Neuromag triux 306 channel meg system

MEG data were recorded with an Elekta Neuromag TRIUX 306-channel MEG system, with 102 magnetometers and 102 pairs of orthogonal planar gradiometers, inside a two-layer magnetically shielded room (model Ak3B, Vacuumschmelze GmbH), with internal active shielding active to suppress electromagnetic artefacts. Data were recorded at 1000 Hz with an online 0.1 Hz high-pass filter and 330 Hz low-pass filter. The subjects’ positions and movements inside the MEG scanner were measured during recordings with head-position indicator coils attached to subjects’ heads. The location of the coils—and additional points giving a representation of the subjects’ head shape—was digitalized with a Polhemus Fastrak motion tracker before the measurements. The head shapes were later used to co-register MEG data and structural MRI. Horizontal and vertical electrooculogram and electrocardiogram were recorded simultaneously with the MEG.

The MEG data was recorded in a magnetically shielded room with an Elekta Neuromag™ TRIUX 306 channel MEG system (Elekta Oy, Helsinki, Finland) with 102 sensor elements comprised of 102 orthogonal pairs of two planar gradiometer sensors and 102 axial magnetometer sensors. The data were recorded at a sample rate of 1 kHz with 32 bits. Immediately before each recording was started, trapped flux in any of the sensors were released by heating and re-cooling the sensor until all sensor channels had a noise value of maximum 5 fT/ $\sqrt{Hz}$ for magnetometers and 5 fT/(cm $\sqrt{Hz}$ ) for gradiometers.
Sound stimuli and trigger signals were provided with E-Prime 2.0 stimulation software (Psychology Software Tools, Sharpsburg, Pennsylvania, U.S.A.). After MEG data acquisition, the participants were tested with the MET for rhythm perception in a nearby silent room. Finally, anatomical MRI data was acquired using a 3T Trio system (Siemens, Erlangen, Germany) with a 3D T1-weighted (T1w) MPRAGE sequence (sagittal plane orientation, voxel size = 1 × 1 × 1 mm, number of slices = 176, ascending slice order, ascending view order, TR = 2,420 ms, TE = 3.7 ms, flip angle = 9 degrees, TI = 960 ms, FOV = 256 mm, matrix = 256 × 256, slice thickness = 1 mm, 32 channel head coil).