Modifications of cortical activity by deep brain stimulation in advanced Parkinson’s disease : an MEG study

Tutkimustuotos: OpinnäyteVäitöskirjaArtikkelikokoelma


The aims of this PhD research were to study the feasibility of magnetoencephalography (MEG) measurements in patients with advanced Parkinson's disease (PD) treated with deep brain stimulation (DBS) of the subthalamic nucleus (STN), and to cast light onto the effects of DBS on the electrical activity of the brain. The sensitivity of MEG to magnetic fields makes the measurements of patients using electrical devices challenging because of confounding artifacts. One aim was to investigate how an artifact suppression method called spatiotemporal signal space separation (tSSS) works in the suppression of DBS artifacts. The measured MEG signals included evoked responses, spontaneous brain activity and cortico-muscular coherence (CMC) in DBS-treated PD patients. A total of 24 PD patients were included in the studies. The effect of STN-DBS was measured with DBS first being on and then turned off. CMC and corticokinematic coherence (CKC) were studied in 10 healthy subjects. The motor task for CMC and CKC was to hold the dorsiflexion of the wrist. For CMC recordings, MEG was recorded simultaneously with surface EMG over the activated extensor carpi radialis muscle. The healthy volunteers had an accelerometer sensor attached to their index fingernail for the CKC measurements. The DBS artifact reduction by tSSS enabled a reliable MEG signal analysis for most patients. The effects of DBS on the brain's electrical activity varied considerably between patients. AEF N100m amplitude increased in the right hemisphere for ipsilateral stimulation during DBS. When the DBS was on and eyes open, the source strength of the sensorimotor spontaneous MEG in the 6 10 Hz and 12 20 Hz bands correlated with the UPDRS rigidity measures. No systematic increase in CMC in the 13 25 Hz band during DBS was observed. The patients that had CMC also had the best UPDRS motor scores. The source locations of CMC and CKC in healthy subjects were overlapping and their spectral profiles resembled each other. tSSS is useful in the artifact suppression in the MEG measurements of DBS patients. Despite this, the MEG measurements of DBS patients are still challenging and need exact planning of the experimental setups and caution in the data analysis. DBS modifies cortical electrical activity, and some of these modifications correlate with the clinical improvement in PD. The accelerometer device may turn out to be a good alternative to EMG for coherence calculations even during hold tasks.
Painoksen ISBN978-951-51-1609-3
Sähköinen ISBN978-951-51-1610-9
TilaJulkaistu - 2015
OKM-julkaisutyyppiG5 Tohtorinväitöskirja (artikkeli)


M1 - 90 s. + liitteet
Helsingin yliopisto


  • 3124 Neurologia ja psykiatria

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