2.2. Data Preprocessing

The resting-state fMRI data were obtained using the Data Processing Assistant for Resting-State fMRI (DPARSF) toolbox [22] and Statistical Parametric Mapping (SPM12) [23]. Briefly, data from the first 10 time points were removed, and slice timing correction was performed. Then, the images of all subjects were realigned for head movement, which did not exceed 2.0 mm of displacement or 2.0° of rotation in any direction. The image space was standardized to the Montreal Institute of Neurology (MNI) head anatomy template and resampled with 3 mm × 3 mm × 3 mm voxels. The linear trends of time series were removed, and the effect of nuisance covariates was removed by signal regression using the global signal, the motion parameters, the cerebrospinal fluid (CSF), and white matter (WM) signals. Subsequently, 0.01–0.027 Hz (slow5), 0.027–0.073 Hz (slow4), 0.073–0.198 Hz (slow3), 0.198–0.25 Hz (slow2), and 0.01–0.25 (full-frequency) bandpass filters were applied to the time series of each voxel [24]. Finally, a Gaussian filter with a full width at half maximum (FWHM) of 6 mm was used to smooth the image.