Figure 4. Colocalization of levodopa-mediated cerebral blood flow (CBF) responses and dopaminergic deafferentation in the putamen and sensorimotor cortex of subjects with advanced Parkinson’s disease (PD).

(A) Left: [¹⁸F]fluorodopa (FDOPA) uptake was significantly reduced in the putamen (top) in both the 59 mild (light gray) and 47 advanced (dark gray) PD subjects, and in the sensorimotor cortex (SMC) (bottom) in the advanced patients, compared with 10 healthy control (NL) subjects. Right: In advanced PD subjects, cerebral metabolic rate (CMR) values were significantly higher than normal in the putamen (P < 0.001; Student’s t test) but only marginally increased in the SMC (P = 0.08), compared with 19 NL subjects. Arrows indicate Student’s t tests between the 2 PD groups. ^¶P < 0.10, ***P < 0.001, Student’s t test compared to NL values. Note the outlier with extremely low FDOPA uptake in the SMC (left, bottom); excluding this subject did not alter the significance of the group comparisons. (B) Regions with significant reduction in dopaminergic input (identified in a voxel-wise analysis of FDOPA PET scans from 47 advanced PD subjects) are denoted in red. Similarly, regions with significant CMR elevation (identified by voxel-wise analysis of [¹⁸F]fluorodeoxyglucose PET scans acquired in the same individuals) are denoted in green (see text). Areas of overlap (yellow) exhibit both dopaminergic deafferentation and increased local metabolic activity. In the current study, areas of dissociation (black contours) in the putamen (top) and areas of increased baseline CBF in the SMC (bottom) colocalized almost exclusively with areas of overlap (yellow) (insets). Maps of reduced FDOPA uptake were thresholded at T = 6.0, P < 0.001, uncorrected, for the putamen (top) and at T = 1.67, P < 0.05, uncorrected, for the SMC (bottom). Maps of increased CMR were thresholded at T = 1.67, P < 0.05, uncorrected, for both regions. Displays were superimposed on a standard MRI template.