Brainamp exg mr system

The acquisition was performed on the Siemens Prisma 3 T MR whole-body scanner with 64-channel head-neck coil. A high-resolution structural T1 image was scanned for each participant. This makes it possible to localize the active brain areas more accurately than using functional images only. Parameters of the MPRAGE sequence were 240 sagittal slices, repetition time (TR) = 2300 ms, echo time (TE) = 2.34 ms, field of view (FOV) = 256 mm, flip angle = 8°, slice thickness = 1 mm). Functional blood-oxygen-level dependent (BOLD) MR data were acquired in a single scanning session with a T2*-weighted multiecho multiband echo-planar imaging (ME MB EPI) sequence of 1250 scans (60 slices, TR = 1000 ms, TE = 14, 34.63 and 55.26 ms, FOV = 200 mm, flip angle = 50°, slice thickness = 2.5 mm, MB factor = 5). TE values were chosen according to recommendations for ME EPI [55 (link)], where the second echo was very close to the typical value of single echo acquisition. Simultaneously with the fMRI data, ECG and respiration were measured by Brain Products BrainAmp ExG MR system with 5 kHz sampling frequency. Both signals were corrected for MR gradient artifacts [56 (link)] in Brain Vision Analyzer 2 and then used for RETROICOR correction of fMRI data. Processed ECG signal was also used for HRV calculation.

Brain activity was recorded with 248 magnetometers in blocks of 30 trials at a sampling rate of 1017.25 Hz using the Magnes 3600 WH MEG system from 4D-Neuroimaging (San Diego, United States of America). This resulted in a total of three ∼13-min MEG recording runs per participant. At the beginning and at the end of each recording run, the participant’s head position was determined. Cardiac and ocular activity were recorded at a sampling rate of 5,000 Hz using electrocardiography (ECG) and electrooculography (EOG) with the BrainAmp ExG MR system from Brain Products (Gilching, Germany). Eye movements were recorded at a sampling rate of 1,000 Hz using the EyeLink 1000 Long Range eye tracker from SR Research (Ottawa, Ontario, Canada).
At the beginning of each recording run and after every six trials, the eye tracker was calibrated using EyeLink’s 13-point calibration method (SR Research Ltd., 2009 ). If the average deviation was above 0.5° or the maximum deviation at one of the calibration points was higher than 2°, the calibration was repeated.
A structural MR scan was performed with a MAGNETOM Trio 3T MRI scanner from Siemens (Munich, Germany) using MPRAGE (Mugler and Brookeman, 1990 (link)). The MR scan was used for the localization of the sources in the brain that gave rise to the signal recorded at the MEG sensors.