MRI acquisition
MRI data were acquired at MGH Martinos Center for Biomedical Imaging using a 32-channel radiofrequency head coil in a 3T Siemens scanner (Siemens 3T Skyra). Structural brain images were acquired using a T1-weighted three-dimensional multiecho magnetization-prepared rapid gradient-echo sequence (voxel size: 1 × 1 × 1 mm3, repetition time: 2500 ms, echo time: 1.69 ms, slice thickness 1 mm, flip angle: 7 °, and 176 slices; measurement time: ~6 min).On day 1 and day 3, four resting-state fMRI (rs-fMRI) sequences were acquired: (i) one before the tDCS application; (ii) two during the application of the tDCS; (iii) one shortly after the tDCS application. A whole-brain gradient-echo-planar-imaging sequence was used for functional scanning (voxel size: 3 × 3 × 3 mmTo apply the tDCS during the fMRI scans, we used the Neuroelectrics Multi-Channel MRI Extension Kit, which allows us to connect the device (outside the MRI room) to the participants in the MRI scanner, safely obtaining high-quality scanning during stimulation.