Synchronization facilitates removal of MRI artefacts from concurrent EEG recordings and increases usable bandwidth

Investigating human brain function non-invasively by simultaneous EEG and fMRI measurements is gaining in popularity as more and better solutions to the inherent technical challenges emerge. We demonstrate the use of a commercially available frequency divider and phase-locking device for the purpose of synchronizing an MRI acquisition with a simultaneous recording of the EEG. Synchronization hugely improves the effectiveness of MRI artefact removal from the EEG signal by the common mean template subtraction method. It complements or substitutes post-processing techniques like filtering, thereby increasing the usable bandwidth of the EEG signal to about 150 Hz. This is important for covering the full range of human Gamma band activity. Similarly, synchronization eliminates the necessity for over-sampling of the EEG signal.