal within 4 sec. of reward delivery, thus resulting in return durations of >6 sec (green shading). Means +/− SEM. Statistical differences were computed using a 3-way ANOVA followed by Tukey’s test; (**: main effect of MPTP, p<0.01; ††: MPTP × target interaction, p<0.01).