Simultaneous magnetoencephalography and subthalamic local field potential recordings in Parkinson patients
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AbstractInsight into how brain structures interact is critical for understanding the principles of brain function and may lead to better diagnosis and therapy. To study interactions between the cortex and deep brain structures (basal ganglia and the thalamus) we recorded, simultaneously, local field potentials (LFPs) from deep brain stimulation (DBS) electrodes and magnetoencephalographic (MEG) signals from the cerebral cortex (CTF 275 channel system) from Parkinson's disease (PD) patients with bilateral DBS electrodes in the subthalamic nucleus (STN). High-amplitude artefacts in the MEG, originating from slight movements of ferromagnetic parts of the electrode, pose a challenge to conventional analysis methods. However, we found that beamforming is capable of effectively suppressing these artefacts. We, therefore, used beamforming to obtain artefact-free source recordings from cortical areas whose activity is modulated by movement. Time-frequency analysis of the source data around finger movements revealed power dynamics consistent with previously published findings including event-related desynchronization followed by synchronization in the alpha and beta bands and high gamma activity around the time of movement in both motor cortex (M1) and STN. However, the effect of movement complexity on cortical and STN activity was not the same, indicating that the dynamics of M1 and STN are at least partially independent. We were also able to localize brain areas coherent with the STN-LFP signal and based on a large group of patients it seems that beta oscillations in the STN are specifically coherent with the ipsilateral premotor, superior frontal and inferior frontal areas.