Cardiac Cycle Artefact Removal in Magnetoencephalographic Data of Patients with Deep Brain Electrodes - Implementation of Simultaneous Magnetoencephalographic and Local Field Potential Recordings

Simultaneous magnetoencephalography (MEG) and local field potential (LFP) recordings in patients undergoing deep brain stimulation (DBS) for severe movement disorders is a promising technique both for clinical applications and basic research. Recordings can be accomplished during the time interval between electrode insertion and implantation of the stimulator while electrodes are externalised. At present, strong cardiac cycle artefacts (CCA) are observed in the MEG signals around the area, where the disposable stainless steel electrode wires leave the skull. The CCA refers to the remanent magnetic field of those wires underneath the sensors, which are moved by local pulsations of the blood vessels. Here, we demonstrate a new approach to partially remove the CCA by applying principal component analysis (PCA) to an averaged CCA and subsequent signal space projection (SSP) method. Further steps of analysis such as coherence calculations are less distorted after