MEG data were acquired using a 306-channel Neuromag MEG scanner (Vectorview, Elekta, Finland) made up of 102 triplets of two orthogonal planar gradiometers and one magnetometer. All recordings were performed inside a magnetically shielded room at a sampling rate of 1,000 Hz. Five head position indicator (HPI) coils were applied for continuous head position tracking, and visualized post-acquisition using an in-house Matlab script. For MEG-MRI coregistration purposes three fiducial points, the locations of the HPI coils and 300–500 points from the head surface were acquired using the integrated Polhemus Fastrak digitizer.
