306 channel meg

MEG was recorded from 12 healthy right-handed subjects (27.5 ± 4.5 years of age, mean ± standard deviation; 7 women) with a 306 channel MEG (Elekta Neuromag, Helsinki, Finland) at 600-Hz sampling rate as described earlier in (Hirvonen & Palva, 2016 (link)). Electromyogram (EMG) was recorded to detect the thumb movement responses and T1-weighted anatomical MRI scans were obtained for source localization. The study was approved by the Coordinating Ethical Committee of the Helsinki University Hospital, and the subjects gave a written, informed consent prior to their participation in the experiment.

We recorded 306-channel MEG (Elekta-Neuromag, Helsinki, Finland) and 74-channel EEG data simultaneously in a magnetically shielded room (sampling rate 1 kHz, passband 0.03–330 Hz). The average reference was utilized for all analyses of EEG data. The position of the head relative to the MEG sensor array was monitored continuously using four head position indicator (HPI) coils attached to the scalp. Electrooculogram (EOG) was also recorded to monitor eye artifacts. T1-weighted structural MRIs were obtained for combining anatomical and functional data using a multi-echo MPRAGE pulse sequence (TR = 2510 ms; 4 echoes with TEs = 1.64 ms, 3.5 ms, 5.36 ms, 7.22 ms; 176 sagittal slices with 1×1×1 mm³ voxels, 256×256 mm² matrix; flip angle = 7°). Multi-echo FLASH data were obtained with 5° and 30° flip angles (TR = 20 ms, TE = 1.89+2n ms [n = 0–7], 256×256 mm² matrix, 1.33-mm slice thickness) for reconstruction of head boundary-element models (BEM).