title: Optimized beamforming for simultaneous MEG and intracranial local field potential recordings in deep brain stimulation patients.
abstract: Insight into how brain structures interact is critical for understanding the principles of functional brain architectures and may lead to better diagnosis and therapy for neuropsychiatric disorders. We recorded, simultaneously, magnetoencephalographic (MEG) signals and subcortical local field potentials (LFP) in a Parkinson's disease (PD) patient with bilateral deep brain stimulation (DBS) electrodes in the subthalamic nucleus (STN). These recordings offer a unique opportunity to characterize interactions between the subcortical structures and the neocortex. However, high-amplitude artefacts appeared in the MEG. These artefacts originated from the percutaneous extension wire, rather than from the actual DBS electrode and were locked to the heart beat. In this work, we show that MEG beamforming is capable of suppressing these artefacts and quantify the optimal regularization required. We demonstrate how beamforming makes it possible to localize cortical regions whose activity is coherent with the STN-LFP, extract artefact-free virtual electrode time-series from regions of interest and localize cortical areas exhibiting specific task-related power changes. This furnishes results that are consistent with previously reported results using artefact-free MEG data. Our findings demonstrate that physiologically meaningful information can be extracted from heavily contaminated MEG signals and pave the way for further analysis of combined MEG-LFP recordings in DBS patients.
authors.affiliation: UCL Institute of Neurology, Queen Square, WC1N 3BG, London, UK. v.litvak@ion.ucl.ac.uk
authors.forename: Vladimir
authors.initials: V
authors.lastname: Litvak
authors.forename: Alexandre
authors.initials: A
authors.lastname: Eusebio
authors.forename: Ashwani
authors.initials: A
authors.lastname: Jha
authors.forename: Robert
authors.initials: R
authors.lastname: Oostenveld
authors.forename: Gareth R
authors.initials: GR
authors.lastname: Barnes
authors.forename: William D
authors.initials: WD
authors.lastname: Penny
authors.forename: Ludvic
authors.initials: L
authors.lastname: Zrinzo
authors.forename: Marwan I
authors.initials: MI
authors.lastname: Hariz
authors.forename: Patricia
authors.initials: P
authors.lastname: Limousin
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Friston
authors.forename: Peter
authors.initials: P
authors.lastname: Brown
mesh_terms: D000328:Adult; D016477:Artifacts; D001921:Brain / Q000503:physiopathology*; D002540:Cerebral Cortex; D046690:Deep Brain Stimulation / Q000295:instrumentation; D004567:Electrodes, Implanted; D005385:Fingers / Q000502:physiology; D006321:Heart / Q000502:physiology; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology; D010300:Parkinson Disease / Q000503:physiopathology / Q000628:therapy; D012815:Signal Processing, Computer-Assisted; D020531:Subthalamic Nucleus / Q000503:physiopathology*