MEG/EEG was recorded using a 306-channel Elekta Neuromag TRIUX (MEGIN Oy, Helsinki, Finland) whole-head MEG system (sampling rate 1 kHz and pass-band 0.03–330 Hz) in a magnetically shielded room (Euroshield/ETS Lindgren Oy, Eura, Finland) in BioMag Laboratory in Helsinki University Central Hospital (duration 2–3 h). Prior to the measurement, the positions of five head position indicator (HPI) coils and additional head surface points (EEG electrodes) were determined in relation to the nasion and both preauricular points with an Isotrak 3D-digitizer (Polhemus Inc., Colchester, USA). The head position with respect to the MEG sensor array was continuously monitored. Vertical and horizontal electro-oculograms (EOG) were recorded.
The anatomical T1-weighted images (MPRAGE) were acquired on a 3T MAGNETOM Skyra whole-body MRI scanner (Siemens Healthcare, Erlangen, Germany) with a 32-channel head coil at AMI centre of Aalto Neuroimaging (duration 30 min), Aalto University (176 slices, slice thickness 1 mm, voxel size 1 mm × 1 mm × 1 mm, field of view 256 mm × 256 mm). The images were checked for incidental findings by a physician.
The anatomical T1-weighted images (MPRAGE) were acquired on a 3T MAGNETOM Skyra whole-body MRI scanner (Siemens Healthcare, Erlangen, Germany) with a 32-channel head coil at AMI centre of Aalto Neuroimaging (duration 30 min), Aalto University (176 slices, slice thickness 1 mm, voxel size 1 mm × 1 mm × 1 mm, field of view 256 mm × 256 mm). The images were checked for incidental findings by a physician.