Imaging Data Acquisition and Preprocessing

MRI data were acquired on a 3-Tesla scanner (Magnetom Verio; Siemens Medical Solutions, Erlangen, Germany). Functional images were collected using an echo planar sequence (echo time = 30 ms; repetition time = 2,000 ms; flip angle = 90°; slice thickness = 3 mm; field of view = 240 mm; and matrix = 64 × 64). T1-weighted images were also collected using a 3D spoiled-gradient-recall sequence (echo time = 2.46 ms; repetition time = 1,900 ms; flip angle = 9°; slice thickness = 1 mm; number of slices = 176; and matrix size = 256 × 256).

Using the Statistical Parametric Mapping (SPM)12 (Wellcome Department of Cognitive Neurology, Institute of Neurology, London, United Kingdom¹) and MATLAB 2018a (Mathworks, Natick, MA, United States), the following image-preprocessing steps were conducted in order: realignment on the first image, slice-timing correction, co-registration and spatial normalization using a standard Montreal Neurological Institute (MNI) template, and smoothing using a Gaussian kernel with a full-width at half maximum of 8 mm.