Preprocessing and analysis of fMRI data
REGRESSION
fMRI data were processed using SPM12 (v7771, We controlled fMRI data quality by monitoring the scan-to-scan total displacement (mean total displacement <1.5 mm) [First, we replicated the manipulation-related regional activation. The general linear model convolved a design matrix with a canonical hemodynamic response function at the subject level. The design matrix included correct and incorrect ordered and random trials as separate regressors. Each trial was time-locked to its onset. The total displacement was included as a nuisance regressor. Classical parameter estimation was applied with a one-lag autoregressive model. The manipulation-related activation was defined as correct random Second, we detected pramipexole effects on regional activity in fronto-subthalamic and fronto-striatal pathways. The left dlPFC and left striatal regions were derived from a meta-analysis of 1091 fMRI studies on working memory (NeuroSynth) [Third, we explored relationships between behavior and fronto-subthalamic and fronto-striatal pathways. We examined whether the pramipexole-induced RT change (ordered trials) correlated with the maintenance-related regional activity change in the dlPFC, STN, or striatum (stepwise regression in the IBM SPSS, Fourth, we detected pramipexole effects on prefrontal activity pattern similarity. Beta values of ordered and random trials (i.e., model-based estimates of fMRI signals without time dimension) were extracted from dlPFC voxels and sorted spatially according to MNI coordinates. Pearson correlation coefficients were computed between the betas of ordered trials and those of random trials, normalized using Fisher’s transformation, and entered into a paired Finally, we detected pramipexole effects on fronto-subthalamic functional connectivity. Raw fMRI signals were extracted from the left dlPFC and left STN regions and demeaned. Pearson correlation coefficients were computed between the dlPFC and STN signals, normalized using Fisher’s transformation, and entered into a paired 