MEG data were recorded in a one-layer magnetically-shielded room with active shielding engaged to compensate for environmental noise. Neuromagnetic responses were sampled at 1 kHz using an Elekta MEG system (Helsinki, Finland) equipped with 102 magnetometers and 204 planar gradiometers. All analyses focused on the data from the 204 planar gradiometers. Participants were monitored during MEG acquisition by real-time audio–video feeds from inside the room. Each participant’s data was individually corrected for head movement using four position indicator coils attached to the participant’s head, which were continuously measured throughout recordings. The data were also subjected to noise reduction using the temporally-extended signal space separation method51,52.
