Figure 3. Increased resting activity in the sensorimotor cortex in unmedicated levodopa-induced dyskinesia (LID) and non-LID (NLID) subjects.

(A) Voxel-wise comparison of baseline (OFF) cerebral blood flow (CBF) scans from the 14 NLID and 14 LID subjects revealed significantly increased bilateral resting activity in the sensorimotor cortex (SMC) in the latter group. Clusters were displayed using a red–yellow scale thresholded at T = 3.47 (P < 0.001, uncorrected, with cluster extent >100 voxels), superimposed on a single-subject MRI template. (B) Box-and-whisker plots of the individual subject SMC data. During levodopa infusion (ON), regional CBF values (left) increased significantly in both NLID and LID subjects, whereas cerebral metabolic rate (CMR) values (right) were not altered by drug. Arrows indicate post hoc Bonferroni tests for group comparisons in the 2-way 2 × 2 repeated-measures ANOVA. Horizontal lines represent Student’s t tests comparing local values measured in the LID and NLID groups. *P < 0.05, Student’s t test compared with normal (NL; n = 14) values. (C) Receiver-operating characteristic curves showing the discrimination of LID from NLID subjects based upon the combination of putamen dissociation index (DI) and resting SMC CBF (blue curve) or CMR (red curve) values measured in the baseline unmedicated condition. Accurate discrimination of individual subjects was achieved by logistic regression models based on these variables (P < 0.002). Each of the 2-variable discriminant models was superior to a 1-variable model (dotted curve) in which symptom duration was the only predictor (P < 0.02).