Syncbox device

MRI imaging and simultaneous EEG-fMRI was conducted using a General Electric Discovery MR750 whole-body 3 T MRI scanner with a standard 8-channel, receive-only head coil array. A single-shot gradient-recalled EPI sequence with Sensitivity Encoding (SENSE) was employed for the fMRI acquisition. EEG signals were recorded simultaneously with fMRI using a 32-channel MR-compatible EEG system (Brain Products GmbH) with measuring electrodes arranged according to the international 10–20 system. ECG signal was recorded using an electrode on the subject’s back. In order to synchronize the EEG system clock with the 10 MHz MRI scanner clock, a Brain Products’ SyncBox device was utilized. The EEG acquisition of temporal resolution and measurement resolutions was 0.2 ms (i.e., 16-bit 5 kS/s sampling) and 0.1 μV, respectively. A hardware filtering throughout the acquisition in a frequency band between 0.016 and 250 Hz was applied to EEG signals.
We included EEG data collected from 113 subjects during resting EEG-fMRI run lasting 8 min. The participants were instructed to relax and keep their eyes open and fixate their eyes on a cross displayed on the fMRI stimulus projection screen. For this work, we did not use and analyze fMRI data.

MRI was performed on a General Electric 3T MR750 scanner (GE Healthcare Systems, Chicago, IL) using the body coil for radiofrequency transmission and a 12‐channel head coil for signal reception. Resting‐state fMRI data were acquired using a gradient‐echo echo‐planar imaging sequence in a plane parallel to the AC‐PC line, 2160 msec repetition time (TR), 25 msec echo time, 75° flip angle, 36 interleaved slices of 64 × 64 matrix size, giving a 211 × 211 mm field of view with a voxel size of 3.3 × 3.3 × 3.3 mm. Simultaneous EEG was recorded during the fMRI scan at a sampling frequency of 5 kHz with the SyncBox device (Brain Products) used to synchronize EEG and fMRI acquisition. A three‐dimensional inversion recovery‐prepared spoiled gradient‐echo image was acquired in the sagittal plane with 270 mm field of view, 256 × 256 matrix (resulting in an in‐plane voxel size of 1.05 × 1.05 mm), 196 sagittal slices, 1.2 mm slice thickness, 7.312 msec TR, 400 msec inversion time, 3.016 msec echo time, and 11° excitation flip angle.